CHIRPS Reality Checks

CHIRPS v2.0 monthly Reality Checks

CHIRPS Reality Checks (rchecks) occur across the many steps to create CHIRPS and on the final product itself.

Background

A team of data analysts routinely quality check each month’s CHIRPS data before its release. This page documents major points of these Reality Checks. The Rchecks Highlights section contains information that CHIRPS users may find helpful, for example, notes about major rainfall events shown by the data and validation for some.

Rcheck is a hands-on approach that helps enable a quality product for hazards monitoring and other scientific activities. In Reality Checks we examine the data visually via the Early Warning Explorer and separately using calculated statistics. Ancillary information, such as FEWS NET datasets, news reports, and government meteorological reports, are frequently used in the process. Rchecks has been successful in: 1) Validating anomalous wet and dry events around that world as shown by CHIRPS, 2) catching inaccurate station reports that would have otherwise negatively influenced the dataset, such as creating false droughts, 3) checking that the semi-automated flow CHIRPS data creation is working correctly, 4) identifying weaknesses and strengths of the algorithm and data inputs, which helps in planning improvements in future versions.

Historic vs Operational rchecks

There are two basic types of rchecks: historic and operational.

• Historical: Historic looks across the whole timeseries of CHIRPS (1981-present)

• Operational: Operational is designed to spot check our products are they are produced.
  • Does this station value fall within expected range?
  • Do the anomaly fields have a reasonable distribution? (not all negative)

View individual stations time series

• The center pixel of the station's 11x11 pixel representation is assigned the anchor station's sequence number in the CSCD1 database. Clicking on this pixel in the EWX will list the seqnum in the lower left corner of the map pane. Note that this may not be the station that was actually used if there was missing data and a nearby station filled in the value. The source seqnum of the station can be obtained with the follow SQL command:
  • select * from station where seqnum=xxx
  • then the source seqnum can be used to get the name of the source like this:
  • select * from source where seqnum=xxx
  • then precipitation table can be selected from the following list of precip tables:
  • daily_precip_conagua
  • daily_precip_fgsod
  • daily_precip_fits
  • daily_precip_ghcn
  • daily_precip_ideam
  • daily_precip_sasscal
  • then the following command will return the station time series:
  • select * from daily_precip_sasscal where station_seqnum=xxx order by date desc
  • Note that the filled value is the precipitation value that is used in CHIRPS. This is the sum of the daily "value" column with any missing data filled in with the mean of the values that do exist in the table.

Helpful Links

Legend for Reality Check station icons

The following are resources that are helpful for conducting monthly CHIRPS Reality Checks. These include links to CHC resources (e.g. data viewers & details from Rchecks) and other products that are used for comparisons.

CHC resources

• *** R Checks STATION WATCHLIST ***
• CHIRPS station locations by country
• EWX viewer

Global products

• Global PERSIANN data viewer Suggestion: Compare CHIRPS to Monthly PERSIANN, PERSIANN-CCS, and PERSIANN-CDR totals

• Global Accuweather rainfall stations Suggestion: Search for a nearby city and the click the month button, then select the month and then the settings button (last on right) to see daily precip totals

• Global NOAA Climate Products: Choose zone of the world for special products (Central Asia, South Asia, Africa, Central America & Caribbean)
• Global FEWS Data Portal
• WMO Links to other National Met Services:
• Climate-Data.org Website with climatology info. Googling a city name + climatology might be helpful also

Africa products

• Africa FEWS Archived Hazards/Threats
• East Africa IGAD website Useful for Rchecks in Greater Horn of Africa. See dekadal or monthly bulletins from Climate Monitoring tab. These are based on CHIRP data that ICPAC blends with more GHA stations than CHIRPS currently has (except maybe Ethiopia- NMA gives > 30 stations to CHIRP)
• Kenya Kenya Met Department Station reports by dekad
• Ethiopia NMA Maproom
• Senegal ANACIM: Seasonal rainfall accumulation Seasonal rainfall anomaly

Central and South America products

• Central America and Caribbean CMORPH precipitation and more
• South America CMORPH precipitation and more
• Central America FEWS Archived Hazards/Threats
• Brazil INMET: Click the Mapas de Precipitacao tab and then the Plus button at the bottom of the map and an end date and time period can be selected (30 dias).
• Argentine Servicio Meteorologico Nacional: Click on Precipitacion Observada or Precipitación Estimada links.

Asia products

• South Asia RFE2.0 precipitation and more
• Pakistan National Drought Monitoring Centre: Maps of monthly rainfall, anomalies, and SPI to compare to.
• India CRIS from India Met Dept: Variety of products. Rainfall graphs helpful b/c many maps show cumulative rains over month+ periods.

Rchecks Highlights

October 2020

Southern Africa data CHIRPS October 2020 data is wetter than is indicated by numerous stations reports in part of eastern South Africa. Users of CHIRPS preliminary data will notice that CHIRPS final is much wetter than preliminary data. See here for a snapshot of October 2020 anomaly from these datasets: from left to right, CHIRPS preliminary, CHIRPS final with station anomalies indicated in the overlaid boxes, and CHIRPS final. The 'wetting' in CHIRPS final in Mozambique is in line with stations reports in Mozambique that were included in final data (and not in preliminary data). These stations are in line with reports of flooding in the provinces of Niassa, Nampula, Zambézia and Manica and in Maputo city. Wetting in eastern Zimbabwe is probably coming from the wet Mozambique observations too. Something also shown by the data comparison snapshot, is that in east central South Africa most of the stations report below average rainfall, like preliminary and other datasets, but CHIRPS final shows above average. This issue could be related to one or more things, and is currently unresolved. One factor could be that local or regional wet station(s) are having a disproportional, primary influence in the blending procedure in this area. Preliminary data from the South African Weather Service also show a much drier October than does CHIRPS final in east central South Africa, shown here. CHIRPS users should thus be cautious about the wet conditions shown by the CHIRPS final data in that area.

September 2020

New station sources have been added to CHIRPS Two new sources of in situ rainfall observations were implemented in this month's CHIRPS, Brazil-Cemaden and Costa Rica-IMN. This exciting addition brings the number of sources to fifteen. In addition to global coverage from GHCN-daily, GTS, GSOD, and GHCN-v4, special contributions from national and regional sources are a big reason CHIRPS is able to provide quality rainfall estimates. Special contributions provide enhanced in situ coverage in Southern Africa, Mozambique, Somalia, Ethiopia, Brazil, Chile, Colombia, Panama, Guatemala, Costa Rica, and Mexico. There are plans to include Trans-African HydroMeteorological Observatory (TAHMO) TAMHO reports in the future to increase coverage in Africa.

New source Rchecks This included visual checks and comparisons of reported values to multiple datasets for September 2020. Brazil-Cemaden and Costa Rica-IMN reports passed these checks and were given the green light for including in CHIRPS. Rchecker Seth noted that in Costa Rica, "the 15 new stations seem to be of good data quality and lead to higher estimated rainfall amounts in CHIRPS in mountainous areas." TAMHO reports for Uganda and Kenya are also exciting, given their dense coverage, however it was determined that these receive a longer evaluation period. Specifically, there were numerous reports with very low (< 10mm) rainfall values in Uganda and western Kenya. Much higher rainfall amounts (50-200 mm) were to be expected, according to recent reports from the Kenya Met Department and IGAD ICPAC.

Japan and Korean Peninsula CHIRPS is showing very high rainfall values in the region affected by Typhoon Haishen/Kristine, the first super typhoon of the 2020 Pacific typhoon season. It peaked as a category 4 super typhoon, then at a weaker stage made landfall in southwest Japan and the eastern Korean Peninsula. This powerful storm left 2 dead, 4 missing, and over 100 injured in Japan. Several stations included in CHIRPS registered highly anomalous amounts for the month, including a station on Fukue Island, the southernmost of the Goto islands in Japan (+441.3 mm above average) and in the South Korea coastal city of Gangneung (+475.0 mm above average, 614 mm total). The impact in the region can be seen on CHIRPS September anomaly map here.

Pakistan Although missed by CHIRP, station data provided vital information regarding above-average precipitation in September which contributed to an already heavy, deadly monsoon season in northern and southeastern Pakistan.

United States With 10 major storms, September 2020 was the most active month on record for the Atlantic hurricane season. One of the most damaging storms in the Gulf Coast and Mexico, Tropical Storm Beta, caused over $100 million in damage and a fatality in Texas. CHIRPS for September 2020 shows monthly totals that are far above average (greater than 2 standard deviations from average) in the Florida panhandle, southeast Alabama, southwest Georgia, and central-northeast Texas. Meanwhile, CHIRPS shows extreme low September rainfall in the upper Northeastern United States, where drought conditions are ongoing. Similarly, much of the West and Great Plains regions and central-south Canada had a much drier than average September. The West is under Extreme to Exceptional Drought conditions. The latest US Drought Monitor can be viewed here.

Africa dataset differences Rchecks observed there are very large differences between CHIRPS and NOAA ARC2, and compared these to other data. CHIRPS, TAMSAT, and PERSIANN show a band of generally above average rainfall in the Sahel region and parts of northern and western East Africa, and below average and mixed condition rainfall equatorward and for a large part of Central Africa. ARC2 is wildly different, with that data showing highly above average rainfall across nearly all of these areas. Comparison of datasets can be viewed at the following links. Map of September 2020 rainfall TOTAL and ANOMALY. (Top-left, CHIRPS; Top-right, ARC2; bottom-left, TAMSAT, bottom-right, PERSIANN)

Rchecks plots New highs for CHIRPS-CHIRP mean in Africa and Sahel but not extreme: eog /home/chc-data-out/products/CHIRPS-2.0/diagnostics/rchecks/monthly_compares/chirps.*.stats.2020.09.png

Contributors: Marty Landsfeld, Seth Peterson, Will Turner, Austin Sonnier, Laura Harrison, Pete Peterson

July 2020

Ethiopia Very large station values, several over or near 500mm, but they are in good agreement with PERSIANN-CCS. Brazil The dry season is very dry in Northern Argentina and southern Brazil, many stations have 0 values. CHIRP was already quite low, but station data lowers values for CHIRPs. Chili The CMORPH product is showing a lot of rain, ~300mm, in the Atacama desert whereas CHIRPs shows near 0 values. Rchecks Plots All statistics look reasonable. There was tie for the low value for CHIRPS standard deviation in Latin America but nothing extraordinary.

Contributors: Marty Landsfeld, Seth Peterson, Will Turner, Austin Sonnier, Pete Peterson

August 2020

China CHIRPS data shows impact of Typhoon Higos, which made landfall in southeast China at the coastal city of Zhuhai. More on Higos here. The signature of the typhoon on rainfall was localized, and it contrasts with the otherwise drier than average August in the greater southeast China region shown in CHIRPS. For instance, in Zhuhai, and the area closely surrounding it, a report shows 190 mm above average while just under 175 kilometers inland, reported anomalies are -51 mm to -121.9 mm.

North Korea and South Korea CHIRPS is depicting observed extreme rainfall in North Korea and South Korea. The events led to fatalities and flooding and major damage to farmland, homes, and infrastructure. More here. There are ~15 stations reporting heavy, highly above average rainfall in North Korea and northern South Korea. Some of these in northern North Korea report >1000mm! Unable to check the accuracy of those, and of course they influence CHIRPS, but the CHIRPS values seem fine (albeit very large). The outcome on CHIRPS is that stations increased CHIRP anomalies to around 2x CHIRP.

India and Pakistan Pakistan and western India experienced extremely heavy rains and catastrophic flooding. More here and here. CHIRPS Rchecks for August displays station anomalies as high as 703.7 mm in west India and 416 mm in southeast Pakistan.

United States Station values significantly increased CHIRPS estimates along the eastern seaboard while decreasing estimates in midwest and northwestern quarter of the country.

Mexico Quality check on what CHIRPS shows in southern Mexico (Pacific coast): Noticed that stations are quite high compared to CHIRP, which shows moderate precip. This produced comparatively much higher values in CHIRPS, which better matches CMORPH estimates.

South Sudan Interesting that ARC2 shows a strong wetter than average August while CHIRPS, CHIRP, and PERSIANN show below average rainfall in much of eastern and central South Sudan. TAMSAT shows a mixed and mainly wet signal there. More analysis could be done to gauge if CHIRPS is wrong or right, but either way there are no stations to discuss removing there.

Rchecks plots All statistics are within normal ranges. The Africa Long Horn set a new high for mean z-score but marginally at less than 0.5.

Contributors: Marty Landsfeld, Seth Peterson, Will Turner, Austin Sonnier, Laura Harrison, Pete Peterson

July 2020

Ethiopia Very large station values, several over or near 500mm, but they are in good agreement with PERSIANN-CCS. Brazil The dry season is very dry in Northern Argentina and southern Brazil, many stations have 0 values. CHIRP was already quite low, but station data lowers values for CHIRPs. Chili The CMORPH product is showing a lot of rain, ~300mm, in the Atacama desert whereas CHIRPs shows near 0 values. Rchecks Plots All statistics look reasonable. There was tie for the low value for CHIRPS standard deviation in Latin America but nothing extraordinary.

Contributors: Marty Landsfeld, Seth Peterson, Will Turner, Austin Sonnier, Pete Peterson

June 2020

Madagascar Here is an identified issue with the existing climatology that CHIRP(S) is built around, known as CHPclim, which is causing artifacts in CHIRP, Prelim, and CHIRPS. The new CHPclim is approaching final stages of production, and appears to perform considerably better in this area. Correspondingly, these artifacts will likely be corrected for in CHIRPS 3.0 (release date pending).

Japan Heavy flooding in southern Japan in the news. CHIRP estimated fairly high rainfall but with the addition of stations, the CHIRPs prediction got boosted.

India Station data shows more rainfall than CHIRP. CHIRPS is more accurate but some lower elevation stations having lower rainfall are mitigating the predictions of higher rainfall at higher elevations.

North America Station values reversed a CHIRP estimated dry anomaly in the Pacific NW to become a wet anomaly from the Cascades westward.

Rchecks plots All statistics look reasonable. There was tie for the CHIRPS Max value and Anomaly Max for Southern Africa which were examined and determined to be from an artifact in CHPClim.

Contributors: Marty Landsfeld, Seth Peterson, Will Turner, Austin Sonnier, Pete Peterson

May 2020

Kenya Stations report continued above average rainfall and flooding in the north and central regions of Kenya in early to mid-May. A total of 161,000 households (over 800,000 people) have now been affected across the country. http://floodlist.com/africa/kenya-floods-north-central-regions-may-2020

Caribbean For some reason, in this month, the station part of the CHIRPS algorithm seems to be breaking down for islands. In Cuba, Hispaniola, Hainan Island (also inland central vietnam) there are big differences between CHIRP and rchecks due to stations that are quite a ways away from the area that changes. There are no stations where the changes occur.

Vietnam An area of moderately high precip in CHIRP (and RFE2) gets boosted to over 600-700mm, for no apparent reason.

China Moderate precip in interior of Hainan island in CHIRPS drops 100mm in rchecks because of stations in lowlands on the island.

Rchecks plots A new low CHIRPS - CHIRP for Africa but only slightly. Very low values in most variables reflects the extreme dryness in Haiti

Contributors: Marty Landsfeld, Will Turner, Seth Peterson, Pete Peterson

April 2020

South America In western Amazonia, confluence of Brazil, Oeru, Columbia, is a very large change in Rchecks (lower precip) over a large area that is based on stations quite a distance away, seems less ideal. In SW Amazonia the opposite happens, there is a very large increase in precipitation that is based on sparse stations.

Iran Heavy rainfall in mid-April created flash floods and swollen rivers in several Iranian provinces, including Kerman and Sistan and Balouchestan in the southern parts of the country.

Rchecks plots A new high for CHIRPS Max in the Long Horn of Africa. Nearly double the previous high for the region. This translated into new high CHIRPS max in Africa and globally, but not drastically.

Contributors: Marty Landsfeld, Will Turner, Seth Peterson, Pete Peterson

March 2020

Eastern Africa Above average rainfall and flash floods in early-to-mid-March resulted in tens of deaths and left thuousands displaced across the D.R. Congo, Rwanda, Burundi, Tanzania, and Kenya http://floodlist.com/africa/drcongo-floods-maniema-march-2020 http://floodlist.com/africa/burundi-heavy-rain-floods-march-2020 http://floodlist.com/africa/rwanda-floods-march-2020 http://floodlist.com/africa/kenya-floods-busia-siaya-march-2020

Madagascar Despite a lack of stations, CHIRPS accurately captures significant rainfall over northeastern Madagascar, which reported flooding in mid-March from Tropical Cyclone Herold. http://floodlist.com/africa/madagascar-tropical-cyclone-herold-march-2020

Rchecks plots New low in CHIRPS mean for Latin and Central America by a large amount, > 5 mm. Also, New low in CHIRPS Z-scrore mean for Latin and Central America by a small amount. Z-scores confirm this with much of the regioin well below normal. This extends well into South America and the southern US. Also, PERSIANN and CMORPH confirm the abnormal dryness. See: http://data.chc.ucsb.edu/products/CHIRPS-2.0/diagnostics/rchecks/monthly_compares/chirps.lat_amer.stats.2020.03.png

Contributors: Marty Landsfeld, Will Turner, Seth Peterson, Pete Peterson

February 2020

Ethiopia Ethiopia CHIRPS data has improved station density, thanks to support from the Ethiopia NMA. There were approximately 100 stations in February 2020 CHIRPS data. This is around two times more stations than in recent data. These stations corroborated and enhanced a weak dry signal also shown by CHIRP in February 2020 rainfall in central Ethiopia.

Australia CHIRPS data shows the much needed rain that eastern Australia finally got in February. The bush fires ended last month after 200+ days of burning, see article here.

Southeast Asia CHIRPS shows a stronger (but still low magnitude) below average signal compared to CHIRP in Thailand and Laos. This is due to reports from numerous stations in both countries

India CHIRPS shows above average rainfall in central east, whereas CHIRPS shows a much weaker signal. This is due to reports from ~6 stations in that area.

Ecuador Higher than normal station values in the rainshadow of mountain ranges caused the values at the mountain ridges to double from 300 to 600 mm. Not ideal. However in Columbia there were a couple of stations near the ridge that were in the 400-500 range so perhaps it's ok.

North America Southern CA had virtually no rain in February 2020 yet CHIRPS is showing estimates in the mountains of over an inch. Big Bear CA station measured zero rainfall, CHIRPS estimated 37.7mm.

CHIRPS processing In recent weeks the team investigated impacts of the two-step station blending process, which is currently a processing step designed to incorporate more recently acquired stations. This showed examples where having the 2nd step resulted in reports farther away than closer stations being blended in the second step and having a substantial influence on CHIRPS estimates. Based on the results of the investigation, Rchecks team is strongly recommending that future CHIRPS processing uses a single pass blending step.

CHIRPS processing Southern Africa CHIRPS data received additional attention in this rcheck. The final version of CHIRPS appears much improved from the first version seen during rchecks. In the first version, the data appeared excessively low in Zambia and Zimbabwe area despite some areas having actually received ample February rainfall. Three SASCAL stations with unrealistic low values were identified- these were the same problem stations identified during rchecks of other recent data. This time these stations were removed from February 2020 data and also permanently removed from future data. The second version of data (after these were removed) showed much more realistic CHIRPS estimates in that area. An odd circular excess wet feature remained, affecting Mozambique and southern Zimbabwe, and it was shown to be due to lack of local stations and influence of stations in South Africa. This was improved by omitting those stations. The result was still realistic estimates in South Africa (where there was high station density even without these) and realistic estimates in the Mozambique and southern Zimbabwe areas. Comparisons to CHIRP and ARC2 data, and previous knowledge from regional rainfall monitoring, were helpful in identifying the problems in pre-final CHIRPS and in confirming that the final, public-released February 2020 CHIRPS looks fine.

Rchecks plots All plots look good and new values fall within historical ranges. There was a new low for CHIRPS Maximum over Africa but just barely.

Contributors: Laura Harrison, Marty Landsfeld, Will Turner, Seth Peterson, Pete Peterson

January 2020

South America In general, pretty good agreement between CHIRP and CMORPH datasets.

Costa Rica Pretty sure this happened last month, too, low values on the leeward side of the country cause areas in Rchecks to have much lower values than CHIRP on the windward side (NE part of CR).

Nicaragua Odd very low rain features in rainfall SE of country near coast. Appears to be in climatology because repeats in other months.

North America Stations greatly increased the CHIRPS estimate in the Pacific NW by a factor of 8 from CHIRP. CHIRPS looks good around Santa Barbara.

Armenia and Azerbaijan We have become aware of a station reporting / CHIRPS measurement issue in Armenia and Azerbaijan. We believe that some stations are reporting solely rainfall measurements, while others are reporting snowfall. As rainfall is roughly one tenth of the snowfall amount, this leads to relatively low CHIRPS precipitation values. CHIRPS values in this area should be interpreted carefully, as the rainfall representation is likely inflated, and the snowfall representation is significantly deflated. In the attempt to make the most accurate precipitation dataset possible, this issue is on our radar and will be addressed soon. Thank you for understanding.

Australia and Indonesia Stations generally show same pattern in anomaly as CHIRPS, which is good to see for that satellite-based product. In Indonesia stations bumped up localized rainfall amounts in several areas.

Afghanistan, India, Pakistan Stations made big difference increasing CHIRP values. The wetter than average signal is coming from 20+ stations in the region, so it seems believable.

Thailand Very nice station density in this country. 25+ stations all showing mild drier than average signal. CHIRP was near average. CHIRPS seems to meet halfway, showing very mild deficits.

Rchecks plots Plot comparisons look normal. There is a new CHIRPS Max high for the Africa Long Horn but (~550mm) but just barely higher than the previous high

Contributors: Laura Harrison, Marty Landsfeld, Seth Peterson, Austin Sonnier, Will Turner, Sari Blakeley, Pete Peterson

December 2019

Australia and Indonesia CHIRPS shows below average December rainfall in most of Australia and Indonesia. Largest deficits are in the 100-200mm range. According to Australia's Bureau of Meteorology, December 2019 had the lowest rainfall on record for the country as a whole and "rainfall was in the lowest 10% of historical observations for much of the eastern mainland and north of the Northern Territory. (link)" We did not examine CHIRPS historical ranks but these are areas with large anomalies and negative z-scores. A big reason for agreement with BoM would be that CHIRPS blends in hundreds of stations across the country.

Brunei, Malaysia (island areas), and Indonesia (near Malaysia border) Consistent with reports of flooding from high intensity rain during December, CHIRPS shows above average December totals (100mm-200mm anomalies). The rain event led to flooding and evacuation of several hundred people. (link to report). In this area several stations reported very high values (~600mm), which increased CHIRPS compared to CHIRP. The flood report and consistency between stations supports the wet CHIRPS signal there.

Zimbabwe Large deficits in CHIRPS across the country. In northern and western Zimbabwe, we note that the CHIRPS anomaly map indicates a larger dry signal in those areas than does CHIRP. This corresponds to CHIRPS values being lower than CHIRP values (by around 20 mm). We remind users that there are no stations in Zimbabwe being blended into CHIRPS, and as usual this results in uncertainty in the data there. Values are based on stations outside the country being blended into CHIRP. In this case for December 2019 data, Zimbabwe is surrounded by ~20 stations that show below average rainfall. These are in Namibia's Caprivi Strip, Botswana, Zambia, Mozambique, and NE South Africa. Between this and the below average CHIRP signal, the dryness in Zimbabwe indicated by CHIRPS appears reasonable.

