This dataset contains monthly combined satellite-gauge precipitaion data as well as error estimates. A climatology is also available. All data is available on a 2.5x2.5 degree global lat-lon grid.

The general approach used to create the final product was to combine precipitaton information available from each of several sources into a final merged product, taking advantage of the strengths of each datatype. The satellite data included microwave estimates based on Special Sensor Microwave/Imager (SSM/I) data, and IR precipitation estimates from geostationary and polar-orbiting satellites. Additional low-Earth orbit estimates include the TIROS Operational Vertical Sounder (TOVS) and OPI data from the NOAA series satellites. The gauge data are assembled and analyzed by the Global Precipitation Climatology Center (GPCC) of the Deutscher Wetterdienst and by the Climate Prediction Center of NOAA.

A more detailed description of the data can be found here.