Long-Term Merged Climate Rainfall Products

Several climate rainfall products, which merge rainfall estimates from a variety of satellite and ground-based sources are currently available starting in January of 1979 and continuing through the present. These include the Global Precipitation Climatology Project (GPCP) dataset and CPC's Merged Analysis of Precipitation (CMAP). Both of these datasets incorporate rainfall estimates from several satellite-based retrievals, ground-based rain gauges, and numerical model output.

While the combination of data from these multiple sensors/sources provides long-term climate rainfall datasets suitable for climate studies, there are a number of issues affecting their use for some climate applications. These include discontinuities in the component data sets, differences in the calibration methods, and the methodology used to weight the individual rain estimates. An example of climate differences resulting from these issues is shown by a comparison of tropical mean rainfall from the GPCP and CMAP datasets. To look at these differences yourself or to determine if differences between these datasets is an issue for a specific climate application, we suggest you go to our interactive product intercomparisons page [Plot Intercomparison].

GPCP [More information] [Plot Intercomparison]
The GPCP merged dataset combines rainfall estimates from a variety of satellite and in-situ data sources including both emission-based and scattering-based passive microwave retrievals from SSM/I, infrared-based satellite retrievals, estimates from the TIROS operation vertical sounder (TOVS), and gridded ground-based rain gauge observations produced by the Global Precipitation Climatology Center (GPCC).
GPCP (Satellite only) [More information] [Plot Intercomparison]
The GPCP merged satellite dataset combines rainfall estimates from a variety of satellite data sources including both emission-based and scattering-based passive microwave retrievals from SSM/I, infrared-based satellite retrievals, and estimates from the TIROS operation vertical sounder (TOVS).
CMAP (Obs + NWP) [More information] [Plot Intercomparison]
The CMAP merged dataset also combines rainfall estimates from a variety of satellite and in-situ data sources. In addition, this version of the CMAP dataset also uses precipitation from Numerical Weather Prediction (NWP) models. The NWP data is used primarily to fill in gaps at high latitudes.
CMAP (Obs only) [More information] [Plot Intercomparison]
The CMAP merged dataset also combines rainfall estimates from a variety of satellite and in-situ data sources. This version of the CMAP dataset does not use NWP data. As a result, some gaps occur in high latitude regions.
CAMS + OPI [More information] [Plot Intercomparison]
The CAMS-OPI merged dataset combines the satellite derived OLR Precipitation Index (OPI) with raingauge data from the Climate Anomaly Monitoring System (CAMS).