Portugal, Spain, and France Once again (~3 months in a row), we see that CHIRP and Prelim underestimated rainfall in parts of Portugal, Spain and France (CHIRPS Final is considerably wetter than both CHIRP and Prelim). We have now seen several months of anomaly disagreement between CHIRP and Final in parts of these 3 countries. For monitoring, users should be aware of this discrepancy between CHIRP/Prelim and CHIRPS Final.

Costa Rica and Panama CHIRPS shows mixed anomalies while CHIRP shows largely above average, prompting some investigation as to the cause and which is correct. Compared both products to CMORPH. CMORPH values on land also show mixed anomalies, and while spatial patterns are not the same as CHIRPS, this aspect makes CMORPH in general was more similar to CHIRPS than CHIRP. CMORPH did show above average rainfall offshore. No problems stations in CHIRPS were identified. In terms of station agreement with CHIRPS values, there are discrepancies along the Caribbean coast. Here, some stations report higher rainfall than CHIRPS. One possibility is that the CHIRPS interpolation is being influenced by stations on the Pacific side, or at least on the other side of the mountains, that have below average rainfall.

Honduras and Nicaragua (1) In eastern Honduras and northeastern Nicaragua CHIRPS shows below average rainfall in December, ranging from deficits of 50mm to 140mm. This is in line with a dry signal also shown by CHIRP, but is more intense. Stations are also playing a role here, but these are not well distributed. One near the coast that shower a report that is much lower than CHIRP, by ~50%, and it may have a role in producing the largest difference between the products. This station reports frequently and was not deemed problematic in this check. (2) In northern Honduras, a similar comment to the one for Costa Rica and Panama. On the north coast of Honduras and the islands CHIRP shows high rain ~300mm. 2 of the stations in this area also show reasonably high rain, so this doesn't seem unreasonable. Also CMORPH shows a blob just offshore of this region. When the other more inland stations are averaged in the values on the north coast of Honduras drop down to ~200mm, probably a bit low.

North America Station values increased the rainfall estimates in the Pacific NW reducing the dry anomalies experienced there this winter. The news also reports dryness in this region, see report here.

CHIRPS processing (1) False zero screening was examined in east Brazil, as CHIRPS diagnostics plots show what looks like a large cluster of stations being excluded for this reason. We compared CHIRPS and this screening map to Brazil INMET's map of December 2019 rainfall. The INMET map showed rain where many of these potential false zero reports had been removed. CHIRPS estimates look similar to INMET estimates in the examined area. False zero screening therefore appeared to be working fine here. (2) Possible problem resulting from 2nd blending step. A 2nd blending is done to incorporate stations added to the database after 2015. In Rchecks it was observed that a station involved in 2nd blending was possibly having more influence on CHIRPS values than closer stations. See 'Zambia (NE) entry' on the watchlist for more information. The impacts of the 2nd blending step should be further examined.

Rchecks plots There was a new high value for CHIRPS in South America of around 1600 mm. Other than that all other stats look fine. http://data.chc.ucsb.edu/products/CHIRPS-2.0/diagnostics/rchecks/monthly_compares/chirps.*.stats.2019.12.png

November 2019

East Africa Highly above average rainfall occurred in East Africa during November 2019, according to CHIRPS Final. Some of the more historically extreme amounts are in Kenya, southern Somalia, southern Ethiopia, Uganda, and northern and coastal Tanzania. Estimates show some areas with 100-300 mm above the long term average for November. In many of these areas CHIRPS Final estimates are higher than CHIRPS Prelim, due to blending of station reports into Final. Despite the increased wetting in Final in some areas, the regional wetter than average signal is consistent with what Prelim had indicated earlier. Extreme wet conditions during October to December 2019 are related to a strong positive Indian Ocean Dipole (IOD) mode and warm ocean temperatures. More explanation about the IOD can be be found in this article by The Weather Channel.

Panama and Honduras Stations being blended created more realistic rainfall estimates, compared to the satellite-based CHIRPS estimates. Assessment based on comparison to CMORPH data and review of CHIRPS (too high) versus several blended station reports.

Portugal, Spain, and France Significant discrepancy observed between CHIRP and CHIRP+Stations (CHIRPS), as stations across northern Portugal and Spain and western France report heavy precipitation for the month of November. According to news reports, much of this precipitation came in the form of snow and thunderstorms.

North America Station measurements reduced the CHIRP estimates along much of the west coast and Sierra Nevada mountains.

CHIRPS processing The GHCN-v2 monthly product was recently replaced by a new version, v4. GHCN-v4 monthly contains thousands more station reports than v2, so it is an exciting in situ source to blend into CHIRPS. Efforts were made to do so for the November 2019 CHIRPS final data, but during Rchecks, a problem with the v4 values was identified. In some regions like East Africa GHCN-v4 monthly values were unrealistically high. The problem may have been caused by a processing error, or something else, and the decided solution was to wait on using this new source until more time could be spent quality checking the data. This new source can be included in the new version of CHIRPS due in 2020.

Rchecks plots Regional statistics did not have any outlier values.

October 2019

East Africa East Africa was very wet in October 2019. According to FEWS NET, flooding has displaced more than 700,000 people in Somalia, Ethiopia, and Kenya since early October See here for the report. CHIRPS October data shows very high amounts in southern Ethiopia, southern Somalia (Bakool, Gedo, and and Bay regions), in Kenya (eastern, central, and western areas), Uganda, and parts of Tanzania (L. Victoria and northeast). Many of these areas show > 200 mm amounts, and localized areas show amounts > 300 mm. In and near Somalia, some of highest amounts are in upstream drainage areas of Juba and Shabelle Rivers, along which major damages related to flooding in populated and agricultural zones have been reported. In this area in particular there are ten station reports from SWALIM that are blended into CHIRPS, and comparison of these reports and CHIRPS estimates shows general agreement between the two. Most CHIRPS estimates are within ~25mm of the reported values near the same location, though CHIRPS estimates are higher than reports in northwest Bay by ~100mm. Both reports and CHIRPS show agreement as to October amounts being higher than average- 1 to 2 standard deviations above average in this part of Somalia. Across much of East Africa, October 2019 CHIRPS values are substantially wetter than average, and many of these are historically prominent at 2 to 3+ standard deviations above average.

Southern Africa CHIRPS shows a moderately drier than average October across a large area of Southern Africa, with larger, more substantial deficits in South Africa and Lesotho. October deficits are between 10 to 20 mm below average in Zimbabwe, Botswana, and parts of southern Mozambique, Zambia, and northeastern Namibia. In eastern South Africa and Lesotho October totals were ~50 mm below average. Of all the countries South Africa has highest station density (from GSOD, GTS, and GHCN monthly), and CHIRPS estimates are close to their reported values. Elsewhere, blended reports from SASSCAL and other sources also show agreement with CHIRPS estimates. It is early in Southern Africa's main period of annual rainfall (October to April) and cropping season, and the deficits outside South Africa and Lesotho were relatively small, but these were a notable departure from past Octobers, with amounts being 1 to 1.5 standard deviation below average and in parts of South Africa, up to 2.5 standard deviations below average.

France Stations blended in CHIRPS captured heavy rainfall in southern France and northern Spain. The town of Béziers, France saw 198mm (nearly 8in) of rain - or about two months' average rainfall - in just six hours on the morning of 10/23. See the BBC article here. Across Spain, Germany, and Switzerland, stations reported an anomalously wet month of October, which was otherwise missed by CHIRP.

Japan CHIRPS October data shows the rainfall impacts of Typhoon Hagibis in Japan. Typhoon Hagibis which made landfall near the Izu Peninsula on October 12, 2019. Once making landfall, Hagibis moved NNE transecting the coast just east of Fukushima. It deposited a significant amount of precipitation along the eastern flank of central Honshu, the largest and most populated island in the Japanese archipelago. According to Accuweather’s documentation of precipitation in Fukushima, on October 13th alone, 19.18 in or approximately 487 mm of rain fell. During Rchecks it was observed that two stations reported markedly lower values than neighbor stations. These reports of approximately 145 mm were at the cities of Fukushima and Yamagata. Compared to their surroundings, which ranged from 295-435 mm, and the well documented torrential downpours resulting from Typhoon Hagibis, these station reports may be underestimates. Overall however, CHIRPS data registered the high amounts coming from a high density network of 60+ stations. CHIRP, the satellite-based part of CHIRPS, also showed above average rainfall but the stations substantially increased estimates and were responsible for more accurate spatial details in CHIRPS compared to CHIRP.

United States CHIRPS data shows plenty of low z-score values in the west, verifying a very dry month as noted by the California Weather Blog.

Central America/Caribbean Cool windward/leeward rainfall effects noted in station data reports in the eastern Caribbean

Southeast Asia October amounts were below average from Myanmar to Taiwan, according to CHIRPS. This signal comes from agreement between CHIRP and stations in Thaliand, southern Vietnam, and Taiwan. Stations tended to increase the size of deficits, compared to CHIRP. Stations and CHIRP in northern Vietnam agreed as to above average amounts there.

India CHIRPS shows most of southern India as wetter than average in October, which exception of in northern Tamil Nadu and some nearby areas. The signal is coming from both CHIRP and stations, though the stations increased CHIRPS amounts compared to CHIRP in most of the wet areas. Their blending also increased estimates in southern CHIRP-deficit areas.

Australia We note a circular feature in CHIRPS in eastern Australia- this is centered on a station report that is substantially wetter than surrounding reports. CHIRP shows marginally above average amounts in area, so the station itself is possibly fine. There is no similar feature visible in the October CHPclim, so it is not coming simply from the CHIRPS climatology, but it is being produced by some aspect of the CHIRPS algorithm. This type of thing can be seen in other months of CHIRPS data in Australia. Ideally this will be corrected in next version of CHIRPS.

Chile/CHIRPS algorithm There appear to be high rainfall totals in the southern Chilean Andes, according to CHIRP, but there are no station reports are in that area. Blending of stations in the central valley, which showed low to moderate amounts, seem to have reduced the high elevation values. Seems like this could be an issue in other parts of the world, though perhaps they are better instrumented. Future formal CHIRPS assessments that may help improve blending strategies would include an examination of CHIRPS accuracy in high elevation/high topography regions. Perhaps elevation trends in the Cascades or Sierra Nevada could be useful to inform the veracity of high elevation estimates in South America. CHIRPS blends a high density station network in Guatemala and may be incorporating numerous new stations in Chile, so topography-related assessments would be useful.

Rchecks Plots New highs for region-average CHIRPS Mean and Z-score mean for the Sahel domain, and for the entire Africa domain, but these are not very far from previous highs.

Contributors: Laura Harrison, Will Turner, Seth Peterson, Austin Sonnier, Marty Landsfeld, Pete Peterson

September 2019

Laos A station in southern Laos captured the heavy rainfall from Tropical Storm Podul and Tropical Depression Kajiki, which hit one after another in the first two weeks of September 2019. More than 580,000 people were impacted and at least 28 died in the resulting floods. See the ReliefWeb article here. CHIRPS data shows high values in this region due to influence from this station and from other stations reporting high amounts located nearby in Thailand. These stations being blended in produced a substantial improvement compared to the satellite-based CHIRP, which did not estimate high amounts or above average September rainfall in the affected area.

India CHIRPS shows high rainfall amounts. These are based on the high amounts reported by stations. Heavy, extreme rainfall has led to flooding and over 100 deaths in India. The 2019 monsoon season has seen the heaviest rainfall in 25 years. See the Washington Post article here.

United States Impact of the Hurricane Imelda that struck Houston, Texas on September 17th and caused record-setting flooding is shown in CHIRPS, though we find that the satellite infrared-based estimate (CHIRP) greatly underestimated rainfall totals. Two stations around the Houston area reported around 15” and 18” rainfall and the CHIRPS blending algorithm did a fine job recreating estimates seen in an Accuweather article (link to article here). However, high values above 10” were underestimated in CHIRPS.

Republic of Congo CHIRPS data shows below average September rainfall. This signal is attributed to several GHCN-v2 monthly stations. We examined these and found they report intermittently, which makes their reports suspect, but given they agreed in direction (below average) they were retained.

Rchecks Plots Besides a new high in Africa region anomaly (slightly higher than previous maximum), all other stats are in the normal range.

Contributors: Laura Harrison, Will Turner, Seth Peterson, Sari Blakeley, Austin Sonnier, Marty Landsfeld, Pete Peterson

August 2019

CHIRP vs. Prelim vs. CHIRPS Final in Africa Notable difference between Prelim and Final in northern Ethiopia. Final still shows below average rainfall but CHIRPS Prelim and CHIRP were substantially drier. This was indicated by the CHC Ethiopia Special Reports on dekadal rainfall (Diego Pedreros and Diriba Korecha) that do an early blending of Ethiopia NMA stations with Prelim. These can be accessed from https://chc.ucsb.edu/monitoring. Good to know that that monitoring information is reliable. It is worth noting that Final is also wetter than Prelim in southwestern Ethiopia with big influence from a couple of wet (above average) stations. Same thing in Sudan. These signals have cross-product agreement- ARC2 also shows above average rains in similar locations. Across much of the Sahel, we notice that CHIRP did not capture some of the localized heavy rains that stations in Final and Prelim show (Prelim has GTS stations). One of the areas that CHIRP did perform well is in northwestern Cote d’Ivoire. CHIRP estimates agree with stations there.

Niger CHIRPS shows higher than average August rain in eastern areas of Niger including east of Maradi and in Zinder and to just past the Chad border. Heavy August rains likely contributed to soil saturation and high river levels that, after further heavy rains in September, contributed to recent flooding events and fatalities. According to a Floodlist report from September, “Meanwhile the number of flood related fatalities in Niger has increased from the 42 reported a few days ago. In a statement of 10 September, government authorities said that that the ongoing floods have now resulted in 57 deaths and affected 132,528 people. Over 12,000 homes have been destroyed and widespread damage caused to crops and livestock. Flooding has affected some areas of Niger since June to July, but has worsened over the last week, with many of those affected in Maradi, Zinder and Agadez, as well as Dosso and the capital Niamey.” Link to article here.

Nigeria CHIRP captured heavy rainfall for the month of August, which was confirmed (and increased in severity) by the stations in CHIRPS. Northeast Nigeria suffered from flash floods throughout August. According to ReliefWeb, "Above-normal volumes of rain and the associated flooding are increasing vulnerabilities and risks in camps for internally displaced persons. An estimated 21,056 households have been affected by torrential rains and flash floods across Borno, Adamawa, and Yobe (BAY) states." Link to article here.

India CHIRPS stations captured the extreme rainfall events that occurred in southwest India (these were not identified by CHIRP). According to AccuWeather, “Nearly 227,000 people are seeking shelter from the flooding in Karnataka, where 61 people have been killed. Chief Minister B.S. Yeddyurappa told Reuters that the flooding was the worst the state had endured in 45 years.” Link to that report here. Also in line with CHIRPS estimates of highly above average rainfall along the southwestern coast and in central-northwestern India (Madhya Pradesh and Rajasthan) is a report noting that August 2019 rainfall was especially extreme in India (see report here.

CHIRP vs. Prelim vs. Final in Central America Stations in Final enhanced the dry signal seen in CHIRPS in northern Guatemala and some other Central America locations. However, CHIRPS Final looks very similar to CHIRPS Prelim. This is a good thing to see, as monitoring often makes use of Prelim until Final is available (typically the 3rd week of each month). In northern Guatemala the CHIRPS Final values agree well with the numerous station reports that are blended in. Same agreement in southern Mexico. In western Guatemala, as usual there are a ton of stations, and localized variations such as above average rain reports in mountains and mixed anomalies at lower elevations, have trouble coming through. Hard to tell if there is overall under or over estimation there (by Final, compared to stations). It has been proposed to quantify this, as it could help to know if CHIRPS has any clear systematic bias in this and other high station density areas.

Cuba CHIRPS values are clearly influenced in Cuba by a single station with a high rainfall amount. An internet search did not produce explanation for the high amount, but CMORPH data is also higher in this part of Cuba so this station was deemed ok to retain in the CHIRPS data.

Brazil It was noted during Rchecks that, similar to what has previously been seen, the values on the coast south of Salvador are substantially increased from CHIRP to CHIRPS-- they go from 100-200 mm in CHIRP to 300-400 mm in Rchecks despite none of the nearby stations being particularly anomalous.

Rchecks Plots New lows for CHIRPS mean, max, standard dev and z-scores for Haiti. New high for CHIRPS max overall (“Global”) of near 2600 mm but this is not substantially different from previous maximums. A figure showing stats for August 2019 for entire near-global CHIRPS extent can been be seen [/home/ftp_out/products/CHIRPS-2.0/diagnostics/rchecks/monthly_compares/chirps.global.stats.2019.08.png here].

Contributors: Laura Harrison, Will Turner, Seth Peterson, Sari Blakeley, Austin Sonnier, Marty Landsfeld, Pete Peterson

July 2019

Central America July CHIRPS shows below average rainfall across most of Central America. Much of Guatemala, Belize, and El Salvador had deficits of 100-200 mm and totals only reaching between 50-200 mm. 100-200 mm deficits were also in Caribbean side areas of Costa Rica, Honduras and Nicaragua. These areas tend to be wetter and accordingly still received totals of 300-400 mm (and in SW Nicaragua, 450-650 mm). Large deficits were also seen in Panama, and were most pronounced (compared to climatology) in the Azuero peninsula.

Bangladesh Stations reported highly above average rainfall throughout the country. CHIRP also shows above average rainfall but the signal is more amplified in CHIRPS due to the stations. Heavy rainfall was confirmed by a news report that stated the following: "At least 60 000 homes were washed away or damaged in 13 districts across Bangladesh after a heavy monsoon rains hit Bangladesh and neighboring countries over the past week. At least 26 people have been killed and 3 million marooned. Over the past couple of days, rivers overflowed in 122 upazilas, flooding thousands of villages. According to a special flood bulletin issued by the Bangladesh Water Development Board (BWDB) on Thursday, July 18, 2019, rivers Jamuna and Teesta are at levels not seen in 40 years of water level records." -The Watchers (link to article here)

Southeast Asia and Thailand Approximately 30 stations and CHIRP show below average rainfall in Thailand. Stations amplified the CHIRP dry signal. Most of the country is showing deficits-- largest standardized anomalies are -2.5 in some western and other areas. According to a news report by Hawaii Public Radio, Thailand's government says the country is heading for its worst drought in a decade or longer and it is affecting key crop growing regions and water supplies. More on this story and drought in southeast Asia can be accessed here.

South Korea/Japan CHIRP and stations captured heavy rainfall from tropical rainstorm Danas, which drenched the Philippines, Taiwan, South Korea and Japan in mid-July, according to an Accuweather report. Report here

Kenya A GTS station in NW Kenya was omitted from CHIRPS July 2019 Final. This station reported 95 mm which was suspicious given that this area in dry NW Kenya typically receives around 15 mm in July. The report was cross checked against maps in ICPAC dekadal reports for July 2019. These ICPAC reports blend GHA station reports with CHIRP and can be accessed here. According to ICPAC maps, this area did not receive highly anomalous rainfall and the monthly total in that area were around 35mm at maximum.

Mexico Inland of Los Mochis (mainland Mexico, across from La Paz) there is a notable blob (-100 to 150mm) in the anomaly map in the mountains that seems to stem largely from lower elevation stations being below average. Higher elevation stations are only slightly below average.

Italy In Bologna, Italy a station is reading much higher than the neighboring stations and climatology (approximately 9 inches compared to 2 inches). It has a z score of approximately + 4. The station's report was cross referenced with data from Accuweather.com, which reported a monthly total of 1.88 inches with a previously forecast total of 1.5 inches. It seemed that if a highly populated area actually received such anomalous rainfall there would be a report about it, and none was found online. Thus it was recommended that this station report not be included in July CHIRPS.

India There are large differences between CHIRP and CHIRPS in northern areas of India. CHIRPS shows below average but stations show a mixed pattern, with some far northern and northeastern stations reporting highly above average rainfall. Station reports are tending to break up CHIRP negative anomaly areas so that areas with pronounced negative anomalies in CHIRPS are left in eastern India near Bay of Bengal (Orissa) and in a smaller area in northwestern India (Gujarat)

Sudan Unfortunately there were no station reports in CHIRPS data for July in Sudan. This is not atypical, but last month (in June 2019 data) there were ~14 GHCN v2 station reports included.

CHIRPS note 1 In far southern Argentina along the coast, the CHIRPS climatology (CHPclim) has some artifacts that show up in CHIRPS. Here is very high precip in all months (~300-400 mm when surrounding area is ~25mm).

CHIRPS note 2 In Brazil, in this month's CHIRPS, a lower than normal occurrence of duplicated stations was noticed. Also in Brazil, where July climatology is low, there were many more stations than usual (and most with near-zero values), which was interesting. At first a relationship to the false zero screening in CHIRPS processing was hypothesized. We examined Pete Peterson's maps that show false zero screening and also compared July 2019 station and CHIRPS values to the Brazil INMET July 2019 precipitation map (INMET link here). It appeared that the false zero screening was working fine this month. The phenomenon of there being groups of many stations screened in some months and not others, which was clearly shown in the false zero screening maps, was not explained by this examination and would be worth looking into.

Contributors: Laura Harrison, Marty Landsfeld, Seth Peterson, Austin Sonnier, Will Turner, Sari Blakeley, Pete Peterson

June 2019

Global rainfall and temperature It is interesting to compare global June 2019 CHIRPS anomalies to the global June 2019 air temperatures from Climate Science, Awareness and Solutions' monthly Global Temperature Update. A number of global areas saw both higher than normal temperature and lower than normal rainfall in June 2019. These are southern Brazil (~ 100 mm deficits and temperatures 3+ deg Celsius higher than normal), Central America and some of Caribbean (50-150 mm deficits and temperature 1-2 deg C higher than normal), much of western Europe, West Africa, India and southeast Asia, and in western Australia and northwestern United States. The June 2019 global average was a record high, at +0.93 degC above the 1951-1980 average, and 0.1 degC above the previous record (in 2016). See the June 2019 Global Temperature Update and the CHC EWX to compare.

Sudan High amounts of rainfall and flooding in western Sudan is shown in CHIRPS and is detailed in United Nations Office for the Coordination of Humanitarian Affairs (OCHA) reports: "Flooding in North Darfur has damaged 18 homes in Kebkabiya and 550 homes were destroyed or damaged in Sarafaya village (outside El Fasher). A mission to Tawilla following reports of flooding that occurred on 4 June found 6,198 people in need of assistance. In Leiba, South Darfur, an inter-agency mission identified 325 people affected by flooding caused by torrential rains on 8 June." (Sudan Flash Flood Update No. 8, 20 June 2019 )

Western Europe CHIRPS show below average rainfall in much of western Europe.This signal is coming coming both stations and CHIRP. In Austria the stations showed higher severity of deficits than CHIRP.

Panama All CHIRPS variations (CHIRPS, CHIRP, CHPclim show a North-South swath of high rainfall values. Does not look like a physical rainfall feature. Is also in the preliminary v2 of CHPclim. Would be good to find out what is going on there.

North America Stations often appear to increase estimates in the eastern US. Indication of potential systematic underestimation of rainfall there by CHIRP.

Rchecks Plots New lows for CHIRPS mean, max, std dev and z-scores for Latin America but nothing extreme. New highs for CHIRPS mean and std dev for Africa Long Horn but nothing extreme. New high for CHIRPS Anomaly maximum by ~50% in Sahel. Identified this as being in western Sudan, where there were reports of flooding in June. See entry above.

