Global precipitation map using satellite-borne microwave radiometers by the GSMaP project: Production and validation

This paper documents the production and validation of retrieved rainfall data obtained from satellite-borne microwave by the Global Satellite Mapping of Precipitation GSMaP) Project. Using various attributes of precipitation derived rom Tropical Rainfall Measuring Mission (TRMM) satellite data, lie GSMaP has implemented hydrometeor profiles derived from Precipitation Radar (PR), statistical rain/no-rain classification, nd scattering algorithms using polarization-corrected temperatures (PCTs) at 85.5 and 37 GHz. Combined scattering-based surface rainfalls are computed depending on rainfall intensities. PCT85 is not used for stronger rainfalls, because strong depress of PCT85 are related to tall precipitation-top heights. Therefore, for stronger rainfalls, PCT37 is used, with PCT85 used for rainfalls. With the suspiciously strong rainfalls retrieved rom PCT85 deleted, the combined rainfalls correspond well to the R rain rates over land. The GSMaP algorithm for the TRMM Microwave Imager (TMI) is validated using the TRMM PR,,round radar [Kwajalein (KWAJ) radar and COBRA], and Radar Meteorological Data Acquisition System (AMeDAS) precipitation analysis (RA). Monthly surface rainfalls retrieved rom six microwave radiometers (GSMaP_MWR) are compared the gauge-based dataset. Rain rates retrieved from the TMI (SMaP_TMI) are in better agreement with the PR estimates over land everywhere except over tropical Africa in the boreal summer. Validation results of the KWAJ radar and COBRA show a good linear relationship for instantaneous rainfall rates, while validation around Japan using the RA shows a good relationship in the warm season. Poor results, connected to weak-precipitation cases, are found in the cold season around Japan.