GPCP 2.5-Degree Monthly Precipitation Data Set

The Global Precipitation Climatology Project (GPCP) is an international project designed to provide improved long-record estimates of precipitation over the globe. The general approach is to combine the precipitation information available from several sources into a final merged product that takes advantage of the strengths of each data type. The GPCP has promoted the development of an analysis procedure for blending the various estimates together to produce the necessary global gridded precipitation fields. The currently operational procedure is based on Huffman et al. (1997) and has been used to produce the GPCP Version 2 Combined Precipitation Data Set, covering the period January 1979 through the present.

The current data set provides two final products, the combined satellite-gauge precipitation estimate and the combined satellite-gauge precipitation error estimate. The complete data set, which includes the input and intermediate data files, contains a suite of 27 products
providing monthly, global gridded values of precipitation totals and supporting information for the 26-year period January 1979 through the present.

The primary product in the Version 2 data set is a combined observation-only data set, that is, a gridded analysis based on gauge measurements and satellite estimates of rainfall. There are a total of 27 fields in the data set providing information from the individual and intermediate estimates, including estimates of RMS random error.

This data set is the successor to the GPCP Version 1 Combination. The Version 2 combination includes precipitation estimates from TOVS, permitting filling data voids at high latitudes that occurred in Version 1, and estimates from OPI, permitting extending the combination to months before SSM/I data are available (July 1987). The TOVS estimates are included by combination with SSM/I at mid-latitudes, and climatological scaling against gauges at high latitudes. For months without SSM/I data a monthly and regionally varying linear regression algorithm is used to adjust the OPI estimates, which are then used over the entire globe in place of the SSM/I estimates.

The Version 2 Data Set contains data from several contributing centers:

1. GPCP Polar Satellite Precipitation Data Centre - Emission (SSM/I emission estimates),
2. GPCP Polar Satellite Precipitation Data Centre - Scattering (SSM/I scattering estimates),
3. GPCP Geostationary Satellite Precipitation Data Centre (GPI and OPI estimates and rain gauge analyses),
4. NASA/GSFC Satellite Research Team (TOVS estimates), and
5. GPCP Global Precipitation Climatology Centre (rain gauge analyses),

The Global Precipitation Climatology Project (GPCP) is an element of the Global Energy and Water Cycle Experiment (GEWEX) of the World Climate Research Program (WCRP). The 1DD is produced by the GPCP Merge Development Center (GMDC), located at NASA's Goddard Space Flight Center in the Laboratory for Atmospheres.