Contributors: Laura Harrison, Marty Landsfeld, Seth Peterson, Pete Peterson

May 2019

Ethiopia The higher than average precipitation in the southwest is mainly coming from CHIRP (satellite-based estimate) information. Based on comparison to station reports, the CHIRPS final estimates are likely too wet there.

Somalia Rchecker Marty says, "Nice to see no false zeros in the station reports here!" Marty is referring to one of the things we look for during the pre-release CHIRPS Final Reality Checks. Occasionally we notice cases when a station reports a zero value that is highly at odds with neighboring reports and CHIRP. In such cases we give the report extra scrutiny, and if deemed likely to be a "false zero," e.g. an inaccurate report, we recommend not including that report in the CHIRPS blending procedure. One of the station reports in southern Somalia was omitted for this reason last month.

Cote D'Ivoire No stations reporting for the second consecutive month

Guatemala Great to see a very high station density (> 50 reports) in Guatemala. Reports generally agree with respect to locations of above and below average in CHIRP, with one exception: along the Pacific coast CHIRPS has an above average signal while CHIRP shows below average. Several stations point in both directions, but it appears that the wet signal there is mainly dominated by a clump of wet stations that are overriding the below average signal in other areas.

Haiti and the Caribbean Haiti now has 3 stations reporting to CHIRPS. CHIRP is very different from CHIRPS. The CHIRPS signal in Haiti (below avg in CHIRPS, mixed in CHIRP) is due to these 3 station reports (2 are below avg, 1 is above avg) but also stations in Dominican Republic (all are below average). Hard to know if CHIRP is wrong or if the difference is due to lack of stations in the discrepancy area. Jamaica and eastern Puerto Rico stations indicate below average rain, while western Puerto Rico and central-east Cuba indicate above average rain.

Italy/Croatia Station reports greatly increased CHIRPS estimates (compared to CHIRP).

Russia In southeastern Russia several stations report highly above average rainfall. CHIRP does as well but stations are more extreme. Given agreement, this feature in CHIRPS may be associated with a potentially interesting event. Did not get a chance to explore it further. If anyone reading this has information, please share it with us!

Myanmar The large magnitude of negative anomalies in CHIRPS seems due to below average reports in the neighboring country (southwestern region of China). CHIRP shows below average in this part of Myanmar but to a lesser magnitude. Overall, a below average signal in the region is supported by numerous stations and by CHIRP (across Myanmar, to north and east across southern China, and to west in Bangladesh and eastern India)

Philippines Impressive agreement between CHIRP and stations with respect to location of above and below average signal on northern islands.

Rchecks Plots New maximum value for Africa of 2504 mm and anomaly of 2000 mm in Tanzania (islands)

Contributors: Laura Harrison, Marty Landsfeld, Seth Peterson, Pete Peterson

April 2019

South Africa CHIRPS captures the torrential rainfall that led to flooding and fatalities in Eastern Cape and KwaZulu-Natal provinces of coastal South Africa. A station in this area reported 464 mm (18 inches!) in April 2019. The flooding was documented in the April 25th FEWS NET Africa Hazards report.

Caribbean CHIRPS shows that the eastern Caribbean has been experiencing below average rainfall and that, in contrast, April was very wet in some eastern areas like the Cayman Islands. According to a Caribbean Drought and Precipitation Monitoring Network Bulletin, "CIMH said that there is concern for most of the Caribbean that the short term drought situation can impact agriculture, as well as the flow in small rivers and streams except in the vicinity of Cuba, the Bahamas, Jamaica and Cayman islands." Link to report here.

Central America CHIRPS has begun receiving and ingesting a large number of stations in Guatemala, which is markedly improving the estimates. See here for an example of how CHIRPS Prelim for April compares to the pre-release Final, with stations overlaid and the resulting product. In this figure the middle panel shows where stations are located (by pronounced boxes and symbols) and how their reports compare to historical average rainfall. Nice to see sub national variations in the result, due wholly to these stations. In combination with other station data contributions, such as in Panama (see February wiki entry) and Mexico, station density is certainly looking better in this region.

Europe CHIRP largely underestimated rainfall for the month of April. Stations contributed a great deal to capturing multiple storms across Europe and improved CHIRPS.

Portugal/Spain Stations capture widespread wet April across northwestern Portugal/Spain and southern Spain, which was missed by CHIRP.

Switzerland Stations capture extremely wet April across southern Switzerland, which was missed by CHIRP.

USA Station measurements revealed large area of negative anomalies and z-scores. This reversed the CHIRP estimates in Colorado.

CHIRPS issue 1 Odd data feature identified during Rchecks that shows poor CHIRPS rainfall estimation can occur where two geostationary satellite paths meet. This is in northeastern India. In this case a station located on the eastern swath had higher than average rainfall and seems to have produced a very enhanced above average rainfall signal in data on the western swath. CHIRP was mildly above average in that area of the western swath. The problem is that CHIRPS had an unrealistic rainfall above vs below average pattern on either side of the swath line. Certainly something funny going on with the data production, and we requested that the above average station be omitted from final CHIRPS as a patch to this problem.

CHIRPS issue 2 We found an interesting example of a station + algorithm issue that affects CHIRPS, CHPclim, and CHPclimv2. In this case there is a long term station that seems to have been included in CHPclim that corresponds to an unrealistic circular feature in the CHIRPS. The station is at the bottom of a valley in Himalayan mountains north of Nepal. It gets rainfall during the Indian monsoon, but is drier than surrounding area. The current CHPclim algorithm reacts to this situation by producing a dry pimple-shaped feature. This appears in CHIRPS. See the white dot in each panel of the figure here. This is a case of CHPclim struggling in extreme topography-- ideally the climatology would have more geographically realistic spatial variations (than a dot!). We will keep an eye out too see if this is a major problem in other areas. It is reminiscent of the 'circle' problems in Brazil CHIRPS data, which was noted in earlier Rchecks wiki entries.

Rchecks Plots New high z-score mean for entire global domain. Large anomaly maximum in Latin America. New low for South American minimum anomaly. Other than these, stats are in normal ranges. For those noted, no pressing need to investigate further before data release.

Contributors: Laura Harrison, Will Turner, Marty Landsfeld, Seth Peterson, Sari Blakeley, Pete Peterson

March 2019

Mozambique, Malawi, NE Zambia, SW Tanzania We normally have reports from two gauges along central Mozambique coast. Neither of these reported for March 2019. Could they have been damaged by Tropical Cyclone Idai? CHIRPS shows above average rainfall from central Mozambique to the north... into Malawi and near NE Zambia-SW Tanzania. Based on comparisons to TAMSAT, PERSIANN, and ARC2, the above average signal is mainly agreed upon by products. The most different product is ARC2, which shows above average rainfall as being less expansive and mainly in Mozambique. Two stations in NE Zambia and SW Tanzania indicate that CHIRPS estimates are too high in that area. The large extent above average signal is mainly coming from CHIRP.

Kenya We inspected two stations using dekadal reports from the Kenya Met Department website: One in Kitale (western Kenya) and one in Wajir (northeastern Kenya). Kitale report from GSOD did not match the KMD reports and was recommended for removal from CHIRPS. Wajir station from GSOD did match and was retained. The Wajir report plus influence from other stations in region prevented a moderate wet signal from appearing in CHIRPS in the NE Kenya to E Somalia area. This wet feature was coming from the CHIRP satellite information. Several other satellite products (TAMSATv3, PERSIANN, and ARC2) also showed a similar wet feature. We have more confidence in the station reports than the satellite information so it was good to see the blending process produced this correction.

Angola In central-west Angola there is a wet feature that produces an above average signal surrounded by an extensive below average signal. This is in direct opposition to nearby SASSCAL stations. CHIRP is the source of this signal. Interestingly, this feature is also seen in TAMSATv3 and PERISIANN CCS. It is much less pronounced in ARC2. Probably has something to do with common satellite information used in CHIRP, TAMSAT, and PERSIANN. Interesting that a similar thing is seen from the satellite products in NE Kenya (see "Kenya" note above).

South Africa We inspected two GTS stations in NE South Africa because they had same value (7.2mm) and low zscores. We compared these reports to reports from AccuWeather website. March Accuweather reports for Rustenburg total to 7.4 mm (<10% of average). So the 7.2mm there looks correct. Accuweather reports for Ermelo total to 17 mm) (<20% of average). Not identical value, but only off by 10mm. % of average is in agreement with the low zscore. Retained both GTS reports in CHIRPS.

Central America and Hispaniola Widespread below average March rainfall (zscores ~ -1) from Mid-Mexico down to northern Columbia. Rainfall has been below average for Central America region since last summer. Likely related to the borderline to moderate level El Nino conditions since then.

Problem with CHPclim in Indonesia CHPclim is the climatology used in CHIRPS. It has large influence on estimated rainfall values. In northern Indonesia (northern Paua Barat province) CHPclim has either near zero or patchy values for December-March. This produces poor quality CHIRPS values. March 2019 is a good example of this. A station is reporting 319 mm but CHIRPS values are around 15 mm.

Australia NE coast of Australia suffers from a high number of multiple counted stations. Will be interesting to see if CHIRPS data changes much in v2.1 which will not include this practice.

Rchecks Plots Latin America average tied lows for CHIRPS mean and z-score means. March 2019 region average is similar to the driest years on record: March 1988 and 1991. 2019 was drier than March 1992 and 2000. Southern Africa came close to the previous low z-score mean. March 2019 region average is similar to March 2013 and a small set of other previously very dry Marchs. Other than that, pretty normal stats.

Contributors: Laura Harrison, Seth Peterson, Marty Landsfeld, Sari Blakeley, Will Turner, Pete Peterson

February 2019

Panama CHIRPS Panama estimates will now include reports from around 23 stations, which is a major improvement from the 3 station reports that previous data relied upon. Since it was the first time including this source, we took a careful look. It looks like good data, and confirmed that northern South America and the Pacific-side of southern Central America were dry this month.

Southern Africa dryness continues Similar to previous months of the 2018-2019 season, February rainfall was below average for a large area of Southern Africa. February deficits are most expansive in western and central areas including southern Angola, Namibia, Botswana, southern Zambia, western Zimbabwe, and central-western South Africa. Parts of northern Mozambique and western Madagascar also were below average in February. In western and central areas named above and also western parts of South Africa's major maize growing area, December to February totals are 0.5 to 2.5 standard deviations below the local 1981-2018 means.

Ethiopia Inclusion of stations resulted in lower CHIRPS values than CHIRP in central and northern Ethiopia. February CHIRPS shows moderately below average rainfall in southern and central areas and moderately above average rainfall in the southwest. When February deficits, early-mid March deficits, and current forecasts for below average rainfall through end of March, plus a pessimistic forecast for April rainfall from some NMME models are considered, there is concern about a poor start and possibly of overall below average rainfall during Ethiopia's Belg season. This is the main season in southern central Ethiopia and pastoralists in that region are highly dependent on February to May rainfall performance.

Mozambique CHIRPS values may be overestimating rainfall in southern coastal Mozambique in Inhambane. Two GSOD stations reported 115mm and 103mm, but CHIRPS values are nearly 3x higher. The issue is probably due to a combination of CHIRP estimates being wetter than average there, influence of a very wet station report in southern Mozambique in Gaza that also deviates far from average, and the way this information is used to produce CHIRPS estimates.

Afghanistan CHIRPS captures extreme rainfall event that led to flooding in Herat in northwestern Afghanistan. A station reported 314mm with a z-score > 3. Given its extreme nature we examined this report carefully and compared to PERSIANN (did not agree with CHIRPS) and RFE2 (agreed with CHIRPS). The report, and CHIRPS values being above average there, are indeed correct: A news report documented extremely heavy rain, the most in over a decade. It caused flooding on Feb 12-13th that resulted in several deaths, traffic accidents, and collapsed houses. Link to article here. Flash floods have been reported in Herat province on March 18th as well...

Papua New Guinea CHIRPS captures flooding in Papua New Guinea, East New Britian province. CHIRPS totals are 300-400mm above average and 800-900mm in total. The accuracy appears solely due to CHIRP, as there are no stations in this area. Link to article is here.

Australia CHIRPS missed a major rain event in Townsville, Australia. While CHIRPS has a large number of Australia stations and these are relatively dense in this region, there is no Townsville station. Many of the neighboring stations and also CHIRP show rainfall deficits. This extreme and localized rain event led to mass farm animal causalities. Link to the report is here.

Madagascar Large (100mm+) deficits in February in northwestern, northeastern, and southeastern areas. Most of the country shows below average rainfall. Exception is central and northern tip. The signal is coming from CHIRP and station reports, with the latter being responsible for the large deficit areas.

India and Nepal PERSIANN and CHIRPs are in agreement about above average rainfall in far northern India, Jammu Kasmir, and Nepal.

Dominica (Caribbean) CHIRP had a high amount of rain across half of the island, but there was nothing in the news, and 2 stations with low totals for February largely corrected things.

U.S. Station significantly increased estimates in California and Oregon and the southern Appalacian regions.

Contributors: Laura Harrison, Seth Peterson, Marty Landsfeld, Sari Blakeley, Will Turner, Pete Peterson

January 2019

Mozambique CHIRPS values are overestimating rainfall in central western Mozambique compared to a GSOD report in central Manica province. The station reports 265 mm but nearby CHIRPS values range from 400-600 mm. CHIRPS anomalies in central MZ are very large, from > 250mm in west to > 400mm above average along the coast. There are several stations in the country that show high amounts and above average rainfall, including in Tete province and along the coast, and CHIRP also shows above average The presence of higher than average rainfall in some areas is thus not disputed, but the concern is it may be overestimated in some due to overdue influence of these stations.

Turkey/Balkan Peninsula Deadly storm slams into the Balkan Peninsula and Turkey at the end of January. Progressed northeastward into Romania and Ukraine. Captured by CHIRP and stations. A link to the news article is here.

Spain Stations capture above average rainfall in northern Spain not captured by CHIRP. Outcome is substantially higher accuracy in final product than the satellite-only product (CHIRP).

Australia Stations did a good job at correcting CHIRP to CHIRPS in Southern Australia. CHIRP showed above average rainfall, where stations showed well below, and final product accounts for that.

Costa Rica Several of us had concern is that 2 stations with reports of 0mm are helping create major large negative anomalies on the Gulf side of the country (compared to CHIRP). The z-score in affected area of Gulf are not extreme, but are large. This is not a case of duplicate station, as is sometimes seen- seqnums indicate these 0mm reports are from two different GSOD stations near to each other. With goal of reducing influence on the Gulf side we requested one of these stations not be included this month.

Caribbean Noted during the checks was that in some islands with a climatologically dry side/wet side, an above average report on the drier side resulted in the wet side being estimated as having a very large anomaly. Consistent with how the algorithm operates (% of normal is interpolated) but it produced an unrealistic outcome here.

Z-scores reminder A reminder to be careful when interpreting z-scores (standardized anomalies) in CHIRPS data in low rainfall regions/periods. These fields are made available to users via the ftp site. In reality checks, z-scores are one field we look to when comparing station values to CHIRPS estimates. Example here is in Myanmar-- There is generally very little rain there at this time of year. Several stations reported 0mm, while CHIRP showed around 4 mm. Yet, by looking at z-scores in the region, if you weren’t careful to look at raw data, the stations overlaid on CHIRPS would look bizarre – exceptionally dry z-score value stations in the midst of an exceptionally wet z-score value CHIRPS field.

Reality Checks overview 21 stations were identified for removal from the final CHIRPS. 9 of these were in Brazil, due in part to the over influence attributed to them by the current CHIRPS processes step that allows for a single station to be counted multiple times. Not all these cases are grounds for station removal, only when they have a noticed and substantial impact on regional anomaly patterns. This problem is due to be fixed in version 2.1.

Contributors: Laura Harrison, Will Turner, Emily Williams, Marty Landsfeld, Seth Peterson, Sari Blakeley, Pete Peterson

December 2018

Missing GCHN-v2 stations US government shutdown may have impacted access to GHCN-v2 stations, which are considered high quality and an important source in CHIRPS. CHIRPS usually incorporates ~1,000 GCHN-v2 reports globally. Station count (all sources) used for December 2018 CHIRPS data is currently ~12,000. When GHCN-v2 become available, December 2018 CHIRPS data will be reprocessed.

Eastern Horn of Africa NOAA ARC2 and CHIRPS data have a different interpretation of December rainfall anomalies in eastern Kenya and southern Somalia. Differences can be seen in the figure here. CHIRPS, which includes ~16 SWALIM stations in southern Somalia, shows southeastern Somalia as above average. ARC2, which has no stations in Somalia, shows a mix of below average and above average here and in eastern Kenya. In eastern Kenya CHIRPS above average. This is primarily coming from CHIRP signal and stations in central Kenya and southern Somalia. The positive anomalies in the eastern Horn in CHIRPS are consistent with the above average rainfall estimated across equatorial East Africa in CHIRPS.

Switzerland and Austria Stations in CHIRPS capture storm that hit Switzerland and Austria during the holidays. A link to that article is here.

Argentina Rchecks has higher precipitation than CHIRP in northern Argentina. A website on commodity crops confirms December was wet. Link to article here.

Southern Africa CHIRPS shows December 2018 rainfall as below average for much of Southern Africa. This is consistent with ongoing monitoring and reports in the region. December rainfall was near or above average in some smaller areas of eastern Botswana and northeastern South Africa. Evaluation of difference between CHIRPS Prelim and Final for Dec 2018: As indicated by comparison of anomaly maps: 1) Final is substantially drier in SW Zambia. 4 stations in this zone; 1 was removed for suspected false zero. 2) Final less dry than Prelim in south-central Angola. 3) Zimbabwe Final and Prelim estimates are similar, except that far western Zimbabwe is drier. 4) Areas in NE South Africa with above average in Prelim are still above average but closer to average now. The comparison can be seen here [Figure link coming soon].

Central America and Hispanola Widespread dryness for the month on both the islands and most of C. Amer. Based on time series plots for the region, December 2018 CHIRPS mean and average z-score was a new low, compared to 1981-2018 data. Evaluation of difference between CHIRPS Prelim and Final for Dec 2018: No big changes in regional anomaly pattern. Both show below average in western region of Central America. CHIRPS is slightly drier than Prelim in Guatemala and slightly different dry anomaly pattern in Nicaragua. In far southeastern Mexico CHIRPS has a more expansive above average area.

West Africa Evaluation of difference between CHIRPS Prelim and Final for Dec 2018. Prelim showed below average near coast; Final shows less dryness and a more mixed pattern across this region.

United States Stations used in CHIRPS significantly increased estimates in the southeastern US. In the western US, a comparison of CHIRPS and Persiann estimates identified there are dramatic differences between these data sets for December 2018 rainfall.

Contributors: Laura Harrison, Marty Landsfeld, Will Turner, Seth Peterson, Sari Blakeley, Pete Peterson

November 2018

Southern Africa The inclusion of station reports into CHIRPS resulted in a (more) negative assessment of November 2018 rainfall across much of southern Africa (compared to CHIRP and CHIRPS Preliminary). See comparison here. CHIRP and CHIRPS Preliminary for November 2018 were already showing deficits across these areas. Numerous stations (~100) from multiple sources (SASSCAL, GTS, GHCN-v2 monthly) indicate substantial deficits in November 2018 for Botswana, South Africa, Lesotho, Namibia, Zambia, Angola, and in southern Madagascar, southern Mozambique, and southern Tanzania. As usual Zimbabwe does not have stations reporting to CHIRPS. A result is that CHIRPS in Zimbabwe is influenced by neighboring country stations and thus CHIRPS deficits are larger than what is shown in CHIRP and CHIRPS Prelim. It is notable that the difference between the southern Africa CHIRPS and CHIRP means is larger (more negative) than for any previous November in CHIRPS record. This also speaks to the value of the SASSCAL contributions to CHIRPS.

Missing GSOD stations For a ~5 day period in late November, thousands of GSOD station reports were not available in the main GSOD data repository. This resulted in only a fraction of the usual reports being considered for inclusion into CHIRPS. The reason being is that with this many missing days, the criteria for >27 days of reports to make a monthly total was not met at thousands of locations. In CHIRPS processing, if other sources e.g. GTS were available, those were used to fill in for missing GSOD monthly totals. This filling-in occurred in many regions. Stations counts in Portugal, France, and Spain were notably lower than normal because of the missing GSOD reports. Portugal normally has ~14 GSOD reports; this month Portugal had 0 GSOD reports and only 1 station report guiding CHIRPS.

Ethiopia The value of Ethiopia NMA's sharing of 50+ stations was clearly shown in November 2018 CHIRPS. CHIRP and CHIRPS Prelim, in central and northern Ethiopia, showed a mixed signal of above and below normal rainfall. Inclusion of numerous NMA stations into CHIRPS changed this signal to show a more widespread pattern of above average rainfall, and with larger positive anomalies.

Central America The stations that were included in CHIRPS show a similar story as did CHIRPS Prelim—- a below average November. See comparison here. It would be ideal to have more stations reporting to CHIRPS in this region, but there are ~30 stations in total for the region from south of Mexico to Caribbean to Panama. For monitoring and early warning it is helpful that these stations in CHIRPS were in general agreement with the low latency CHIRPS Prelim.

Somalia Three station reports were given extra scrutiny due to having reported low values (compared to CHIRPS background estimates). The 2018 Deyr rains have been given careful attention in the FEWS NET community, given deficits being previously reported and estimated. A fruitful Reality Check was to compare daily reports at these stations to daily rainfall time series from NOAA's ARC2 rainfall data. ARC2 does not have stations in Somalia-- we used it as indication of timing and magnitude of potential storms near these scrutinized stations. The comparison yielded support for two of these reports (25mm in Baardheere and 0mm in Mogadishu). The third (0mm) was considered potential false zero and removed from CHIRPS. There are typically ~9 SWALIM stations contributing to CHIRPS estimates in southern Somalia and 30+ SWALIM stations in northern Somalia- making a higher station count in CHIRPS than any other global product.

South America There is a general trend of higher precipitation in the south of the equator ITCZ in CHIRP but the addition of the stations raises the precipitation values a little, bringing them more in line with those from CMORPH. This feature stretches from Peru through western Brazil, northern Bolivia, Paraguay, and a portion of northern Argentina.

California Two erroneous stations identified (Bode and Redwood City). These were removed from CHIRPS. Interesting that CHIRP shows average to below average in central and northern California, and inclusion of stations corrected this to an above average signal.

Sierra Leone Anomaly sign flips in CHIRP vs. CHIRPS, probably due to influence from a wet station in Guinea

India Stations and CHIRPS Prelim both show below average for most of India (~50 stations). Zscores are -0.5 to -1.5.

Japan Below average November rainfall, based on Prelim and stations (~50 stations). Anomalies range from ~-20mm up to large deficits of -100—150mm along the west coast.

Australia Northeastern and eastern coast areas were below average according to Prelim and stations. Through central Australia the stations substantially increased estimated rainfall compared to Prelim, changing that area from average to below average to average to above average.

China In southeast China stations led to a change in anomaly sign. Prelim was showing a mix of below and above average; stations (~30) being included changed CHIRPS to above average in this region.

Indonesia/Papua New Guinea Signal in CHIRPS is different than CHIRPS Prelim, despite there being no station reports on this island. Thus it is due to influence of stations in other areas. The change is that the drier than normal southern areas appear drier in CHIRPS Final, and the wetter than normal northern areas are closer to average or below average in a few locations.

