The Global Precipitation Climatology Project (GPCP) data set that was established by the World Climate Research Programme. The general approach was to combine the precipitation information available from each of several sources into a final merged product, taking advantage of the strengths of each data type. This data set was used for many years, currently with daily data in version 1.2 and monthly data in version 2.3.
The sources from which GPCP data are processed are measurements from ground stations and satellite data products. Infrared precipitation estimates are computed primarily from geostationary satellites (GOES - United States, Meteosat - Europe, GMS - Japan), and secondarily from polar-orbiting satellites (by NOAA, US). Additionally a merged set of infrared precipitation estimates by Geostationary Satellite Precipitation Data Center (GPSPDC) is used. Microwave oceanic precipitation estimates are based on emission from 19 Ghz channel and for land precipitation estimates from the 85 Ghz channel of the Special Sensor Microwave/Imager (SSM/I) data from the Defense Meteorological Satellite Program (United States) satellites that fly in sun-synchronous low-earth orbits. Low-Earth orbit estimates from the Atmospheric Infrared Sounder (AIRS data from the NASA Aqua), and Television Infrared Observation Satellite Program (TIROS) Operational Vertical Sounder (TOVS), and Outgoing Longwave Radiation Precipitation Index (OPI) data from the NOAA series satellites are also included.
Infrared and microwave satellite estimates of precipitation are merged with in situ measurements from rain gauge data from the Global Precipitation Climatology Centre's (GPCC) Monitoring Product of the Deutscher Wetterdienst (DWD), used as land-surface reference for the GPCP Satellite-Gauge Combination. Therfore the combined product includes gauge-bias corrections.
The daily and monthly rainfall data are in the NetCDF format. The monthly data is already available in version 2.3 and is updated every month, whenever the new GPCC Monitoring product is available. In addition to these monthly data there is also an absolute error. The data for the last 6 months may include the interim product, where the data quality is less secure. Please refer to the description of NOAA. For the daily data the version 1.3 is not yet officially released, which is why ICDC still offers the version 1.2. There are no error data given for the daily data.
Last data set update: June 1, 2017.