Precipitation Data from Space for Hydrology: TRMM Era to GPM

Abstract:

Beginning shortly after the launch of the Tropical Rainfall Measuring Mission (TRMM) in late 1997, an increased emphasis was placed upon the development and evaluation of multi-satellite or “blended” techniques, that attempted to marry the best features of the precipitation estimates from the multiple, intermittently spaced passive (or active) microwave sensors, with the fine spatial and temporal sampling provided by the global operational geostationary imagers. These collective efforts have largely converged to the “motion-based” methodologies inherent in the designs of the current Global Precipitation Measurement (GPM) merged product (IMERG) and the Global Satellite Mapping of Precipitation (GSMaP) produced by the Japanese Space Agency JAXA. At their core, the performance of the multi-satellite techniques hinges upon the quality of the input precipitation data that is inherited from the various passive microwave (PMW) radiometers, such as the TRMM Microwave Imager, and the most recent GPM Microwave Imager (GMI). Typically, the radiometrically warm land surface background and its highly variable surface characteristics have limited the use of these sensors to the higher-frequency channels, which perform poorly for lighter rainfall and over complex, cold surfaces. This has limited the use of these data for hydrological modeling in watersheds where much of the streamflow originates from runoff of cold-season precipitation and snow. In this presentation, we will discuss some of the more recent changes to satellite-based precipitation techniques to account for land surface properties, including techniques that have been (or are under consideration for) the GPM over-land precipitation products.