Contributors: Laura Harrison, Marty Landsfeld, Will Turner, Seth Peterson

October 2018

East Africa Given high level of concern about below normal rainfall in the eastern Horn's OND season thus far, and importance of CHIRPS products in monitoring this event, we took care to notice the data in this region. Here are some features: There is a spot in southern Somalia where ARC2 registers high rain total in a small area, but CHIRPS does not. Compared to ARC2 rainfall estimates, CHIRPS shows higher October 2018 rainfall values in the eastern Horn and has a more realistic looking spatial pattern. A previous analysis comparing October 2018 CHIRPS Prelim to SWALIM stations (which are used in CHIRPS Final) showed that reports matched values well in Bay region, where there were concerns about cropping. Closer to Kenya border we have less confidence in CHIRPS values as some areas may have had localized rainfall. In dry areas we have seen CHIRPS struggle with such cases in the past. One of the SWALIM stations in southwestern Somalia reported 0mm for October. ARC2 daily indicated rain in several days, totaling ~20mm for the month, so we took a cautionary route-- we assumed this SWALIM report was a 'false zero' and recommended it not be included in CHIRPS Final. We appreciate FAO SWALIM providing reports early this month-- these were helpful for assessing conditions in the region and providing early warning.

Spain, France, Italy Stations capture heavy storms throughout northern Spain, southern France, and Italy, which left at least 11 dead in Italy and thousands without electricity. The severity of these storms were not originally captured by CHIRP. News reports about Italy storms here and here.

India According to news reports, October 2018 was the driest October in India since 1976. CHIRPS also shows October as being drier than normal for large area of the country-- making it the 2nd month in a row with widespread deficits and 3rd month with deficits in some areas. Sugar cane yield is projected to decrease, and price to increase. This dry spell was captured by CHIRP and supported by station data.

Sri Lanka CHIRP captures devastating flooding in Sri Lanka from early October that left 9 dead and 5,000 displaced.

United States Station values really contributed to CHIRPS in the southern Applachians as well as Texas where flooding was an issue in October.

Western United States CHIRPS anomalies show the continuing drought of the west coast states

Central America and Haiti Below average October rainfall in areas that have experienced rainfall deficits for several months: parts of Guatemala, Honduras, El Salvador, and Haiti. High rain totals and above average signal along Pacific coast, Nicaragua to Costa Rica. CMORPH also shows this. Probably associated with hurricane activity.

South Korea and Japan Really interesting anomaly pattern. South Korea showing anomalous high rainfall across country while Japan shows opposite. Signals are backed by numerous stations.

Southern Africa October 2018 is a new low in terms of how much rainfall occurred in the wettest location of southern Africa (lowest CHIRPS Maximum of 1981-2018). Below average rainfall was seen across much of the region. CHIRPS mean for this region indicates October 2018 is among one of the driest Octobers of 1981-2018.

Kenya During Rchecks we looked into a potentially odd pattern in western Kenya. There were reports of highly above average rain close to reports of below average rain. Compared to the October 2018 ARC2 anomaly map. It shows same pattern.

West Africa CHIRPS shows above normal October rain in Burkina Faso, Niger, and Nigeria. The signal is coming from some numerous station reports and with some agreement from CHIRP. eMODIS NDVI shows higher than normal vegetation productivity in early November in that region. Potentially an outcome of above normal October rains.

Contributors: Laura Harrison, Will Turner, Marty Landsfeld, Sari Blakeley, Seth Peterson

September 2018

Ethiopia CHIRPS Prelim (and CHIRP) were wetter than CHIRPS Final. This is due to influence of average to below average station reports in some areas of NW and much of central Ethiopia that were included in final version of CHIRPS.

Philippines CHIRPS shows very high rainfall in northern Philippines where Typhoon Mangkhut passed through. Heavy rainfall from Mangkhut led to a mudslide that killed at least 66 people. At monthly time scale, CHIRP only picked up on moderate magnitude above normal rainfall, but reports from stations in that area produced large (wetter) values in CHIRPS. An extreme station report is 1220mm for the month; others report 300-500 mm.

Japan CHIRPS shows high amounts of rainfall associated with Typhoon Jebi. This is coming from both CHIRP and station reports.

Cayman Islands There is a co-registration issue with small islands, we can see that the shape of the island in vector format is different from the area that is modeled in CHIRP/CHIRPS. In this month this caused an issue because the station value was compared against a (low) ocean rainfall value rather than a (high) land rainfall value, which caused the already high land value (Tropical Storm Isaac) to become even higher.

Eastern Caribbean Kind of odd, regarding influence of Tropical Storm Kirk on the data: In CHIRP, Barbados has lower rainfall, but the island chain E of it is high rain. From the stations, Barbados got hammered and the island chain was neutral (though stations not positioned the best to capture Kirk effects). In CHIRPS, even with the high station value Barbados rainfall didn't get corrected very much. So this is a different small island phenomenon than for the Caymans. Seems like interpolating from 5 station values is not ideal when rainfall from tropical storms can be so localized.

Costa Rica and Nicaragua CHIRP is quite wet in central, western Costa Rica, and western Nicaragua. CHIRPS (with stations) is quite a bit drier than CHIRP. CMORPH is drier than CHIRP as well.

'Northern India In far northern India, CHIRP and stations showed anomalous high rainfall in Himachal Pradesh Mountains. Station reports (but not CHIRP) showed a wet signal also to the south, and this was carried through into CHIRPS.

India and SE Asia CHIRP and stations show below average rainfall in much of India and many arts of SE Asia. Interesting feature, which we are not sure if is accurate, is an area of above average rainfall in NE India/Bhutan area. Seems to be mainly coming from CHIRP. PERSIAN-CCS also shows below average across this region.

Contributors: Laura Harrison, Will Turner, Seth Peterson, Marty Landsfeld

August 2018

India Northern India recieved higher than average rainfall in August 2018, based on reports of amounts 350mm to 700 mm above normal at several stations in the lower elevation areas of the Himalayas. The wet signal is also shown in PERSIANN-CCS data and CHIRP.

Hawaii Wow! Two stations near Hilo reported 73 and 48 inches of rain in August. That is 4-6 FEET of rain. CHIRPS Prelim did a decent job of showing spatial pattern of enhanced rainfall on that part of the island but the added stations in CHIRPS Final really upped the magnitude. Tropical Storm Lane was responsible for much of the monthly total and produced record breaking rainfall for August. Read the story here

Haiti CHIRPS shows below average August rainfall particularly in southern areas. This signal is coming from CHIRP and possibly also also influence of a substantially below normal (z-score ~2.6) report in southwest DR. Three other stations in DR show below normal (but closer to normal). Haiti has no reporting stations. CHIRPS final similar to CHIRPS Prelim for August 2018.

Brazil Near the coastline south of Salvador, Brazil shows a large increase in rainfall from CHIRP to CHIRPS, going from ~200 to 400mm. However there aren't any visible stations causing this, the only visible stations (in EWX version of CHIRPS Rchecks) have neutral to slightly negative anomalies. Not sure what is going on here.

Liberia There is a spot of low rainfall in central Liberia that stands out as "off." This is present in August CHPclim, teh CHIRPS climatology, and likely the cause.

Sudan No stations reporting in Sudan. Last month there were 14. Previous Rchecks month/years shows the number of stations varies a lot from month to month.

More about RChecks 23 cases were carefully examined during Rchecks, and this led to 10 stations being removed from global August 2018 CHIRPS final data.

Contributors: Laura Harrison, Marty Landsfeld, Sari Blakeley, Seth Peterson

July 2018

Ethiopia Ethiopia CHIRPS data based on > 30 stations. These generally confirm the pattern of below average rainfall in southern, central and northern Ethiopia as shown in CHIRP and CHIRPS Prelim. CHIRPS and stations show above average rainfall in two localized areas: a small zone in central Oromia and at border of Amhara and Afar. The drier than normal July signal is more severe in CHIRPS than CHIRP and Prelim in some areas.

Greece CHIRPS data, due to incorporation of stations, captures series of flash floods towards the end of July, following the deadly wildfires in Athens, Greece.

West Africa coast An area along coast that usually has a station (GTS or GSOD) is not reporting. This results in the countries of Guinea, Sierra Leone, and Liberia having no station reports. End result is that CHIRPS data is mimicking the CHIRP signal and is somewhat influenced by stations outside the area, which lowers confidence in CHIRPS estimates of below average in that area. However, CHIRPS is not the only data showing this dry signal. TAMSAT and PERSIANN data also show below average here. This is a curious area because recent months have also registered as below average in CHIRPS but ARC2 data has been showing the opposite in all except May. July 2018 anomalies from multiple data sets shown here.

Mexico and Central America According to CHIRPS July 2018 rainfall was below average for a large region including central and southern Mexico and through Central America to western Costa Rica. For this region: In comparison to July 2015, the summer of drought leading up to the major 2015/16 El Nino, this July (2018) had lower rainfall in many areas and the spatial extent of the below average precipitation signal appears larger, in part due to much of Mexico being affected in 2018. Comparison of July 2018 (left) to July 2015 (right) CHIRPS here.

Mozambique Multiple stations in Mozambique and southern Malawi report higher than average rainfall in July 2018. To some extent this is supported by ARC2 data, which shows above average rainfall at spots in these areas. The spottiness of ARC2 here is likely problematic for users of that data. In comparison the signal in CHIRPS data is coming from >10 stations of different sources and shows a more geographically expected precipitation pattern. July 2018 data for CHIRPS and ARC2 can be seen here.

Uganda The drier than normal July signal in northern Uganda looks less severe in CHIRPS than CHIRPS Prelim. There are two stations in vicinity (NW Kenya and central Uganda) which both show standardized anomalies of -1.7 and -0.5, respectively). CHIRPS shows standardized anomalies of -0.5 to ~-2 in some areas. Reason for more severe signal in Prelim may be CHIRP and preliminary GTS stations.

Senegal Multiple data sets, including CHIRPS, show below average July 2018 rainfall in western Senegal. July anomalies can be seen here. This area has been highlighted in FEWS NET weekly and seasonal monitoring as an area of concern for poor cropping conditions and potential food security issues.

Switzerland Stations capture continued drought in eastern Switzerland. 'Driest summer for more than a decade'

Serbia Stations capture intense storms and flooding throughout Serbia for the month of July.

Contributors: Laura Harrison, Will Turner, Sari Blakeley, Seth Peterson

June 2018

Haiti and Dominican Republic A station in southern coast of DR was removed from CHIRPS because it seem to have adverse influence in Haiti, where a dry signal was shown by CHIRPS, other stations, and other rainfall and vegetation products. This station reports highly above average rainfall (total 221mm, anom ~130mm). Upon comparison to CMORPH it might be from some on-land influence of an offshore area of above average rainfall (related to storm Beryl?). The value itself is thus believable but the influence seems to be such that precipitation in Haiti is markedly changed from CHIRP anomaly, which shows below average across Hispanola and agrees with CMORPH June anomaly. Drought conditions have been recently reported in Haiti

Kenya CHIRPS in western Kenya show large positive anomalies. While stations to the northwest and southeast do show above average precipitation, there are no stations within the area that has very large positive anomalies. The signal is coming from CHIRP and probably also influence from the stations outside the area, plus the area's higher climatology, as described below in the Columbia and Ecuador entry.

Southern Africa Coastal areas of Southern Africa shows a weak below average precipitation pattern that comes from station reports. These are generally enhancing the signal shown by CHIRP. Interesting that CHIRP anomalies offshore are stronger below average than on land. Together the stations and CHIRP indicate a region-wide drier than average signal.

Columbia and Ecuador Contribution of stations into CHIRPS increases the magnitude of the negative anomaly shown by CHIRP in coastal Ecuador and Columbia. The influence seems to be coming from inland stations that have large negative standardized anomalies. There are no stations on the coast here, and in fact the nearest coastal station, at the northern edge of the coastal area, has a positive anomaly. This case might be a result of a feature of CHIRPS algorithm that applies closest 5 stations' percent of normals to the local pixel's climatology to estimate local precipitation. The climatology in this area is relatively high, which means that a drier than normal signal from elsewhere would be amplified.

India CHIRP shows above average and high rainfall totals along western coast of peninsula. 8 stations along this zone also report very high amounts. The station totals tend to be higher than CHIRP totals, but not in all cases. Result is CHIRPS totals of 750mm-1500mm in this zone, maybe some pixels are even higher than 1500mm.

Mariana Islands CHIRPS estimate of 3270mm here is an all time high CHIRPS value. This is the same island chain that produces extremely high z-score values (10^11). This needs to be investigated and resolved in CHIRPS 3.0.

Afghanistan RFE2 and CHIRPS data in agreement about localized higher than normal precipitation in southeast Afghanistan.

Contributors: Laura Harrison, Marty Landsfeld, Lilian Yang

May 2018

Continuation of wet conditions in some of East Africa CHIRPS May 2018 data shows positive rainfall anomalies in interior areas (from western Kenya north to South Sudan and western central Ethiopia) and eastern areas (coastal Tanzania and Kenya, southern Somalia, and northwest Somalia). This is consistent with flooding and landslide-related disasters, large numbers of displaced people, and many fatalities in some of these areas. In Kenya the number of fatalities is at least 186 people during this extremely wet March to May season.

China (south east) Severe drought continues in south east China (including Hong Kong). CHIRPS May 2018 data shows large magnitude deficits. Subtropical Hong Kong gets an average of 2,400mm of rain a year, about a tenth of which comes in May. But since January this year, less than 170mm has fallen on the city, under half the normal average for this period. Low rainfall, coupled with high heat has begun to deplete reservoirs, which farmers rely on for irrigation. Some crop failure and wilting has been reported.

Guinea and Sierra Leone Substantially below avg. rainfall (~100mm deficits) indicates multiple week delay to growing season rainfall. NDVI anomaly maps had indicated vegetation impacts. More extreme in CHIRPS than CHIRP. Careful though. Biggest signal is in areas without stations but with higher climatology (e.g. central Guinea); surrounding stations are leading to increased deficits in some areas. However, CHIRP does show deficits of ~80mm.

India (southwest coast) CHIRP and stations both capture early monsoon arrival on the southwest coast of India. CHIRP fails to identify deadly storms in northern India (Uttar Pradesh), though they are captured by several stations

Armenia High rainfall amount in CHIRPS confirmed by flooding report

Bangladesh CHIRP and stations both capture devastating floods in Bangladesh

Thailand Stations capture flooding in northern Thailand (Chiang Rai) that caused a fatality

Tasmania CHIRP and stations fail to identify extreme rain events in southeast Tasmania. Rain and thunderstorms brought exceptionally high rainfall to the southeast of Tasmania, in particular to Hobart and the nearby Wellington Range where almost all sites reported their highest May daily rainfall on record. The daily totals of 236.2 mm at kunanyi (Mount Wellington Pinnacle) and 226.4 mm at Leslie Vale are now ranked two and three in the list of highest May daily rainfalls ever recorded in Tasmania.

Ethiopia May CHIRPS shows below avg rainfall through northern and central regions. The signal comes from NMA station reports and CHIRP. The stations enhance the deficits compared to CHIRP but show similar pattern. Rchecks identified that multiple stations (from SWALIM and NMA)indicated dryness in eastern area and that instead of reflecting this, the first version of CHIRPS was showing an above average signal. Further analysis indicated that a single highly anomalous wet station reporting ~300mm from a mountain top in the area, along Somalia border, may have been positively swaying the regional signal. Comparisons were done to dekadal rain totals and anomaly maps from Ethiopia's MapRoom- these did not show such high rainfall. The station was omitted from CHIRPS final based on concern it was casting too much weight. Tropical Cyclone Sagar did pass across parts of northern Somalia, and other remaining anomalous wet stations still show its impact.

Somalia Overall CHIRPS appears to have good estimates for Somalia. Areas of below average rainfall in the eastern Horn (from stations) are showing up in CHIRPS, as are above average rainfall estimates in southern and northern areas. CHIRP is consistent in some of these areas but stations are having clear role. Note that several stations report below average rainfall in southern Somalia and CHIRPS may be overestimating in these areas due to wetter stations nearby. Tropical Cyclone Sagar in early May had some role in heavy rainfall in northern Somalia.

Mozambique There is a single station in coastal central MZ creating a below avg. signal that propagates towards interior. CHIRP does not indicate this. We compared to ARC2 to find that ARC's May 2018 anomalies and May climatology pattern is odd looking (spotty) in southern Africa. There is a large difference between CHIRPS and ARC2 May climatology in this central coast area in particular-- CHPclim shows the area receives from 25-80 mm on average. Hence why the CHIRPS anomaly propagate through this area. The station report was deemed as potentially being accurate-- ARC2 also shows a below average spot there.

Niger There is an incorrect blob of rainfall in northern Niger data, which is usual for May CHIRPS. The feature comes from a wet feature in the climatology (CHPclim) being perturbed by estimated percent of normal to produce CHIRPS estimates. Sometimes remote stations have enough influence to perturb it towards substantial rainfall values, which is what may explain this month's estimates of 25-50mm (+10-25mm anomalies). CHIRP anomalies are close to zero.

Ghana In northern Ghana a positive anomaly at a rain gauge seems responsible for an area of enhanced positive anomaly to its south. Little influence from other rain gauges for explaining this rainfall event, but rather a likely influence of it working with the higher climatology to produce a larger anomaly in that area.

Republic of Congo and DRC The rain gauges are on either side of the border between Republic of Congo and DRC, but they have about 200 mm of rainfall difference. There might be an influence of topography.

Brasil/Argentina/Uruguay There are 3 separate stations in the Iguazu falls area that all show low rainfall. The other stations in the general vicinity and CMORPH all show very high rainfall.

United States In eastern US, CHIRP did not pick up the very heavy rain amounts in the Appalachain mtns but stations corrected that in the CHIRPS product. CHIRPS overestimated rainfall in the Pacific NW but many low value station readings corrected this in the CHIRPS product.

CHIRPS algorithm issues May 2018 data in Kenya has a clear example of why it is problematic to make estimates based on a deviation from monthly climatology when the climatology is near zero. November or October 2017 data had same problem in northwestern Kenya. In May 2018 data two stations, in northern and eastern Kenya (179mm and 48mm), report substantial and highly anomalous rainfall; its is reasonable to think this may have occurred through the climatologically dry corridor in northern to eastern Kenya. CHIRPS estimates however are near zero throughout the whole area, including at the 48mm station location. This is because CHPclim is near zero. CHIRP shows average to below average in the area so there is an odd effect where the stations exhibit highly anomalous wet rainfall (zscores >3) but CHIRPS indicates average to below. Being highly anomalous, it is possible that these stations are influencing estimates elsewhere but it is difficult to detangle their influence from other wet stations across the region.

Other CHIRPS info There were no statistical outliers to report this month. In southern Tanzania, a blocky pattern in anomalies is coming from CHIRP.

Contributors: Laura Harrison, Will Turner, Sari Blakeley, Marty Landsfeld, Seth Peterson

April 2018

East Africa Consistent with reports of much higher than normal rainfall, which led to a number of disasters and impacts in east Africa, CHIRPS shows highly above average rainfall in April 2018. Extreme rains (>100 mm in 24 hrs) and flash flooding were reported on several days in cities across the country, incl. Marsabit (4/13-4/14), Garissa (4/16-4/17), and Kitui (4/23-4/24). Between 4/9-4/26 the Red Cross estimates 211,000 people were evacuated and 50 people were killed by damages Floodlist. Final April 2018 CHIRPS data is based on a relatively high number of stations in Kenya- more than normal- and CHIRPS estimates and stations are in general agreement, albeit in some areas CHIRPS is probably overestimating to some degree (see other entries below). CHIRPS data shows April rainfall was >100 mm above average in many areas of southern Ethiopia, southern Somalia, Kenya, Uganda, and Tanzania. Anomalies ~ 300mm are shown in some of the high elevation zones. The spatial pattern and size of anomalies are overall similar to those shown in ARC2 data.

Somalia SWALIM and Ethiopia NMA contributions to CHIRPS: SWALIM and Ethiopia NMS stations were highly influential for CHIRPS- reports in some areas of southern Somalia, southern Ethiopia, and eastern Kenya were ~100mm lower than CHIRP estimates. Result is that while CHIRPS shows above average precip across region, some of these areas anaomlies are weaker than otherwise would be based on satellite estimate (e.g. ~54 mm vs 180 mm)

China Stations were important for correcting CHIRP estimates in central-northern china and southeastern china. ~60 stations reported contrasting anomalies to CHIRP, with above average rainfall in central-northern china and below average rainfall in southeastern china. CHIRP showed below average across most of southern china. Could not find news reports to validate, but number of stations in agreement give support for CHIRPS accuracy.

Southeast Asia Stations were important for correcting CHIRP to above average rainfall in Thailand and northern area of Laos. ~25 stations show general agreement about this.

CHIRPS improvements During Rchecks on the first version of CHIRPS Final, it was identified that were substantially fewer stations than usual in east Africa and that CHIRP was overestimating rainfall in some areas. The combination of these factors gave concern that it might be reducing accuracy of CHIRPS data this month. Rcheckers and Pete Peterson, data curator, worked together to identify why so few stations were getting through (explained below). After these efforts, which resulted in a more stations being included and other positive outcomes, the final CHIRPS final is regarded with confidence. Including of a higher number of stations helped correct CHIRP overestimation in some areas e.g. coastal Kenya now shows ~150mm as opposed to ~300mm, which is more in line with stations, and Kilimanjaro shows values closer to ICPAC-blended data from bulletins. Positive outcomes of these efforts are better station coverage in east Africa in April 2018, identification of a screening step that needs to be evaluated more closely, and some of the added stations were in support of CHIRPS estimates, which is always great see. The reason for the initial lack of stations was identified- it was a data quality screening step (false-zero screening) that reduced 26 available GTS stations to 2. GSOD were reduced also such that Kenya only had 4 stations in CHIRPS. The hypothesis is that two factors in processing reduced number of days with reports to below the required threshold for them to be used for monthly totals. One factor was that there were no GTS reports on the GTS ftp site for one day (4/29), which counted against the monthly tally for the stations. Two, there may have been days where reports of 0mm were incorrectly identified as false, potentially b/c of extremely high CHIRP values. To get the stations back in Pete omitted the false zero screening step in east Africa countries. Screening steps are one of the processing features that will be revisited in the planned CHIRPS v3.0. In the meantime, an extra check may be introduced to processing prevent this type of problem.

Contributors: Laura Harrison, Will Turner, Marty Landsfeld

March 2018

East Africa: CHIRPS, CHIRP, and station reports show a convergent story-- anomalous wet conditions occurred in March across the region, with largest anomalies (>100 mm) in Uganda, Kenya, Burundi, Rwanda, and Tanzania. This led to major flooding problems in Uganda, Burundi, and Kenya.

Mediterranean: Stations included in CHIRPS reported the anomalous high rainfall that led to major flooding in northern Algeria, Gibraltar, Portugal and Spain from Storm Emma and Storm Felix, which was not previously represented in CHIRP.

Balkans: Stations also showed the high rainfall associated with Storm Emma that caused flooding in the Balkans. Contributors: Marty Landsfeld, Will Turner, Laura Harrison

Madagascar: CHIRPS, thanks to CHIRP and a couple stations) shows the heavy above average rainfall in northern Madagascar associated with Tropical Cyclone Eliakim that caused flooding and damages.

South America data Return of CHIRP data in southern Chile/Argentina. Satellite input had stopped contributing several years ago.

