Estimating rainfall variations in space and time is an important aspect of drought early warning and environmental monitoring. To this end, scientists at the U.S. Geological Survey Earth Resources Observation and Science Center, working closely with collaborators at the University of California, Santa Barbara Climate Hazards Group, have developed a quasi-global (50°S–50°N, all longitudes), 0.05° resolution, 1981 to near-present gridded rainfall time series: the Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) data archive. The rainfall estimates contain satellite-based fields adjusted by station observations from a variety of sources.

 

As of May 1st, 2014 version 1.8 of CHIRPS is complete and available to the public.

 

Since 1999, U.S. Geological Survey (USGS) and University of California, Santa Barbara (UCSB) scientists, supported by funding from the U.S. Agency for International Development (USAID), the National Aeronautics and Space Administration (NASA), and the National Oceanic and Atmospheric Administration (NOAA), have been developing techniques for producing rainfall maps especially where surface data is sparse. Focusing primarily on Africa, this work supported drought monitoring efforts by the USAID Famine Early Warning Systems Network (FEWS NET). These data served a number of early warning objectives. The 30+ years of CHIRPS makes it suitable for trend analysis.

 

Two CHIRPS products are produced operationally: a rapid preliminary version, and a subsequent final version. The preliminary CHIRPS product is available, for the entire domain, two days after the end of a pentad (2nd, 7th, 12th, 17th, 22nd, and 27th). The preliminary CHIRPS uses only a single station source, GTS. The final CHIRPS product takes advantage of several other stations sources and is complete sometime after the 15th of the following month. Final monthly, dekad, pentad and daily products are calculated at that time.