Contributors: Laura Harrison, Marty Landsfeld, Will Turner

February 2018

Southern Africa: Reversal of rainfall signal between January and February 2018 for a large region. This was noted during weekly FEWS NET Hazards monitoring, and CHIRPS data confirms. After an extremely dry January across large parts of southern Africa south of 10 S, extreme wet conditions were seen in February in Zambia, Zimbabwe, central-south Mozambique, northeast Botswana, and northern South Africa. As noted below, there were no stations reporting to CHIRPS in Zambia and Zimbabwe (fewer than normal were in Moz too). This wet signal is coming from several wet stations and CHIRP. Is also corroborated by other products (PERSIANNE-CCS, ARC2).

Tanzania: According to CHIRPS, a drier than normal February prevailed across Tanzania, with large negative anomalies (< -100 mm) in southern Morogoro province (also in northern Mozambique). This is consistent with CHIRP, ARC2, and PERSIANNE. After noticing that there was a station in southern coastal TZ that was being duplicated in CHIRPS, Rcheckers recommended removal of this station to prevent the duplication from artificially enhancing the dry signal (the duplication is a known problem in current processing method and is schedule to be fixed in next version). This station was not removed during processing of CHIRPS-final, so unfortunately it may be having a negative impact on the CHIRPS data by artificially enhancing dryness in the locale of Mtwara (TZ) and northeast Cabo Delgado (MZ).

Kenya: Station in east central Kenya removed. This station, at 52mm, was wetter than would be expected, given that a station next to it had ~5mm. To assess, we looked to IGAD/ICPAC dekadal bulletins for February. For their data they improve CHIRP data by blending it with many stations provided by some GHA countries. IGAD dekadal bulletins reported all three dekads had < 5mm each in that area. Thus the GHCN-v2 station was deemed inaccurate and removed. Note that this station does not consistently report and when it does it usually shows substantially higher rainfall than its GTS neighbor. The IGAD/ICPAC website was added to the 'Helpful Links' list so that all Rcheckers can quickly access the website for future checks.

Zimbabwe: No stations reporting again. Like in January 2018, no station reports went into CHIRPS. GTS stations did share reports for some stations but only for ~18 days. This was not enough to meet the requirement to go into CHIRPS (27 days) to make a monthly total.

Zambia: No SASSCAL stations reporting. This was concerning, as we typically receive ~10 stations and incorporate these into CHIRPS. According to the SASSCAL website (http://www.sasscalobservationnet.org/), these stations have not reported to them in around a month.

Artifacts in CHIRPS: Arcs and blockiness are visible in data, anom, z-scores in south-central to south-eastern areas of Africa. This was seen during Rchecks; Rcheckers notified CHIRPS data curator. Same artifacts came though in final version of product too.

Example of Rchecks: Here is an example of the type of process that occurs during CHIRPS Reality Checks. Compared to CHIRP, several stations created rainfall in southern Burkina Faso and Ghana. CHIRPS shows it as wetter than average for Feb 2018. One of the stations (GSOD, 277149) is especially high at 93 mm. This station we have not seen in CHIRPS in past year... so is suspicious. However, ARC2 also shows a signal of above normal rainfall, so suggest to not remove any of these stations.

South America: CHIRPS shows an anomalous pattern of dry-wet-dry for the areas around southern Columbia (dry), northern-central Brazil (wet), and southern Brazil/Uruguay/Argentina (dry). Some of the anomalous dryness was due to enhancement of CHIRP signal by stations. Each of these regions had >25 stations with convergent reports, expect for southern columia which had the extreme dry coming from ~15 stations. Persianne data also shows this pattern of anomalous dry-wet-dry. INMET brazil site also shows high > 250mm rainfall in same area as CHIRPS (http://www.inmet.gov.br/portal/index.php?r=tempo2/mapasPrecipitacao). Overall, the pattern and station reports appear robust.

Western Australia: As a result of Cyclone Kelvin, CHIRPS station data was much higher than CHIRP estimates, especially across the central and southern regions of Western Australia.

Contributors: Laura Harrison, Libby White, Marty Landsfeld

January 2018

Overview: There are no wiki entries this month. However, a full Rchecks was done on the January 2018 data. 14 stations were identified as problem data. All 14 recommendations were taken-- these stations were removed from the final version of January CHIRPS. For more information, we point you to the January 2018 section of the CHIRPSv2 station watchlist, which has comments and group discussions from the Rchecks.

Contributors: Laura Harrison, Sari Blakeley, Will Turner, Marty Landsfeld

December 2017

Southern Africa dryness in December 2017: As the dryness is shown across large area of southern Africa, comparison of z-scores from CHIRP vs CHIRPS is helpful for gauging extremity of situation. In CHIRP, Dec rainfall was around -0.5 standard deviation in parts of Botswana, all of Zimbabwe, southern Zambia, central and southern Mozambique, northern and southern South Africa, and parts of Namibia; in CHIRPS the pattern is more defined spatially, with December dryness being more focused and intense (z of -1 to -2) in parts of the area covering central/southern Botswana, northern SA, to central/eastern Zimbabwe and western areas of Mozambique. Also parts of Namibia and southern South Africa. Anomalies show below average Dec rainfall across most areas of southern Africa south of 15S. Exception is in an area in eastern South Africa. Something to also note is that there is quite good station coverage in Namibia (~40) and South Africa (~50)

East Africa dryness in December 2017: Below average Dec rainfall in Uganda, Kenya, northern Tanzania, much of Ethiopia and Somalia according to both CHIRP and from stations (CHIRPS).

Ethiopia: A note on the relatively large number of stations that report to CHIRPS in Ethiopia, which is typically undersampled in global precipitation data sets. There are consistently around 30 stations in Ethiopia in Dec (and November, October), thanks to contributions from Ethiopia NMA. Really nice to see this amount of measured rainfall coming into CHIRPS. Note that these are all 0mm in December, as expected based on climatology, but that in previous months there was more variability.

Southern Mozambique: December CHIRPS shows below average rainfall in central and southern MZ, with average anomalies aorund 75mm. This follows a below average November in southern MZ.

Central Kenya: Two instances of station duplication resulted in removal of the stations. One was near Mt. Kenya (triple counted) and one was to south (2x counted). The latter was removed because it had a moderate-large z-score (~ -2.6) and we did not want this to have more influence on regional CHIRPS than other stations, which also showed below average December 2017 rainfall but to a lessor magnitude.

Zimbabwe: 0 stations reporting; normally we have 5-15 GTS and GSOD. CHIRPS shows anomalies of 125-150mm in central and eastern areas of the country and below average by 10-50mm for most other areas of the country. Compared to CHIRP, CHIRPS anomalies are amplified by approx 10-30mm in most areas, and in some areas of central eastern areas with large anomalies, by 50-60mm. Given that there are no stations in Zimbabwe contributing to these estimates, this amplification is due to station(s) in other countries. CHIRPS estimates in Zimbabwe should be considered uncertain for this reason.

Brazil: Several stations in the western portion of Brazil's Amazon rainforest and the northern portion of Bolivia identified an anomalously wet December that was not represented in CHIRP. The station values were congruent with each other, and the resulting wet patterns in CHIRPS are congruent with patterns seen in December PERSIANN data (made available by CHRS, http://chrsdata.eng.uci.edu/).

Europe: All of Spain (except for the Northern coast) showed below average rainfall in CHIRPS for December, continuing a dry trend from the months before. Northeastern Italy has a station reporting surprisingly low values (added to station watchlist - #201424).

North America: The Pacific Coast - from the top of CHIRPS (Vancouver island) stretching down to the California Bay Area, and then inland along the Sierra Nevadas, down to Sequoia National Park - shows extremely dry conditions in CHIRP, the stations, and CHIRPS. December was a particularly dry month, with many stations reporting 0mm of rainfall, following from a relatively normal November and dry October. The stations pick up very dry conditions along the Central Coast (in Santa Barbara and then stretching to LA, San Diego, and to the Inland Empire). Several surprising blotches of high rainfall values in New Hampshire and West Virginia present only in the r-checks file (@ -79.8, 38.7 & @-71.1,44.4)

CHIRPS algorithm issues to explore and fix: Issue of station duplication was explored in more depth. Analysis showed that throughout the CHIRPS time series (back to 1981) there are typically 300 to 1400 stations that are included in CHIRPS more than once in a given month. This reoccurs in some known areas, like Kenya and southern Brazil, but analysis showed that it also occurs in areas of the African Sahel, eastern South America, the US, Australia, southern Africa, and elsewhere. Many instances were not visible in Rchecks because of location overlap. Steps to stop this duplication were discussed more, and consensus was that it would require an algorithm correction and reprocessing of CHIRPS to a newer version 2.1. Other improvements could also be implemented. More discussion will continue.

Contributors: Laura Harrison, Emily Williams, Will Turner, Marty Landsfeld, Libby White

November 2017

Northeastern Kenya/Southern Somalia: Very high amounts of rainfall occurred in early November 2017 in some parts of this region, as reported by FAO SWALIM stations. CHIRP also shows above average conditions in NE Kenya and across the northern parts of southern Somalia, though CHIRP anomalies are much smaller (up to 35 mm above average). Two Bay region (Somalia) stations reported around 400 mm rainfall, and that most of it came between Nov 1 and Nov 12. Nearby SWALIM stations reported much lower amounts ranging from 65mm to 185mm. Support for anomalous wet rainfall in that area also comes from ARC2, which shows positive anomalies for most of southern Somalia. Several important points are: 1) These storms do not seem to have affected southern areas of eastern Kenya and southern Somalia, 2) Despite the storms in some areas, products indicate below average rainfall for the October to December period for much of eastern Kenya and southern Somalia CHIRPS prelim ARC2, 3) For agriculture, the below average October and below average conditions after these early November storms are concerning. It should also be noted that the CHIRPS reality check process was especially useful in this case. Those two Bay stations interacted with the CHIRPS algorithm to produce an artificially widespread area of highly above average rainfall across the region. Discussions and experimentation yielded a solution. These stations were not included in CHIRPS, though other wet SWALIM stations were, and the extent of the anomalous rainfall became smaller. By not including these extreme stations in November 2017 data, CHIRPS is able to portray a more accurate pattern at the regional scale.

Stats

New CHIRPS - CHIRP high for all of Africa. This is may be plausable since areas of Somalia, Madagascar, S. Africa, Kenya and Gabon were increased by the stations observations.

New CHIRPS - CHIRP low for all of the Great Lakes region. This looks reasonable since many stations in Wisconsin lowered the values for the CHIRPS product.

CHIRPS algorithm issues to explore and fix:

1) Perhaps interpolation oddness to correct in V3. On the east coast of South Africa there are 4 stations on the coast showing high rainfall (~260) whereas CHIRP says ~120. Because there are no stations in the ocean to bolster the coastal ones the inland stations dominate and the high stn values essentially aren't being used. CHIRPS with these stations overlaid

2) See influence of extreme stations in top entry. Could be that larger impacts are in cases where a) stations are added in 2nd step e.g. SWALIM vs. anchor stations, which are included in 1st step, b) stations are in drier areas with larger decorrelation distance or deviations from average are very pronounced, c) other. Should be looked into more for V3. Note that initially, anomalously wet double-counted stations on Mt. Kenya were thought to be the main cause, but removing these had nearly no impact on the data.

Perth, Australia: There is a thick cluster of stations in Perth (fGTS amd fGSOD), some of which may be double counted or overlapping.

Andaman Islands: There is widely varying pixel values over this area due to the influence of the CHPclim. There is only one station on the Andaman Islands.

Contributors: Africa: Marty Landsfeld, Will Turner, Laura Harrison; Europe, India: Will Turner; East Asia and Oceania: Libby White; Middle East: Marty Landsfeld; South America: Seth Peterson

October 2017

Current East Africa IPC Acute Food Insecurity Phase Level 3 & 4 (Crisis & Emergency) areas http://www.fews.net/: October rainfall was below average and led to late start of the OND 2017 season by 10 to up to 30 days in some areas of southern Somalia. Some of these areas have experienced multiple back to back below average major rainfall seasons in 2016-2017.

Kenya: In northwest Kenya CHIRPS shows a large area of near zero values. In reality, substantial rainfall occurred her in October (and station report shows supports this). The reason CHIRPS does not show this rainfall is the estimates are a deviation from climatology in the CHIRPS algorithm, and teh climatology is near zero. Next version of CHIRPS will improve this aspect of algorithm so that extreme wet events are better captured.

Panama: Along the southern coast of Panama, CHIRP and RCHECKs shows wetter than average conditions; however, the CHIRPS prelim show it as drier than average. May be being forced by stations in Columbia or further north.

Contributors: Africa: Marty Landsfeld, Will Turner, Laura Harrison; East Asia and Oceania: Libby White; Caribbean, North & Central America, Europe: Emily Williams; Middle East: Laura Harrison; and South America: Seth Peterson

September 2017

Current East Africa IPC Acute Food Insecurity Phase Level 3 & 4 (Crisis & Emergency) areas http://www.fews.net/: September rainfall was mildly below average by 10-20 mm in some of these areas in Ethiopia (southern Oromia and central Somali), Somalia (Bakool in north part of southern Somalia), and Kenya (coastal zone). Rainfall in the next 1-2 months is most important to the current season in these IPC Phase 3+ areas, but average to below average September rainfall is not a good start. Some of these areas have experienced multiple back to back below average major rainfall seasons in 2016-2017.

Nigeria: There is a rather large disparity between CHIRPS and ARC2 in Nigeria for the month of September - CHIRPS is relatively wet in central/northern Nigeria, and relatively dry in the southern portion of the country; ARC2 shows nearly opposite anomalies in the same regions, with a large wet anomaly in far south/coastal area. RFE2 anomalies in Nigeria are similar to CHIRPS. Floodlist (http://floodlist.com/africa/nigeria-floods-kogi-september-2017) reports considerable flooding in central Nigeria, supporting the anomaly values from CHIRPS. Floodwaters from the Niger and Benue Rivers put downstream cities at risk (Sarkin Noma, Lokoja and Ibaji in Kogi State).

East Africa: Across a large area of continental eastern Africa June to September rainfall accumulations were above average. This includes southern Chad, Sudan, South Sudan, Uganda, Ethiopia, and western Kenya. In some Ethiopia and Kenya highland areas the June to September totals were around 2.5 standard deviations above normal. Above average rainfall in September contributed to these seasonal wet anomalies in parts of all these countries.

West Africa: For a large area of West Africa, CHRPS shows September rainfall was below average. This occurred in Ghana, Togo, Benin, Senegal, southern Mali, eastern Guinea, Burkina Faso, Niger, northern and southern Nigeria. According to CHIRPS, it was a continuation of dryness that also occurred in August in some of those areas (eastern Guinea, southern Mali, parts of Burkina Faso, Niger, and northwest Nigeria). Burkina Faso and eastern Guinea also had a drier than average July.

Australia: Two stations were removed, one in Victoria and the other in Queensland. There were also several climatology artifacts across Australia.

Fiji: One station was removed as it was much, much lower (4mm) than CHIRP climatology showed. Station did not impact CHIRPS much.

Philippines: Station values are in agreement in CHIRPS, but show higher precipitation (sometimes upwards of 1,000mm as opposed to 500mm) than in CHIRP. The ~20 stations in the Philippines greatly influenced CHIRPS.

Taiwan: Station values are in agreement across the island, show significantly lower values than in CHIRP. However, we only have station data for the lower elevations, and most of the precipitation shown in CHIRP is in the higher elevations.

Japan: Station values in agreement but show less precipitation than in CHIRP. The station values seem to have had a high impact this month.

North & South Korea: There is a sharp contrast between the CHIRP (higher than average precipitation) and the CHIRPS (lower than average precipitation). Stations appear to be in agreement with each other, so values were kept.

Spain and Portugal: CHIRPS shows September rainfall was below average across both countries, which continued a severe drought in some areas. More recently, massive wildfires in northern Portugal and northwest Spain have consumed forests and killed at least 39 people.

France: Northern France (in the Cotentin Peninsula, in the Caen region) has a noticeable artifact. This artifact is present for all months in CHIPClim.

Croatia: The coastal part of Croatia had a large positive rainfall anomaly that is captured in CHIRP, but is intensified with the rain gauges in the region.

CHIRPS algorithm issues to explore and fix: Rchecks efforts identified 18 stations to be removed from the pre-final version of CHIRPS. Some of these were stations with what appeared to be possible bad values, and the values were applied to two or three locations. This procedure of allowing a station value to be used in more than one location needs to be corrected (stopped). It is especially problematic in areas with low station density.

Contributors: Africa: Laura Harrison, Will Turner, Emily Williams; East Asia and Oceania: Libby White; Europe and Middle East; Sari Blakeley; Caribbean, Central, and South America: Marty Landsfeld; North America: Laura Harrison

August 2017

Ethiopia: In northern Ethiopia, data shows a swath of above average rainfall. No stations reporting there. Anomaly values agree with ARC2: 125-200mm above average. Between CHIRPS and ARC2 there are differences in spatial extent of wet anomalies- CHIRPS has them focused on north-central areas, ARC2 has them across northwestern areas. Overall JJA CHIRPS anom is above average because of anomalous August rainfall. Rainfall in late July and August is important for seasonal totals; June-July were deficit months.

Coastal West Africa: Above average August precipitation; consistent with reports of flooding in Guinea/Sierra Leone (Africa hazards report: (ftp://ftp.cpc.ncep.noaa.gov/fews/threats/afrhaz20170831.pdf)

Côte d'Ivoire: A station in southern Ivory Coast was put on the watchlist for having a much higher value than both nearby stations and CHIRP (333mm vs. ~160mm).

Nigeria: Three Kukua stations were drastically lower than CHIRP and surrounding stations (~16mm vs. ~200mm). These stations were removed.

Tanzania: Data show above average rainfall in some areas of northeastern Tanzania including along coast and islands. Based on 4 stations and CHIRP to a minor extent.

DR Congo: Data shows strange blob of below average rainfall in east Congo. Possible from a weak below average signal in CHIRP; maybe from additional influence of moderate below avg stations in Rwanda/Burundi?

Southern Mexico, Guatemala, Belize: CHIRPS shows below average rainfall in these areas; based on ~50 stations in Mexico, several stations to the south of Guatemala, and to a lessor extent CHIRP. 0 stations in Guatemala and Belize contribute reports to CHIRPS.

Australia: The south eastern Australian coast is somewhat dryer according to station data when compared with CHIRP.

Indonesia: Northwestern Papua had a station removed because it was showing inconsistently lower rainfall than CHIRP and the surrounding stations.

Brunei: A station just outside Brunei was provisionally removed because it reported over 1,000mm of rain vs. ~400mm in CHIRP and surrounding stations.

China/the Koreas: Hubei, Anhui, Jinlin, and most of both North and South Korea station data reported heavier rainfall than CHIRP. Hubei and Anhui stations reported twice as much and Jinlin and the Koreas reported roughly half again as much as CHIRP.

Hurricane Harvey: CHIRPS shows the extreme rainfall associated with Hurricane Harvey in Texas, Louisiana, Oklahoma, and Arkansas. Stations increased the above average signal in CHIRP. CHIRPS anomalies are +300mm for large areas.

CHIRPS algorithm issues to explore and fix: 1) Double-counting stations 2) SETH'S MYSTERY. 1) Currently, when a report from a station is not available, the algorithm looks to a neighboring station to fill it. This can result in the same station value being counted two or more times. This method can cause large problems when double-counted values are bad values; in less extreme cases is still hard to assess what data is right or wrong. Overall, there should be a catch implemented to prevent double-counting. 2) SETH"S DESCRIPTION : in coastal central Brazil, near the town of Salvador, CHIRP shows relatively low rainfall, all of the nearby stations also show low rainfall, somehow RCHECKS/CHIRPS showed a massive increase in rainfall 180 to 373mm, 101 to 219mm are two examples.

Contributors: Laura Harrison, Africa & North & Central America; Libby White, Africa & East Asia and Oceania; Will Turner, Africa & Eurasia; Seth Peterson, South America

July 2017

Ethiopia: Below normal rainfall in July 2017 in north eastern Ethiopia. A consistent story across data products (CHIRPS, CHIRPS and stations, ARC2, PERSIANNE, NMA mid-season assessment)

Sudan: V artifact in Sudan (from CHIRP)

Japan: Hokkaido stations report slightly dryer conditions than indicated in CHIRP.

Australia: There is a strange square artifact in New South Wales.

Central America: Above average July rainfall in eastern Honduras, eastern Nicaragua, northern Costa Rica, Panama. Below average in western areas, southern Mexico, Guatemala, Belize, some coastal areas of Mexico (Pacific and Gulf). Overall agreement with PERSIANNE data in terms of this pattern of anomalous rainfall. There are gaps in station reports in Central America this month. Guatemala has 0 stations. Same for June 2017. In May and earlier in 2017 typically had 2 or more (GTS & GSOD). Honduras, Costa Rica, 0 stations. Panama, 3 GTS. Honduras typically has 2 GHCN-v2, Costa Rica has 2 (GTS and GSOD).

Southern Mexico/Guatemala central border area and Belize: Circular below average features. Coming from CHPclim, which has higher climatology in those areas (% of normal applied to higher values translates into larger anomalies). No stations in these areas to compare to.

Northern US and British Columbia: In western areas, CHIRPS shows a swath of below average rainfall for July (1 to 2 standard deviations below normal). Similar area as recent wildfires. Anomalies are average in most of Western US (no rain), with exception of Arizona (and NW mexico) with above average by 25-75mm. Above average rainfall in SE Colorado, SE Oklahoma, and regions near Lake Michigan and Lake Erie including Ohio, Indiana and southern Wisconsin. Also above average in mid Atlantic seaboard. Below average mixed with average in much of SE US, southern Texas, and central US.

CHIRP issues in Indian Ocean: Artifact in CHIRP climatology in July—mottled rainfall pattern across southern Indian Ocean including Madagascar area. June also has a (different) mottled pattern in CHIRP climatology. This needs to be addressed before offering CHIRPS data or CHIRP-based data products over ocean.

Contributors: Laura Harrison, Africa & North & Central America; Marty Landsfeld, South America and regional stats; Libby White, East Asia and Oceania; Sari Blakeley, Africa & Eurasia; Will Turner, Africa

June 2017

Ethiopia: Inclusion of stations enhanced the magnitude of June rainfall anomalies in some areas, compared to satellite-based estimates from CHIRP. Across Oromia and central Ethiopia anomalies increased from ~ -20 mm (in CHIRP) to ~-50 to -70 mm (in CHIRPS). In northwestern highlands area, including the stations led to the extension of anomalously wet conditions from east Sudan into and across the NW highlands of Ethiopia.

West Africa: CHIRPS shows there was a good start to the JJAS rainfall season, based anomalously wet conditions in the June data. In regard to the positive rainfall anomalies, stations and satellite-based estimate (CHIRP) were in general agreement across Gulf of Guinea region; stations added information in Senegal, Burkina Faso, and Niger.

Senegal In Senegal, there was evidence of high rainfall in the interior (near Tambacounda) through ANACIM’s rainfall page (http://www.anacim.sn/ and http://www.anacim.sn/meteorologie/produits-du-gtp/).

Madagascar: Madagascar has some very high rainfall amounts along the eastern coast. There is elevated rainfall along this zone in the CHPclim, and two stations nearby with high rainfall amounts probably contributed to the overall high rainfall along the eastern coast. To note- this data should be used with caution.

Georgia (country): Very high rainfall has occurred in southern Russia along the border with Georgia. There are news articles supporting above average rainfall in Georgia here (http://www.bbc.com/news/world-europe-33125879).

Central Kalimantan, Indonesia: Oddly low station (150.8 mm) among higher satellite and other station readings (~200-400 mm), but could be due to Geography. Station was put on watchlist but not removed from CHIRPS.

Jakarta, Indonesia: Values in CHIRPS much higher than CHIRP - station itself did not seem to have unreasonable values, but because it was counted twice it seemed to be influencing the calculations to an unreasonable degree. The station was removed.

10 stations removed, 15 added to watchlist Also, the need for an improvement in the CHIRPS algorithm was highlighted by a case in Rwanda where a station report was double-counted (and that station happened to have a bad value). Station was removed and issues was noted with data curator.

Contributors: Laura Harrison, Africa & North & Central America; Marty Landsfeld, South America and regional stats; Libby White, East Asia and Oceania; Sari Blakeley, Africa & Eurasia; Will Turner, Africa

May 2017

SouthEast Asia: Thailand, Cambodia, Southern Vietnam and Southern Laos as well as Sumatra and Indonesia are wetter than usual by 100 mm or more. Northern Vietnam, Taiwan, West Coast of Myanmar and the Chinese provinces of GuangDong, Fujian and Jiangxi are dryer than usual by 100 mm or more.

Australia:

Southern coastal Angola: SASCAL stations report above average rainfall, with totals of 20-60mm.

Tanzania: As part of an above average rainfall signal along coastal TZ and SE Kenya in May 2017, a GTS station in Zanibar reports 638 mm. In terms of standardized anomaly at a station (z-score of 3.2), this is one of most extreme reports of global stations. Something also to note is that there are some extremely large values in CHIRPS (>1000 mm) in this area. CHIRPS anomalies are mainly 200-300 mm above average, but there are a few pixels with anomalies 500-900 mm. They are a product of the algorithm, as CHIRP rainfall totals are around 600-800 mm and anomalies are 300-400 mm.

East Africa, Lake Victoria area: High rainfall values- from 200-460 mm reported by 4 stations. Several others nearby also report positive anomalies.

Niger, Chad, Sudan: Data artifacts in northern parts of country. These are from the CHIRPS climatology, CHPclim. New TAMSAT v3 data also has them because they also use CHPclim as their climatology. Artifacts previously noted in this wiki. Needs attention in next version of CHIRPS/CHPclim.

Kenya: A bad station value at a GCHN-v2 station in Garissa was identified and removed from CHIRPS. It was identified using a report of MAM 2017 rainfall from the Kenyan Met Agency. A neighboring GTS station reported 13 mm, which is more realistic.

Argentina: Above average rainfall in NE (see Brazil entry). In western part of Argentina CHIRPS data has a visible north-south artifact line.

Brazil: In southern Brazil and NE Argentina CHIRPS is correctly showing an area with concentrated high rainfall values. This is based on comparison to Argentina Met Agency maps. In northern Brazil and eastern Columbia, CHIRPS shows a widespread below average rainfall signal. This comes from ~11 stations and in part of the anomalous area, CHIRP. Circular data artifacts are seen in southern Brazil. These artifacts were previously noted in this wiki. Needs attention in next version of CHIRPS.

N. America: Stations had a large effects in the midwest and eastern seaboard. CHIRP did not do well in these regions but the station adjustments corrected that.

Italy removed a false zero in south central region.

Regional Statistics checks The Africa region contained a new high for the maximum value in the region of 1716.9 on the island of Zanzibar. Globally, a new high for the maximum value of nearly 2400 was detected near Chichi-jima Island south of Japan.

March 2017

Madagascar: Northern Madagascar has highly above average rainfall in March CHIRPS, with anomalies on the order of 200 mm to 500 mm and March totals up to 900 mm (35"). This information comes from stations and the satellite-based CHIRP. In the first week of March a strong tropical cyclone named Enawo made landfall in northern Madagascar. Enawo is the strongest cyclone to make landfall in Madagascar in 13 years. It was equivalent to a Category 4 hurricane. 20,000 homes were destroyed.

Angola: CHIRPS shows below average rainfall for large area in central western Angola. This information is coming from one station (which has a reasonable rain value) and also CHIRP. The satellite-based products ARC2 and CHIRP both show below average rainfall in that area. According to CHPclim this area typically gets 200-250 mm in March (ARC2 shows 150-200 mm in its climatology). The station and CHIRPS report 100-130 mm in the area. Persistent dryness has been an outgoing issue in this part of Angola for the October to May season, with suppressed rainfall since December.

East Africa: CHIRPS shows below normal rainfall across much of this region: In Kenya, northern Tanzania, southern Somalia, and southern Ethiopia. This indicates a poor start to the March to May rainy season. The negative anomalies are supported by 40+ stations (many of these are in Somalia), by CHIRP, and also by ARC2. Concern for the season due to the poor start is detailed in the CHC blog.

Northern Somalia: An area with one station reporting 41 mm rain that is near stations reporting 0 mm rain was examined. Support for the idea that this mix actually occurred came CHIRP and RFE2, which showed that satellites also picked up on some rainfall there. Should be noted that CHPclim shows this area is typically wetter than surroundings.

Honduras: An area of northeastern Honduras, near San Pedro Sula, has three GSOD stations that report above average rainfall. One of those has a very high rain total of 411 mm, another reports 206 mm. Together, and with input from CHIRP, they are responsible for above average rainfall in CHIRPS in this area. The anomaly at the very wet station was ~300mm. Given such a large magnitude wet anomaly, and convergence from these stations, we expected to find support for a wet event in other data sources. CHIRP shows a small wet anomaly. Otherwise, no support comes from PERSIANN or CMORPH rainfall products. No news reports were found online. These stations seem to report on a semi-monthly basis, rather than monthly, and tend to report high rainfall values. We retained these stations in CHIRPS, but added them to the watchlist for future review.

Australia: Despite [record breaking rainfall in March http://www.news.com.au/technology/environment/the-wettest-march-in-recent-history-is-on-the-cards-as-sydney-clocks-up-16-rainy-days-and-more-than-a-week-to-go/news-story/988409de59d01a92197439139509d007], including a particularly intense [cyclone https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/03/28/cyclone-debbie-roars-ashore-in-australia-with-160-mph-wind-gusts-and-30-inches-of-rain/?utm_term=.0603b199256a], there were a few very low/zero value stations that we tossed out.

China: Heilongjian and Altay China had several stations that were showing unfeasible high values (300mm+) in relatively dry regions. No evidence of localized weather events could be found to support them, so they were tossed out. Similarly, Jiangxi had some suspiciously low values (~40mm), especially when viewed in anomaly, so they were tossed out as well.

Argentina contained two stations that were outliers, compared to their neighbors, and were removed. One GSOD station had a z-score of 5.28.

South America had the highest mean CHIRPS value for March in our records. The CHIRPS Mean regional statistics shows the highest mean value on record and by far the highest Maximum CHIRPS value on record. We investigated these values and found the there were record rains reported along the Peru/Ecuador border by The Atlantic and Earth Chronicles websites.

19 stations removed, 25 added to watchlist 19 stations were removed from the preliminary version of CHIRPS due to being identified as unrealistic values during the Rchecks process.

Contributors: Laura Harrison, Africa, Central America; Marty Landsfeld, North, South & Central America; Libby White, East Asia and Oceania; Sari Blakeley Africa & Eurasia

February 2017

South Africa Two very wet stations in northeast (near 24.5S, 30E) attracted our attention. The wetter was more than 350mm above average with a value of ~ 550mm. These are on the eastern edge of mountain range. Conditions were wetter than normal across the region. Due to these factors, the station values were deemed ok and retained in CHIRPS. If these station are indeed accurate, they are valuable to have in CHIRPS because captures the impact of orographic rainfall enhancement in the region. Will keep an eye on them going forward.

Tanzania A GHCN station in Tabora (central TZ) was removed. It reported ~15mm and seemed to be responsible for surrounding negative anomalies in CHIRPS. In comparison, CHIRP doesn’t show a negative anomaly- it shows near average in the area; RFE2 shows above average. ARC2 daily time series shows rain for many days in February (~100mm total).

Northern Mozambique Large negative anomalies. Station and CHIRP in agreement. Drought has affected this region for most of the past several months [1].

Australia Very wet February in western Australia. Stations and CHIRP show the extreme conditions. In Perth, Feb 2017 was the wettest in decades at many sites. According to Australia's BoM: Monthly rainfall totals were in the 80-140 mm range across Perth, and were more than five times higher than normal. Perth Metro's monthly total was the second-highest February rainfall total on record at the site and the wettest for 62 years, since the record high of 166.3 mm in February 1955.

California, USA CHIRPS shows the extreme rainfall that helped to end the drought for a majority of California [2]. Atmospheric river events in February brought flooding, landslides, and damaging winds.

Contributors: Laura Harrison, Africa, North America, East Asia and Oceania; Marty Landsfeld, Africa, South & Central America; Sari Blakeley Africa & Eurasia

January 2017

Southern-Eastern Africa rainfall dipole continues January CHIRPS shows the anomalous wet (dry) conditions in southern (eastern) Africa that persisted since November. The dipole was most prevalent in December and January. January CHIRPS shows rainfall 150mm+ above average in Botswana, South Africa, southern Malawi, Zimbabwe, and Mozambique, with the largest anomalies (250mm-400mm) in eastern Zimbabwe/central Mozambique. Deadly flooding occurred in Limpopo and Mpumalanga (South Africa) [3]. CHIRPS shows northern Mozambique and Madagascar with January totals that are 100-250mm below average. Rainfall was more than 2.5 standard deviations from the norm in some of these areas. In Tanzania rains were 50-75mm below average across much of the country.

Kenya Rchecks identified three stations that reported questionable values in western and southern Kenya, and these were not included in CHIRPS final. Two appeared to be false zeros, and one appeared to have an erroneous high value that would have influenced data near Nairobi and over Mt. Kilimanjaro in Tanzania.

Ethiopia Many near-zero value stations earned a closer look. They seemed reasonable given January is a relatively dry month in most areas. In SW Ethiopia, where there typically is rain, CHIRPS and stations showed agreement with CHIRP and RFE2 about the area being below average by ~20mm in SNNPR.

Western Sahara On the coast of Western Sahara there are several artifacts that must be a part of CHPCLIM.

Thailand Southern Thailand's extreme wet January rainfall was one of the most extreme locations globally in the CHIRPS domain (50S to 50N). Five Thailand stations had rain reports that were more than 2.7 standard deviations from the norm. These stations measured 500mm-800mm (~20"-30") rainfall. CHIRPS shows that some areas received 500mm above average rains. Extreme values in CHIRPS are corroborated by NASA GPM data [4]. In mid January, 43 people had been killed and 1.6 million people were affected [5].

Pakistan Unusually high rainfall amounts in Pakistan were observed in January, in line with reporting of floods and high snowfall in the mountains.The Pakistan government has requested aid from the Pakistan Red Crescent Society. http://reliefweb.int/disaster/fl-2017-000017-pak

California, USA CHIRPS shows above average rainfall across the state, with wettest anomalies in the northern Coast Ranges and Sierra Nevada mountains. Much was attributed to [6] a series of atmospheric river storm systems [7]. The wettest station along the central coast was in Big Sur, which received 19" rain, as was forecast [8].

Queensland, Australia One zero value CHCNd station surrounded by higher value stations was tossed out.

Taiwan One zero value fGSOD station among stations reporting higher values was tossed out.

21 stations removed, 30 to watchlist Rchecks examination identified these stations as having values that were not accurate, based on careful comparison to other data, neighbor stations, and to reports. Past reports from these stations were also incorporated in decisions. See the watchlist for more details. [9]

Contributors: Laura Harrison, Africa, North & Central America; Marty Landsfeld, Africa, North, South & Central America; Libby White, East Asia and Oceania; Sari Blakeley Africa & Eurasia

December 2016

Tanzania, northern Mozambique, northern Zambia, Madagascar, southern Kenya and Uganda: CHIRPS shows drier than normal conditions across this large region. Largest deficits are 100-150 mm. The CHIRPS anomalies come from reports by approximately 20 stations and also from the CHIRP satellite signal. Central/southern Tanzania and northern Mozambique were the epicenter of deficits according to CHIRP. The combined influence of stations and satellite resulted in December rainfall estimates that are 1.5 to 2 standard deviations below average across the region.

Zimbabwe, east Botswana, southern Mozambique, northeast South Africa: Above average rainfall in these areas. Multiple products (CHIRPS, ARC2, TAMSAT, CHIRP) are in agreement about this dipole pattern of rainfall [10]. Stations in Zimbabwe and South Africa were especially scrutinized because of high variability. Several stations in this region, and the Kenya/Tanzania/Zambia region, were removed due to extreme values. See our station watchlist for more information.

Ethiopia: A GHCN-v2 station that reported extreme wet value was removed (36.8E, 7.7N)

Nigeria: Removed station with strange value at a station (=110204); an error from new station source (Kukua) that made it past pre processing.

Nicaragua, Honduras: Large wet anomaly along eastern coast, with CHIRPS showing show areas recieved 650mm (200 mm above average). A feature from CHIRP, as there are no stations reporting in area. The PERSIANNE-CCS precipitation dataset also shows this wet feature.

Argentina: Three GCHN-v2 stations in different locations report the same value (267 mm). Curious and questionable. Added these to station watchlist to keep an eye on in future; based on previous months, there are no known issues at these stations.

Australia: A few stations with suspicious zero values were thrown out in Western Australia and Queensland.

Kochi, India: Suspicious zero value station was removed.

Various CHPclim artifacts: CHIRPS is being repeatedly affected by the following December CHPclim problems: Extreme value on Canary Island, striping in western Sahara, small wet area in Algeria near 1E, 29N creates strange symbol-like feature in CHIRPS. Also a large artifact in Egypt (a 1.5 degree radius splotch of low values).

Contributors: Laura Harrison, Africa & Central America; Marty Landsfeld, Africa, North, South & Central America; Libby White, East Asia and Oceania; Sari Blakeley Africa & Eurasia

November 2016

NW Argentina: Area is generally dry except for an area of high precipitation around the village of San Miguel de Tucuman. A newspaper report from November 7th notes that a soccer/futbol game was canceled because there was water on the field.[11]

Italy: In north-western Italy there is a wet anomaly, and then a dry anomaly to the east; various reports back this up [12] [13] [14]

Czech Republic: There is a dry anomaly in Ceske Budejovice, checks out according to sources [15]

Alanya, Turkey: Dry along southern coast [16]

Iran: The east tends to be dry, but there was a station that showed an increase in 14 cm of rain (small amount); this showed up as an extremely positive z-score.

India: Southern India (into Sri Lanka) is showing up as extrememly dry, which is correct and backed up by sources indicating the monsoon season has had few rain days and ran a large deficit by the end of the month [17] [18] [19][20]

Contributors: Emily Williams, Eurasia; Marty Landsfeld, North & Central America; Libby White, East Asia and Oceania

October 2016

Somalia and east African horn: CHIRPS and stations show expansive areas of below average rainfall in October. Areas of largest deficits are in southern Somalia (more than 100 mm below average) and central Kenya, near Meru (more than 200mm below average). The deficits are highly concerning in Somalia as the October is generally one of the wettest months of a very short cropping season.

Gabon: CHIRP and 3 stations in agreement about below average rainfall in western Gabon.

Sudan: No stations are reporting to CHIRPS in Sudan this month. The number of stations reporting in this country seem to oscillate between either 0 or around 10.

Southern India: CHIRPS shows deficits of 100-200 mm in southern India. The data correctly indicate widespread drought conditions, which have been reported to be negatively impacting water resources for agriculture and other uses. In Kerala state, "most of the water reservoirs across the state have recorded a water deficit of 50 per cent. The South West monsoon has been deficit by 34% while the North East monsoon is expected to be deficit by 69%." news report

Indonesia: Stations in the region are generally high value and backed up by weather reports; however, a few stations showed great variation with their neighbors, some over 300mm higher.

China: Several stations around Qinzhen and Shenzhen showed ~300mm higher values than their neighboring stations.

Yonaguni, Japan: One station shows a value ~250mm higher than its neighboring values.

Contributors: Marty Landsfeld, North and Central America and Africa; Libby White, Oceania and East Asia; Seth Peterson, South America and Africa; Sari Blakeley, Europe; Laura Harrison, Africa and Oceania

September 2016

New Zealand: the pattern in CHIRPs of North Island wet, South Island dry is correct [21]

Ethiopia: the pattern in CHIRPs of the SW part of the country being dry is correct [22]

Brazil: southern Brazil was indeed dry in September [23]

Contributors: Marty Landsfeld, Europe and West Asia; Seth Peterson, South America, Australia, NZ, & Africa; Sari Blakeley, North America & Africa

August 2016

Japan: A few stations were able to capture the heavy rains on Japan's east coast better than CHIRP alone (~400mm - 500mm as opposed to CHIRP's less than 200mm on average). [24] [25]

Shandong, China: Two stations reported nearly 500mm in rain, while surrounding stations and CHIRP report less than 200mm (on average). Weather reports do not indicate high levels of localized rain in that region.

Hainan, China: Typhoon Dianmu seems to be responsible for the very high (847.59mm) precipitation recorded, though CHIRP did not capture this rainfall as well (reported between ~200mm to ~500mm).

Contributors: Marty Landsfeld, Europe and West Asia; Libby White, Oceania & East Asia; Seth Peterson, South America & Africa; Sari Blakeley, North America & Africa

July 2016

Somalia: Many stations reported zero or near-zero values, while CHIRP estimated non-trivial values but it was decided that since CHIRP will over-estimate low values in these conditions that the station data probably was correct. Having viewed July estimates of ARC2, the decision was supported.

Madagascar: Discontinuous patterns of precipitation, especially anomaly and z-score values, were noted but Pete explained how this is part of the climatology and will hopefully be fixed in the next version of CHIRPS.

Multiple countries: 17 stations with suspect values were added to the watch list. It was determined that their effects were minimal so were not removed to create another version.

Central America: Good overall agreement with ARC2 product. It was noted that there are only 5 stations for all of Honduras, Nicaragua, El Salvador & Panama which unfortunately is typical.

Brazil: Many zero values new Sao Paulo/Rio area that generate "dimples" in the product but viewing precipitation map from INMET website confirmed dryness.

Mexico: Station data reduced CHIRP values south of Mexico City and near Santa Cruz.

China: Stations in Hubei, Shanghai, and Shanxi picked up on heavy rains not present in CHIRP [26] [27]

Time Series Statistics Plots: All regions within normal ranges with the exception of southern Africa which tied CHIRPS Maximum value. It was a very localized occurrence and accepted.

Contributors: Marty Landsfeld, North America and Africa; Libby White, Oceania & Asia; Seth Peterson, South America & Africa; Sari Blakeley, Europe & Africa

June 2016

Colombia: Colombia was generally drier before stations added, stations made it wetter. One station (20758) led to a z-score about -4.5 (value of 30mm, where surrounding area was 200-300mm), and was therefore temporarily removed.

Guyana: A station (205606) reported 1380.6mm of rain on the coast; while there were a couple of reports of flooding [28], none matched the magnitude of the station, and was therefore temporarily removed.

Brazil: Several stations (205639, 205664, 205655, 205651, 205645) all had values of over 1000mm in climatologically drier areas. All were removed. A station in SE Brazil (285717) had a high rainfall value in a climatologically wet area, creating a wet “bubble” in anomaly space, and was temporarily removed.

Southern Chile: Dry anomalies/z-scores, which match up with TRMM.

Costa Rica: A station in Costa Rica/Nicaragua shows a high positive anomaly, where CHIRP and TRMM shows negative. Weather Underground reports 242mm [29] , matching the CHIRP value but not the station value. Therefore is temporarily removed.

Mexico: Tropical storm Danielle caused flooding, shows up in CHIRPS well [30] ; Mexico City showed up with z-score of 4.34.

United States: In California and Nevada, the z-scores for CHIRP are high for slightly high anomalies, explained by their having very dry climatologies. In West Virginia heavy rain showed up in CHIRPS, backed up by national forest alert [31]

Indonesia: There was heavy rain on the island of Java, leading to flooding [32], as well as on Sulwesi. This matches with reports [33].

Taiwan: A station (203670) off the northern coast of the island reported 1440.40mm, while another station (203682) on the island reported 1383.09. Super Typhoon Nepartak came through in June, reportedly dumping 154 mm in one day [34] . TRMM reports high anomalies in the area (300-500mm extra) [35], but not nearly as high as the station values.

Oceania: New South Wales was hit with an intense storm system, ranging from Brisbane to Sydney and even reaching Tasmania. [36] [37]

Ethiopia: New stations! The addition this month is ~25 stations from Ethiopia’s National Meteorology Agency. The stations had particular influence on CHIRPS in the northern Oromia region. Here, CHIRP estimated below average rainfall but the station observations showed the deficiency was larger in magnitude—at three stations June anomalies were 116-130 mm below average. Across climatologically wet parts of Ethiopia, the final CHIRPS product shows N/S oriented swaths of above average rainfall along the Sudan border region, below average June rainfall along western highland areas (anomalies -30mm to -90 mm), and average to slightly above average June rainfall in eastern highlands areas.

Guinea/Sierra Leone: The GSOD station 276516 (Data=688.59 mm, CHPclim ~ 350 mm) at Conakry, Guinea was checked due to its large positive rainfall anomaly. It was deemed ok to retain in CHIRPS based on convergence with NOAA’s ARC2 data, which also shows above average rainfall in the Guinea and Sierra Leone area in June. Compared to ARC2, CHIRPS shows smaller magnitude anomalies, which range from 50-200mm. ARC2 shows 300-500mm anomalies.

Madagascar: Some visible block patterns in CHIRPS data. These are also seen in CHIRPS Prelim and CHIRP. Note that there is blockiness in CHIRPS data in many low rainfall areas in the general region, but these stand out in Madagascar because of some high rainfall values mixed in.

Europe: CHIRPS shows above average rainfall in June across large areas of western Europe, southern Europe (excluding Spain, Portugal), and parts of south eastern Europe (especially Romania). In some areas, based on the CHIRPS standardized anomalies (z-score maps), the magnitude of rain received in June 2016 classified as 1 in 7 year to 1 in 50 year events. Photos and descriptions of some of the damage can be seen here: [38]

China: Heavy rainfall and reports of flooding in southern and eastern China [39], plus the reports from >50 stations substantiate the above average rainfall shown in CHIRPS (100-200mm anomalies).

Japan. CHIRPS shows positive rainfall anomalies of 50-200mm in southern Japan. These are substantiated by ~30 stations and Floodlist reports of deadly floods and landslides. On June 21st for example, Kosa in Kumamoto prefecture received over 180 mm rain in two hours: [40]

**Due to Rchecks** 26 station reports were removed from the final June 2016 CHIRPS product. Please see the R Checks STATION WATCHLIST for more information (under Helpful Links)

Contributors: Emily Williams, Americas & some of Oceania; Libby White, Oceania; Laura Harrison, Africa Europe & Asia

May 2016

Columbia Comparing CHIRP and CHIRPS, CHIRPS has more negative anomalies on the western coast and positive anomalies on the eastern border. There is a station near the Panama/Columbia border with a low value which drives the area down, but it’s confirmed in a separate precipitation report [41].

Brazil There is a station in the Southeast with a very high value (1107.0) that is surrounded by low value stations. CHIRP shows low rainfall values for that area. The addition of the station led to a circular artifact in the area, and was subsequently removed. It was a GTS station, with seq-num of 205708.

There are two more stations in Southern Brazil also creating circular artifacts; however, their values are not high enough to warrant removal. They have been added to the watchlist (205722).

Central America It is very, very dry with a historical low maximum temperature, however, nothing looks out of place [42].

Liberia The CHIRP and CHIRPS products both show dry anomalies inland and wet anomalies along the coast; however RFE and ARC2 [43] show the opposite. After adding up precipitation values from a site (not verified for accuracy)[ http://www.accuweather.com/en/lr/monrovia/361788/may-weather/361788?monyr=5/1/2016&view=table], the values reached 84 mm, which backs up the ARC2 story. However, there were some flooding reports for Monrovia [44] [45]. Overall, it is unclear as to whether or not CHIRPS is right on this one so we should watch trends in Liberia in the future.

Contributors: Emily Williams, Liberia & Central & South America;

April 2016

Central America Dry along Eastern coast of Costa Rica and Panama. Station on S. coast of Panama shows anomalously high value but seems to match with TRMM [46]. Weather underground report says in April it got 4.59 inches, or 116 mm [47]. Didn’t have visual impact on CHIRPS so can leave it.

United States April was the record wettest in southern plains, and the record warmest in northwest; [48];CHIRPS shows this very clearly. Station near Wichita Falls, Texas was permanently thrown out as it showed a super dry anomaly in the middle of very wet anomalies, and has historically given anomalously low values [49]. Station near Jarbidge, Nevada reported a high positive anomaly (138.0 mm) where adding up the daily rain amounts gives us 56mm [50]. Topographically, however, it could make sense, so it goes on the watchlist but isn’t thrown out.

Tanzania, south eastern Kenya, Uganda, South Sudan CHIRPS shows above average rainfall over large areas of the region, with April values 100-200 mm above average. Kilimanjaro (TZ) shows 400 mm above average. CHIRP and ~15 stations contributed to these data. Extreme rainfall was reported in many of these areas. Some of the most damaging events were in Nairobi and Mombasa (KN), Kasese and Kampala (UG), Mbeya, Zanzibar, Kilimanjaro, and Morogoro (TZ).

Angola There is a station on the West coast just inland of another station that shows half the value of the coastal one. The station seems to be anomalously low for flooding reports in the area and the values CHIRP assigns to the area. It is on the watchlist.

Madagascar Tropical cyclone Fantala skirted Madagascar’s northern coast, resulting in the extremely high station value [51]. There is another station on the SE coast that reported a high value where CHIRP reported low values-it is now on the watchlist.

Ethiopia There is a station in the NW of the country that is reporting a high rainfall value in the middle of very low values; it doesn’t have an impact on the final CHIRPS product, but will go on the watchlist to see what happens next month.

Chile Two stations, CHIRP, and CHIRPS final show above average rainfall in the Santiago area. Anomalies are 20-100 mm, which put rainfall in the 95th percentile (2+ standard deviations from the April mean). Floodlist reported that heavy rains and floods in Santiago left 2 people dead and 10 missing

Southern Brazil, Uruguay, Eastern Argentina CHIRPs final, from support by 30+ stations and CHIRP showed rainfall anomalies of 150-300mm in this region. CHIRPS totals in south Brazil are similar to INMET April accumulations (150-500mm). Link to report CHIRP shows a SE-NW oriented swath of heavy rain. The heavy rainfall was associated with several extreme events through the month, with greatest impacts in Uruguay. In early April, Argentina media reports claimed that over 500 mm of rain has fallen in some areas, including Alejandra in Santa Fe, San José de Feliciano in Entre Ríos, in the space of 4 days. Uruguay River rose to concerning levels. Then in mid April, more heavy rain occurred in Uruguay (150-180mm in 24 hours) and was accompanied by a tornado. 7 people died and 3,000+ people were displaced. Continuation of the severe conditions led to more flooding and displacement of 10,000 people.

Brazil Below average rainfall for much of the country (exceptions are south and north regions). CHIRPS shows rainfall as 25 to 75mm below average for most areas, with enhanced deficits (up to 150 mm anomalies) in States of Tocantins, Maranho, and Para. This general pattern is similar to the anomalies shown by INMET, Brazil’s Instituto Nacional de Meteorologia: Link to map

Australia While mostly dry, there were some moderate rains (more rain that usual - ~10-20 mm more on average) in Western Australia. [52]

South East Asia Despite an overall drought across South East Asia[53][54], Papua New Guinea experienced higher than normal rain in the north [55]. CHIRPS shows more precipitation in Indonesia (Sulawesi Selatan and Kalimantan Barat) than CHIRP alone, although not significantly above average.

Eastern China & Southern Japan Heavy rains in China and Japan are reflected in the CHIRP as well.[56][57]

Taiwan EWX classifies Taiwan as China (likely due to GAUL) - worth noting that while the PRC would be happy with that classification, Taiwan would not.

**Reality Checks update** Several station reports were removed from CHIRPS final product for April 2016. A list of these stations can be found on the Station WATCHLIST (link under Helpful Links at top of page)

March 2016

Somalia CHIRPS has 50 new stations reporting rainfall observations in Somalia, thanks to FAO SWALIM. Previously, CHIRPS relied on satellite information (CHIRP) and influence from stations in the general region to give information about Somalia rainfall. The new stations were helpful in portraying how Somalia's MAM 2016 rainy season began. Parts of southern Somalia began with negative March anomalies of ~20 mm. This is corroborated by analyses based on other data that indicate poor March and April rainfall in the region. See FEWS NET Hazards Report and discussion below for more information. Another benefit of the Somalia station addition is that some stations contributed information in northeast Kenya (shown by the March decorrelation distance map in EWX).

Kenya, southeast Uganda, northern central Tanzania CHIRPS shows below average rainfall by 25 to 50 mm, with some areas like Kilimanjaro (TZ) up to 100 mm below average. General agreement with ARC2 March anomalies. A station near Kilimanjaro at Moshi (37.1E,3.4S) reports only 13 mm rainfall in March, with an anomaly of -90 mm. The exception to CHIRPS and ARC2 agreement is central TZ, where ARC2 shows average to slightly above average and CHIRPS shows average leaning to below average. In that area CHIRPS uses two stations (32.8E,5S and 35.7E, 6.2S). These report anomalies of -32 mm and 9 mm, respectively.

Ethiopia The pattern for March rainfall anomaly looks similar to NOAA's ARC2 and Ethiopia NMA Maproom data. March rainfall was below average by 25 to 50 mm across southwest to north central Ethiopia. A minor difference between Ethiopia NMA data and CHIRPS (and ARC2) is that Ethiopia data shows slightly above average rainfall in areas along west boundary with Sudan and South Sudan.

South Africa and Lesotho Near Lesotho and Free State (South Africa), several stations report low values that are below average. ARC2 shows similar below average March rainfall in these areas.

Angola SASSCAL station at 13.4E, 14.8S reported much higher rainfall value than its neighbor. Happened in Feb 2016 also. Checked and explained by topographic gradient (~1000 m higher than its neighbor).

Namibia SASSCAL station value at 17.3E, 20.4S removed due to reporting 0 mm next to neighbor station report of 72 mm. Same issue occurred in Feb 2016. Station is now on watch list.

Brazil Southeastern Brazil, along the coast, received very heavy rainfall, leading to flooding [58]. In general, the Amazon got more rainfall this month than it has in past months – however some of the values are suspiciously high. INMET, the Brazilian met agency, reports values closer to 300-400 mm, but CHIRPS is reporting values 400-700 [59]. There are two stations in the Amazon that drove this value up, both due to our own methodology – both stations had several days missing and we interpolated the values. One station (seq num 205630) reported 618mm but we filled in 709mm; the other (seq num 205638) reported 608mm but we filled in 650mm. We recommend taking out a different station in Brazil, in the north east (seq num 21432). This station has historically been lower than it should and significantly alters CHIRP into lower CHIRPS values. This month, the value was 21mm, surrounded by 200-400mm. The area should be wetter in the final CHIRPS. This station report was removed from CHIRPS March 2016 and the station is now on the watch list.

Columbia The round egg-shaped feature is still in Columbia, an artifact of smoothing with the station value. There are also quite a few stations reporting 0mm along the northern coast, backed up by other station data [60].

Peru CHIRPS reports a lot of rain in the north, not backed up by TRMM [61]. However, flooding reports back up CHIRPS in catching this flooding event [62].

Pakistan and surrounding region Above average rainfall, comes from ~18 stations. Other areas nearby that CHIRPS shows with above average rainfall are far northern India (~5 stations), Afghanistan (0 stations), and Jammu Kashmir (0 stations), and eastern Oman (~11 stations). Spatial extent can be attributed to CHIRP and to influence of stations mentioned above. Pakistan’s heavy rain was reported via reliefweb.int in early March in parts of Balochistan, with concerns of flash flooding. The storms continued into mid March across 6 provinces and led to flash floods, inland floods, and landslides that collapsed houses and other buildings. In the first half of March 121 people were killed and 127 were injured in Pakistan.

Balkan Peninsula countries Serbia, Montenegro, Macedonia, Bulgaria and Greece. CHIRPS shows above average rainfall (25 mm to 100 mm above average). Largest anoms were in Serbia and Montenegro. More than 50 stations reported the wet conditions across the region. According to Floodlist.com, heavy rainfall in early March created emergency situations in Serbia after flooding and landslides damaged homes and transportation links in central and eastern parts of the country. By the end of March over 1000 families received aid from the Red Cross.

Switzerland, Austria, and parts of Italy, Spain, and Portugal CHIRPS shows rainfall was 10 to 50 mm below average. Supported by ~50 stations in total and CHIRP.

Southeast Asia Above average rainfall in Indonesia indicated in CHIRPS was backed up by news reports of flooding [63].

Australia ~6 stations, especially in the west and all from the GHCN dataset, showed either zero or significantly lower values that surrounding stations, CHIRP, or weather reports.

Contributors: Emily Williams, South America; Laura Harrison, Europe and Central Asia; Libby White, Southeast Asia and Oceania.

February 2016

Tajikistan, Kyrgyzstan, Uzbekistan, Afghanistan, Pakistan The general area around Tajikistan has very suppressed precipitation, with z-scored ranging from -1.5 to -3. Reports detail that this level of supressed rainfall may lead to a drought, impacting the water supply to neighboring countries [ http://www.azerbaijannews.net/index.php/sid/241799989]. The values are verieid by reports (ex/Dushanbe, Tajikistan at 7.40mm for hte month [ https://www.wunderground.com/history/airport/UTDD/2016/2/16/MonthlyCalendar.html?req_city=Dushanbe&req_statename=Tajikistan&reqdb.zip=00000&reqdb.magic=1&reqdb.wmo=38836]). 'Note: The decorrelation map has a strange V-like artifact over Tajikistan, which may be impacting the correlation of the stations.'

Indonesia & Malaysia Significant rainfall and flooding has been reported across Indonesia and Malaysia. Values have been verified by various reports [64] [65]. Some pixels in Indonesia show negative anomalies in a sea of positive anomalies (when working in anomaly space), but when the actual precip values are added up for the month at that station (ex//Semarang [66]), we find that the values are ok.

Philippines The Philippines are several months into a significant drought, backed up by reports [67].

Angola There is a large positive anomaly in Angola. The southern tip of it has a report of flooding [68]. Much of the rain fell in the last dekad of February, with the first two showing negative or no anomalies.

Madagascar The northern tip recieved 121mm of rain in one day [69]; 700,000 people in the south were impacted by the supressed rainfall, and 30,000 in the north by flooding [70].

Mozambique Large are of high precipitation in Zambezi region observed in CHIRPS that was not seen CHIRP product. It was determined that a nearby station perturbed the climatology which corresponded to a land surface elevation gradient.

Brazil and Argentina CHIRPS compared well, visually, with the monthly Met Services of each country.

South American CHIRPS Mean regional statistic hit a another new low for February which is consistent with the last 5 month.

January 2016

Zimbabwe, Mozambique, Madagascar January CHIRPS shows large negative rainfall anomalies in these countries, on the order of 100-200 mm below average. These are more than 2 standard deviations from the mean in southern Madagascar, Tete province (Mozambaique), Mashonaland provinces (Zimbabwe), and Southeast province (Zambia). Enhanced dryness in these areas is part of a spatially large and persistent condition affecting southern Africa that is due to El Nino. See the Joint EC, FAO, FEWS NET and WFP Statement on El Niño Impact in Southern Africa

Tanzania, northern Mozambique, northern Madagascar CHIRPS reports wet anomalies of more than 100 mm. These were historically extreme (more than 2.5 standard deviations above the mean, in the ~98th percentile) in Mozambique's Cabo Delgado province and Tanzania provinces Mtwara, Lindi, and Morogoro. The largest anomalies were in Morogoro (+400mm) and areas in northern Madagascar including the Comoros Islands (150-300 mm). The very wet conditions is supported by 15+ stations. In Tanzania's Dodoma province heavy rain, strong winds, and flooding from 17-18 January destroyed 145 houses and affected 2,800 people. Previously, extreme wet conditions destroyed 1,500 homes in northern Mozambique. Due to the intensification of heavy rain in January, 5 fatalities occurred in Cabo Delgado province.

Gabon, Congo, and northern DRC CHIRPS shows rainfall as below average in January in western areas of central Africa. The estimates come from CHIRP and also ~12 stations in the area. NOAA's ARC2 data also reports a drier than normal January 2016 in this area.

More stations in Africa CHIRPS The station coverage has improved in southeast Africa. From November 2015 to January 2016 the number of reporting stations doubled in Botswana (7 to 14) and Zambia (8 to 17) and increased greatly in Angola (1 to 17). Improvements come from integration of the SASCAL dataset.

Brazil, Paraguay In central eastern and southern areas in Brazil and Paraguay CHIRPS reports wet anomalies of 100-150 mm and to +300 mm above average. More than 60 stations reported these conditions, in addition to CHIRP. According to FloodList more than 215,000 people were affected by flooding in January in Rio de Janiero, Mato Grosso, and Parana states (Brazil).

South America (northern/eastern and Amazon area) CHIRPS estimates January rainfall as being around 100mm below average from the Atlantic coast, through northern Brazil, and into southern Columbia. Some coastal zones of French Guinea show 200-300mm dry anomalies. The spatial pattern of dryness in CHIRPS is similar to what the satellite-based CHIRP data estimates, but the dry anomalies are also sourced from approximately 20 stations across the region (mainly in Brazil and to the east)

Columbia Columbia's Pacific coast area show very dry anomalies (200-400mm below average). Caution should be applied to the data in this zone as the anomalies are historically extreme (more than 2 standard deviations below the mean) but there are no stations reporting in the immediate area. Interesting effects seem to be coming from CHIRP and neighboring stations. Influence from neighboring stations is heavy in the southern section, as CHIRP shows above average in that area. Dryness in the northern section, which climatologically is drier, seems to come mainly from CHIRP.

Florida (US) and Cuba Extreme wet conditions in January in southern Florida and parts of Cuba. Rainfall was 100-250 mm above normal. The dense station coverage in the United States supports these estimates. Many areas experienced rainfall higher than the 95th percentile. Some areas broke records for January. In Fort Myers, FL for example it rained more than 8.5 inches in January (average is less than 2 inches). This followed their hottest Christmas on record.

California (US) January CHIRPS shows above average rainfall in northern California, with 50-150mm positive anomalies for most areas north of 35N. These estimates come from CHIRP and more than 40 stations. Depending on location rainfall ranged from the 68th to 90th percentile compared to previous January CHIRPS estimates.

Contributors: Laura Harrison (Africa, South America, Latin America, U.S.); 2/19/16

December 2015

Zimbabwe Thus far into the 2015-2016 season, drought conditions have affected many countries of Southern Africa, including Angola, South Africa, Botswana, Zambia, Zimbabwe, Lesotho, Swaziland, and Mozambique. This was due to a delayed start and erratic distribution of rainfall since the start of the season in October. December rainfall was a key contributor to season total deficits in Zimbabwe. CHIRPS shows large rainfall deficits across the country ranging from 50 to 150 mm below the December average. The largest deficits are in central-eastern and northern Zimbabwe. There is high confidence in CHIRPS data in Zimbabwe due to agreement from 7 stations, CHIRP, and ARC2 in most areas.

Mozambique CHIRPS shows below average for most of the country, with anomalies in northern region of -15 to -75mm and larger deficits in the central and southern region (-75 to -150mm). The northern region dryness is in contrast to what NOAA’s ARC2 and RFE2 products show for December, which is above average rainfall (50-100 mm anomalies) in Cabo Delgado province. The CHIRPS dryness seems to be coming from CHIRP, and from influence of a station in northwest Mozambique. Another difference between CHIRPS and ARC2 is in central-southern Mozambique in southern parts of Manica and Sofala provinces. Here, ARC2 shows rainfall surplus and CHIRPS shows deficit. These deficits in Manica seem sourced mainly from CHIRP and from nearby Zimbabwe stations, as a GTS station in Manica did not report a large deficit. There is congruent evidence of very poor December rainfall in southern Mozambique, with reports of deficits from three stations and agreement with CHIRP and ARC2.

Zambia CHIRPS shows that most of Zambia, in particular the southern parts, experienced below average December rainfall. Ten of the twelve stations reporting to CHIRPS in Zambia reported deficits. The worst deficit reported was near Lusaka at 181 mm below average. Poor December rainfall may have exacerbated problems with food security that were previously identified in western, southern, and eastern areas. Overall, ARC2 and CHIRPS are not in agreement in Zambia. ARC2 shows above average conditions in northwest and north central provinces. Both products agree that southeast province was below average.

Tamil Nadu, India: CHIRPS continue to show the reported continued anomalous rainfall in southern India. However, rainfall was not as severe as November, and most rainfall seems to have occurred early in December. Two stations in and around Puducherry, south of Chennai, reported 200-500 mm above the average rainfall.

Kazakhstan/Northwest China: CHIRPS reported very wet conditions in Kazakhstan, especially near the border of China's Xinjian province. Rainfall appears to be two to three times the average, with one station on the border reporting six times the average rainfall. Seven stations in the area reported above average rainfall. CHIRP generally agreed with CHIRPS, but not to the extent of the station on the border. No news reports regarding especially heavy rainfall in the region were found.

Philippines CHIRPS shows the very wet conditions that occurred in the Philippines in December due to multiple major storms. Rainfall surpluses of 250 to 900mm are shown in the data. December totals along the east coast ranged from 650 to 1400mm. According to a report from Emergency Management, the rain was caused by a cold front, dragged into the country by Typhoon Nona (international name: Melor) and Tropical Depression Onyok, which hit the country in succession in mid-December. The December storms were responsible for at least 45 fatalities.

East Indonesia/Papua New Guinea CHIRPS shows large rainfall deficits that range from 150 mm to 300 mm below average for December. This area received only 30 to 70 percent of average December rainfall, based on the CHIRPs climatology. These conditions are consistent with those experienced for several months in the region. Drought and erratic rainfall here are linked with El Nino. Impacts through the end of 2015 were depletion of food sources and lack of water for household use. These problems have caused increased disease risk due to poor sanitation and use of non-sustainable coping mechanisms, such as households selling needed assets.

Southeast China Above average rainfall in southeast China is due to more than 25 station reports and also CHIRP satellite-based estimates. The wet conditions are linked to the series of major storms, including Typhoon Nona/Melor that moved through the Philippines and the South China Sea.

United States The Midwest and Southeast US continued with above normal rains creating flooding in the Midwest. CHIRPS captured this rainfall with large areas of the country in excess of 150 mm for the month.

Colombia A large region in the center of the country, "the blob", was estimated to have received above normal rainfall after station values were applied. There was no indication of the blob in the CHIRP data field. A group of station on the northeast end of the blob may have caused the creation of this above normal rainfall pattern. There is a group of three stations with very low values of 2 mm and then one 30km to the west with a higher reading of 179mm. We think there may be some effect of the autocorrelation field causing this pattern when there is a large differential between these to estimates. The pattern is seen in the previous three months but to a lesser extent. The pattern is not seen in previous years since these data contain many more stations in the region and wash out the effect. We will continue to investigate this phenomenon.

South America Paraguay, Brazil, Argentina, Urugay: Flooding in these four countries. Asuncion, Paraguay saw a lot of flooding shown in the r-checks file[[71]] ; South Brazil saw flooding [[72]]; these reports are backed up by TRMM [[73]].

Sao Paulo, Brazil: Report says that Sao Paulo received less than normal rain in December [[74]]; pre-station CHIRPS labels the area as wet, but station data backs up a negative anomaly, and CHIRPS did a good job of incorporating the station data to drive down the final CHIRPS value in the immediate area. This lack of rainfall for December is very localized.

Brazil: The northern parts of Brazil (part of the Amazon Basin) have been in a terrible drought in 2015, which has continued in December; this patterns is backed up by Brazil’s INMET [[75]].

Peru: Artifact of flooding in northern Peru backed up by reports [http://floodlist.com/america/heavy-rain-peru-landslides-floods]

Notes on CHIRPS in South America Station artifacts: There are circular artifacts in Southern Brazil and Paraguay, similar to the ones seen in previous months (see November's "Recurrent CHIRPS Issues"); they seem to be station-driven as they don’t exist in CHIRP.

Regional statistics

• Global CHIRPS Maximum exceed 2200 mm for a new high for December. This is still under investigation.
• South American CHIRPS Mean hit a new low for December but this is in agreement with reports from the continent.
• Southern Africa CHIRPS Max hit a new low for December but this is in agreement with reports from the continent.

Contributors: Emily Williams (South America), Libby White w/Laura Harrison (Asia), Martin Landsfeld (U.S., Latin America, Statistics); 1/19/16

November 2015

United States: CHIRPS shows the very wet conditions that occurred across the South and southern Midwest. November rainfall was 100-200 mm above average in northeastern Texas, eastern Oklahoma, Arkansas, Missouri, and in Georgia, North Carolina, and South Carolina. Monthly totals in Arkansas and Missouri were the highest on record in November 2015 (record dates to 1895). CHIRPS shows below average rainfall in coastal Oregon and coastal northern and southern California.

Mexico, Belize, Guatemala, El Salvador: The region encompassing the Yucatan Peninsula and south to the Pacific received heavy, above normal rainfall. A Guatemala station near the Caribbean Sea, Puerto Barrios, reported 680mm, which is 15 inches above normal. Reports from Guatemala explain that much of the heavy rain occurred in the second half of November. It led to dangerously high river levels and flooded communities in Alta Verapaz region. Flooding displaced thousands of people in Guatemala, Belize, and Mexico.CHIRPS also shows Panama as receiving above average rainfall.

Southern Africa: November CHIRPS shows widespread dryness across most of southern Africa, with anomalies of -30mm to -80mm. Some of the affected areas experienced below normal rainfall in October (South Africa, Zimbabwe, Mozambique, Angola). A below average rainfall season tends to occur in the region during El Nino conditions. The November dryness contributed to substantial season-to-date negative anomalies that pose a risk to cropping and pastoral activities.

Uganda, Kenya, Tanzania: November totals were 75mm to 150mm above average across most of Uganda and the Lake Victoria Basin. Similar magnitude anomalies occurred in other areas of southern Kenya and east and west Tanzania. The November wetness marks the second consecutive month month of anomalous rainfall in Uganda and west Tanzania, according to CHIRPS and the NOAA ARC2 product (Oct ARC2; Nov ARC2)

Qatar and Saudi Arabia: Areas received record rainfall in November, but CHIRPS did not pick it up. Qatar's Met Department reported a year's worth of rain in Doho (80mm) on Nov 25th. There were no Qatar stations reporting in CHIRPS. The satellite-based CHIRP product did not show sign of the wet events. There were several stations in Saudi Arabia reporting to CHIRPS in areas with reported flooding, but only one of them had a large anomaly (Hafr Al-Batin, at 90mm above normal). The influence of this particular station is not seen in the final CHIRPS product. Overall, CHIRPS shows a slightly wetter than average November in northern Saudi Arabia and no sign of the historic events noted here.

Southern Europe: CHIRPS shows below average rainfall across the region. Italy was particularly dry, with northern Italy at 150mm below average.

India: Exceptional amounts of rainfall were reported in southern India, and CHIRPS captured these anomalies well. Heavy rains occurred in areas that typically receive 150mm to 500mm in November, driving totals instead up to 2 times those amounts. The Chennai area received ~1000mm in November, according to news reports and to a GHCN-v2 monthly station that reported to CHIRPS. Some areas had the wettest November in 20 years.

East Asia: CHIRPS reported very wet conditions in southeast China, stretching from Guangi to the East China Sea coast near Shanghai. Anomalous wet conditions are also shown in Japan, South Korea, and the DPRK.

Indonesia: While most of Indonesia has below average rainfall values in November CHIRPS, there is an interesting rainfall dipole feature. Eastern Malaysia, Brunei, and western parts of Kalimantan, Indonesia show above average rainfall. The wetness is reported by multiple station observations and from CHIRP.

Brazil: Dryness persisted across the Amazon Basin in November. See October and September posts below. CHIRPS shows positive rainfall anomalies of ~100mm in areas of southeast Brazil (Sao Paulo and Rio de Janeiro). The wet November coincided with the collapse of a dam that released massive amounts of sludge and some toxic waste through the Rio Doce.

December 2015

Recurrent CHIRPS issues

1. Circular-shaped artifacts are seen in the data, anomalies, and z-scores of CHIRPS data in southern Brazil. These tend to be centered at station locations. The issue needs more evaluation, but the origin seems to be from the CHPclim, which has similar but smaller features in the region. These features may increase in size according to the spatial influence of stations.
2. Coastal data artifact along North America's west coast. CHIRPS is generally a land-only product, but in some areas the coverage extends 1 to 3 pixels beyond the coastal boundary. Along the West Coast these pixels have lower climatological mean values than the data on land. This results in substantially different rainfall estimates and anomalies. The differences may be due to extension of coverage of the CHPclim based on TRMM, and should be examined further. In the meantime, CHIRPS users may want to consider clipping their data to coastal boundaries to remove the artifact.

Contributors: Laura Harrison; 12/21/15

October 2015

United States: A storm complex that tapped into the moisture from Hurricane Joaquin off the south-eastern coast of the US hit the Carolina's, dumping 12-24 inches of rain (picked up in CHIRPS)[76]. Louisiana and Texas, in addition, were hit with the remnants of Hurricane Patricia, receiving a lot of rain (also visible in r-checks) [77].Finally, a dry-spell it the midwest showed up as well [78].

Mexico: Hurricane Patricia hit the south-west coast of Mexico, and rapidly downgraded, as shown in CHIRPS and backed up by FEWS early warning data [79]. Two stations however reported very low values (4 and 5 mm) along the northern border of Patricia's path. One of them, 400141, is blocked by mountains so might have a rain shadow. The other, 400984, however, is on the coast and is a station to keep an eye on. The path of Patricia can be seen here [80].

El Salvador, Honduras, and Nicaragua: The bay bordered by these three countries (where Choluteca is) has a very high station next to a low one. This is right where a severe gradient is that goes from high precipitation quickly to low. The mountains around this bay might act as a rain shadow. In El Salvador and Honduras, we see a similar pattern as the mountains block rain coming up from the south and a steep gradient occurs from high rain to very low.

Haiti: Haiti is showing a positive rain anomaly in the north west. While this area has been doing well, other reports show average instead of a positive anomaly. Might be good to keep an eye on it. [81]

East Africa: October CHIRPS is in general agreement with rainfall estimates from NOAA CPC ARC2 and RFE2 datasets in east Africa. Differences in magnitude occur in parts of Sudan and South Sudan, where CHIRPS estimates are approximately 30% lower than ARC2 and RFE. The products are all in agreement that October rainfall was above average in Sudan, South Sudan, and Uganda (CHIRPS, ARC2, and RFE2). The source of lower CHIRPS values may be (1) a drier climatology in October CHIRPS compared to ARC2 climatology and (2) features in the CHIRPS algorithm that lead to conservative estimates and low bias. Also, in an area of reported heavy rains with flooding (border of Ethiopia, Sudan, and South Sudan) there appears to be a drying influence of two GHCN-v2 stations in southeast Sudan used in CHIRPS- these reported low but reasonable values locally, but reduced the CHIRP estimate in the high rainfall area. Ethiopia contained 8 stations this month, a big improvement from the past few months.

West Africa: In October 2015, most of the station reports that contribute to CHIRPS in West Africa are from GHCN-v2, a source of monthly data that is highly ranked due to its quality control. CHIRPS compared well with CPC 30 day anomaly from the FEWS Hazards Report, 10/29/15, except in Guinea and Sierra Leone where CHIRPS is much drier.

South Africa: Stations between Lesthoso and Swaziland reported lower values than CHIRP estimated. The stations reduced the final CHIRPS which is in agreement with the FEWS Africa Hazards Report, 10/29/15, abnormal dryness polygon over the region.

Brazil: CHIRPS reports below average rainfall across much of the nation, with exception of heavy rainfall that occurred in Porto Alegre, Rio Grande do Sul state. Major flooding occurred in that area [82]. The rainfall deficits during October covered much of the Amazon rain forest and are highly concerning given the magnitude and persistence of drought conditions since 2014. The Amazon drought is reported as the worst in the past 80-100 years [83] and has created water shortages in major cities and rural areas [84][85]. Reality Checks monthly CHIRPS comparison identified the South America mean rainfall in September 2015 and October 2015 as being the driest since 1981, when the CHIRPS record began, and Brazil deficits play a major role in these continental scale deficits.

Asia: CHIRP did not perform well with Typhoon Mujigae, between Hong Kong and Hainan on Oct. 5-7th. The stations reported the precipitation amounts and CHIRPS estimates were increased in the area.

A GSOD station on northern border of Pakistan recorded 529 mm for the month. A neighboring station reported 179 mm. A news report claimed record rainfall in the area so we decided to keep the measurement.

Contributors: Laura Harrison (South America), Marty Landsfeld (Asia), Emily Williams (North and Central America, Hispanola), all-of-the-above and Shrad Shukla (Africa); 11/17/15

September 2015

Vietnam: Tropical Storm Vamco brought a lot of rainfall to central/northern Vietnam/Laos/Thailand (300+ mm with flooding and fatalities). CHIRPS picked up significant rainfall in Northern Vietnamn (around Hanoi), but CHIRPS's pattern is a bit north of the reports. [86] [87]

China and Taiwan: Typhoon Dujuan brought torrential rainfall to Northern Taiwan and Eastern China; CHIRPS shows it in E. China but not much in Taiwan. [88] [89] Stations, though, seem to be reporting well so may be an interpolation problem with the climatology.

Japan: Lots of rain and flooding along Western coast and center [90].

Malaysia, Indonesia, Papua: Massive dry swaths; many large uncontrolled fires from slash-and-burn agriculture (could be good to keep an eye on for next month).

Columbia : Station in Cali, Columbia looks low but looked at previous months values and it looks fine. Diego confirmed it has been dry there in July and August. The rains are returning now he says. SQL commands: select * from precip_monthly4 where station_seqnum=20777 select * from precip_monthly4 where station_seqnum= 205576

Brazil : Near Sao Pablo all the stations are higher than CHIRP estimate. INMET rainfall map confirmed the higher values. Brazilian rainfall map can be found at: http://www.inmet.gov.br/portal/index.php?r=home2/index Click the Mapas de Precipitacao tab and then the Plus button at the bottom of the map and an end date and time period can be selected (30 dias).

*South America record rainfall deficit* : Station comparison graphs showed a very low CHIRPS mean for South America. /home/CHIRPS/diagnostics.etc/v2.0/marty/chirps.s_amer.stats.09.png But examining the CHIRPS didn’t reveal any errors in processing and given such a strong El Nino and the warm water in the eastern Pacific to the north, it we decided it was a real phenomenon. Also, stations in NW Brazil and Columbia verify the low precip values.

Ethiopia : Ethiopia contains only 3 stations. A special check was done on the contribution these stations had for CHIRPS data and anomalies. The 3 stations (2 were co-located) showed below average September rainfall and enhanced CHIRP deficits. As a result, CHIRPS September rainfall shows ~100 mm below average in Addis Ababa and Dire Dawa areas-- roughly 25% of average September rainfall. The CHIRPS September values were compared to data plotted with the Ethiopia Met Agency's MapRoom, which is described as being satellite estimates merged with ~600 stations for the country. Similar magnitude September 2015 anomalies are seen in CHIRPS and the Ethiopia data [91] for these areas. The stations were retained in CHIRPS.

Somalia, Uganda, Rwanda and Burundi: All had 0 stations reporting

Contributors: Emily Williams (Asia, Australia, Pacific Islands), Marty Landsfeld (South America, Africa), Laura Harrison (North and Central America, Africa); 10/19/15 - 10/23/15

August 2015

North Korea: Removal of a GSOD station. DPRK experienced flooding associated with seasonal rains in early August, and from Tropical Cyclone Goni on 22-23 August, affecting South Hwanghae and North Hamgyong Provinces ([92],[93]) . The two GTS stations in the country are in these areas and reported heavy rains, which the CHIRPS reflects near these areas. GSOD stations (~12) in rest of the country report below average rain, making August an overall poor month for rain in DPRK. This has likely exacerbated the problems associated with late start to seasonal rainfall-- in June DPRK declared they were experiencing the 'worst drought in a century.' There have been major population impacts in the region, perhaps due to a combination of weather and political forces. Suggest removal of GSOD station #274228: Report is 9.19 mm in area with flooding. [94]

South Korea: CHIRPS dry anomaly confirmed. Stations show low August rainfall (verified by news reports), which has created an overall poor season there [95]. Makes North Korea dryness believable also.

China: Some cases of good stations not influencing CHIRPS local values. Saw several instances when neighboring stations swamped what looks like reasonable above average rainfall reports from some stations. Led to below average CHIRPS values in these areas. Examining monthly decorrelation distance maps may help identify scope of problem.

Ghana: Concern about station reports and conditions. Several stations reported 0-10 mm in August. These had some influence on CHIRPS. Were deemed ok stations as they had reasonable values in earlier months and seasonal rains have been below average due to active ITCZ enhanced rains in an abnormally northern position. Note: In July 2015 Ghana had only 1 reporting station in CHIRPS, as compared to 5-13 in other months.

Ethiopia: Exceptional dryness identified by ranked z scores. Z score=-2.6, station value=160 mm, Ethiopia highlands (10.33N, 37.740E). Determined CHIRPS value in area was representative of conditions. Also that this is an area of potential concern that needs highlighting on Hazards report-- GeoWRSI shows crops were in reproductive phase in August; Prelim CHIRPS shows September 1-10 was below average; ARC2 shows below average thru September there also.

India: Incorrect wet anomaly in northern India. India's Met Department shows below average ([96]), but CHIRPS shows strongly above average. Due to combination of: 0 India stations in area + very wet observation in NE Pakistan (verified by reports) + wet station in China + CHIRP shows wet anomaly. Otherwise, CHIRPS correctly identified August rainfall deficits across most of India and surplus in Bhutan.

Chile: Atacama desert, possible problem. Reports say significant rain in Atacama desert ([97] ,[98]) , which rounds to 15 mm instead of 5; CHIRPS isn’t really picking it up as it’s a very fine difference, but as that area is a desert area, that small increase in rainfall resulted in massive flooding and evacuation. CHIRPS showed significant precipitation inland of Concepcion, which agrees with rain and snow reports ([99]). Santiago: CHIRPS wet anomaly confirmed. Report ([100]) details increased rain, which is showing up in CHIRPS.

Uruguay: CHIRPS wet anomaly confirmed. CHIRPS recorded above average rainfall for Uruguay for August 2015. The rainfall throughout the country, according to CHPClim, tends to be between 60 and 90 mm; however, CHIRPS reported it ranging from 190 to 240 mm, with the south-eastern coast receiving between 300 and 340mm for the month. This increase in rainfall is backed up by reports, including one from “floodlist” ([101]).

Burkina Faso (added 9/23/15): Station near capital (Ouagadougou) flooded in August, but CHIRPS didn’t pick it up. However, CHIRPS did pick up the rest of the flooding in the country.

September 2015

Notes on Rchecks resources

Regarding the rchecks-2.files: Reminder - The zscores in rchecks-2.files are not station zscores. They are zscores of CHIRPS data that has been placed at that station's pixel. Using the zscores in these files is helpful for identifying extreme CHIRPS that are caused by extreme station values. Using the zscores is not helpful for identifying stations that do not have influence much on CHIRPS BUT give bad reports (had concerns about this for some stations in Ghana, see above). We discussed routinely isolating a value that indicates this, so that we know which stations have issues. Basically we would do a sorting of the country information based on this value, like we do with the zscores (check.txt). Something to look into more. Also, we corrected a bug that limited the number of recheck text files. Now should have all countries.

Contributors: Laura Harrison, Marty Landsfeld, Emily Williams; 9/17/15

July 2015

Ethiopia: July’s r-check had quite a few high z-scores. Upon analysis, these discrepancies were coming from the highlands, near Addis Ababa, and south of Addis Ababa.
Station (10.33, 37.74; in town of Debre Markos) reported much lower than CHIRP and CHPClim, in the same way it reported low for August 2015. Station (8.86, 39.92; in town of Metehara Merti, near Addis Ababa) also reported much lower than CHIRP and CHPClim. ARC2 tells a similar story; ARC2 dictates the area having received 200-300mm[102]. ARC2’s anomaly map for July also roughly matched CHIRPS’ anomaly map, at a decrease of around -200m of normal[103].
One report stated “July’s seasonal rains did not come this year…” , while another confirmed that "the rain condition was ok for the first ten days during the month of June. It gradually declined and we started experiencing shortage in rain in July. But conditions are good in August…it has occurred several times in the past, including in 2005.”. The July rains (that didn’t come this year) tend to climb north-east across the highlands throughout June, July and August, the area showing a shortage in rain. It seems the stations are correct and Ethiopia experienced a drought this summer. However, due to the decreased number of stations since August 2014, it is possible that these stations are overestimating the level of drought.

Sudan: CHIRPS and CHIRP both indicate that in southwest Sudan, June was had normal rainfall, July was dry, and August returned to normal rainfall (aka summer rains came late). The proximity of the area to the Ethiopian highlands means it followed similar trends as seen in Ethiopia, as backed up by previous reports. HOWEVER, CHIRPS completely missed mass flooding in Darfur in July[104]; for that same time of mass flooding, CHIRPS reported a decrease in rainfall.

Burkina Faso: We may have a faulty station (or stations) in northeast Burkina Faso. The two stations are located at (14.03, -0.033; stn 277004); one reported 482 mm of rain, CHIRP reported 129, and CHPClim 117; the other station seems to bring the number ranges from 0-10. These stations combined, though, are driving up the CHIRPS rainfall estimates.
One report does state that regular rain started mid-July [105]. However, most reports indicate that the northeastern area had decreased, not increased, rainfall in July [106]; NOAA/FEWS NET reports for July show dryness as well in the west and southwest [107] [108] [109] [110] [111].

Guatemala: CHIRPS is fairly accurately picking up a drought in Guatemala, but may be overestimating it in some areas. Station (-88.59, 15.74) has a high value (154) compared to CHIRP (104), and yet CHIRPS is drug down for that pixel (84). There is a neighboring station in Honduras that has an extremely low station value that is most likely over-influencing CHIRPS, creating exaggerated estimates of low rainfall for Guatemala. Reports confirm the drought's severity: TRMM (anomaly and time series) shows drought in the north and west of the nation (-100- -200), in concurrence with CHIRPS (-200- - 300), and written articles confirm the precip data [112] [113]. CHIRPS is picking up the drought around El Salvedor and in southern Honduras, but again might be overestimating the drought in Guatemala.
Flooding occurred in July in Chinaulta (southeast) ; CHIRP and TRMM both reported higher than average rainfall in that area, but CHIRPS reported higher rainfall only along the coast and drought in Chinaulta. The underestimation of precipitation by CHIRPS might again be the influence of the station in the north of Honduras. It seems that stations are having too high an influence, especially when they are all reporting the same phenomenon and are then influencing another with the opposite (ex//drought all around, but flooding in Chinaulta).

Honduras: see above
CHIRPS shows a more extreme drought in the West than CHIRP shows, but TRMM reports similarly, suggesting CHIRPS is accurately reporting the drought and CHIRP underestimated it[114].

Contributors: Emily Williams; 9/23/15 - 9/24/15

June 2015

Honduras: CHIRPS reported Honduras having experienced flooding around the capital and the northern Caribbean coast. The flooding in the center was backed up by reports. However CHIRP reporting higher rainfall than the stations. Mid-June, Hurricane Bill formed along Honduras's northern coast, which could account for the flooding. However, NOAA/FEWS does not report any flooding, and in fact reports dryness along the Southwest of the country.

Nicaragua: CHIRPS picked up some significant rainfall (anomaly of +30-50mm) along Western Nicaragua. It was confirmed that the flooding seen in CHIRPS is roughly the pattern of flooding experienced on the ground [115]. NOAA/FEWS did not pick up this flooding in their reports [116].

Costa Rica: Costa Rica similarly experienced significant flooding in much of the country, also missed by NOAA/FEWS. However, it was picked up by TRMM.

Ethiopia: CHIRPS reporting lower-than-average rainfall for Ethiopia's highlands, which seems to be in line with the summer's drought. Compared to ARC1 estimates, CHIRPS might be overestimating the drought at this point, but it is nonetheless present. NOAA/FEWS have not captured the severity and distribution, and even declared "no drought" in Ethiopia at the end of June [117].

Kenya: Flooding in Nairobi that CHIRPS didn't catch [118]. Other general trends in climate are echoed by ARC1 [119]. There is a station in the southeast of Kenya (in the town of Mombasa) which reported a higher-than-average value for CHIRPS, but a low station value; this same area was subject to flooding [120].

In May, flooding in Mombasa, picked up by CHIRPS [121].

Madagascar: CHIRPS reporting higher-than-average rainfall along Madagascar's eastern coastline.

Senegal: One station is reporting an abnormally low value (7mm) for June, when CHIRP puts it around 100mm. However, Arc2 shows a decline in rainfall for that area in June [122]. The station looks okay for other months; may be good to keep an eye on though.

Mali: Station reporting a low value (99) in an area that tends to get 127; CHIRPS is reporting 139 for this area. The area is on the slope of a mountain, though, and on a rain gradient, so it's likely that the station is correct.

Ghana: CHIRPS failed to pick up flooding in coastal town of Accra during "biggest storm in the past 20 years". The station failed to pick it up, which is probably why CHIRPS didn't get it (station said 154mm, while the report said 250 mm in only the first 3 days.

Contributors: Emily Williams; 9/28/15

May 2015

Guatemala: There is a station in the far east of Guatemala which is reporting a significantly high rainfall value, but CHIRPS is reporting a value closer to CHIRP and CHPClim. There is, however, a station very near in Honduras which has an extremely low value which could be over-influencing CHIRPS at our station's location.
TRMM total rainfall anomolyis reporting lower-than-average rainfall for that period of time, but then a positive anomaly for June which aligns with our station.
However, TRMM's total rainfall time series from station values agrees with our station that is reporting higher rain[123], and disagrees with the Honduras station.

Honduras: The most notable station this month has a value of 1 in the North West of the country. However, the country as a whole had an anomaly of 100-200mm, lining up with TRMM values. The station is in a valley surrounded by mountains so it might be correct in that it received no rainfall there, but is something to keep an eye on.

Tajikistan: CHIRPS to picked up flooding in the Khatlon province of Tajikistan [124].

Kenya: CHIRPS is showing a high quantity of rain along the southern coast and boarder of Kenya. The ARC2 time series points up this claim, in addition to the estimates. Additionally, the RFE anomaly backs up the claim of high rainfall in the south, and low in the northwest [125].

Tanzania: CHIRPS and ARC2 both show an high positive anomaly of rain in Tanzania in the SE [126]. The RFE for the end of the month shows a negative anomaly for the same area [127], but a positive anomaly for the beginning [128]. Reports of flooding back up this claim [129].

Uganda: CHIRPS shows dryness through much of the country except for a high incidence of rain in the south near the lake. RFE and ARC2 show similar trends. ARC2 time series shows both the dryness just north of the lake (in correspondence with the low station value) and then the wetness to the west of the lake [130]. CHIRPS is correct for May.

Madagascar: Dry station on east (central/north) coast; ARC2 time series shows same dryness [131]; ARC2 month shows the same [132]. However, CHIRPS showing a lot of wetness along the rest of the eastern coast, but not backed up by ARC2. It seems like the coastal stations have been overreporting rainfall for May-July. ARC2 timeseries and month-estimates, RFE, and reports [133] show less rainfall than CHIRPS.

Burkina Faso: Country received high rainfall in West according to RFE and ARC2 [134] [135]. Station in CHIRPS shows the same story; however CHIRP is showing dryness across the country. ARC May estimates agree there should be more rainfall in the West. Seems like this station is being drowned out by dry stations and should have a higher influence on the area to make it come up as wet instead of dry/average.

Mali: Station in south of country shows wet values but is also being drowned out by surrounding drought area, making the area look average instead of wet.

April 2015

Cote D'Ivoire and Ghana: CHIRPS is struggling again to pick up anomalous wet periods when surrounded by dry areas. There were stations reporting wet values surrounded by stations reporting dry values, and CHIRPS didn't allow for the high value to significantly impact the area around it; RFE [136] and ARC [137] both indicate wetness for the southern part of the country, which CHIRPS under-reports.

Eastern Africa: CHIRPS did a good job in picking up the significant wetness stretching along the Eastern coast of Africa. ARC and CHIRPS are in agreement, where RFE is reporting much drier conditions throughout Kenya and parts of Tanzania.

Kenya Kenya was fairly wet in August. RFE and ARC show wet conditions in northern and western Kenya, though drier conditions in southern and eastern Kenya. CHIRPS isn't picking up the dryness. All the z-scores that stood out, however, are for stations that reported lower rainfall values than CHIRPS shows. Seems CHIRPS isn't heeding local station signals enough and relies too strongly to influences of surrounding precipitation conditions.

Honduras: There is a station that received nearly zero rain in April, but this is backed up by the RFE time series points.

Dominican Republic: CHIRPS picked up that very little rain fell along the northern and eastern coasts of the Dominican Republic.

Tajikistan: CHIRPS shows lower-than-average rainfall in north along ridgeline, and higher-than-average rainfall in the western-central portion of the country. Stations are reporting higher values for rain than the weather records [138] (130 vs 71). Difficult to verify if CHIRPS is accurately reporting or not due to limited precipitation data to compare with. Would be good to have NOAA's RFE png blown up a bit to see better whether our results correlate [139].

Contributors : Emily Williams, 10/16/15