Overview of overland satellite rainfall estimation for hydro-meteorological applications

This paper reviews current techniques on rainfall estimation from satellite sensor observations. The sensors considered in this study are the Precipitation Radar (PR) and radiometer (TMI) onboard TRMM (Tropical Rainfall Measuring Missio) satellite, the Special Sensor Microwave/Imager (SSM/I) onboard Defense Meteorological Satellite Program (DMSP) platforms, and infrared (IR) sensors onboard geostationary satellites. We present the physical basis and mathematical formulation of a newly developed combined radar-radiometer (PR/TMI) retrieval for TRMM and its application for overland rain estimation. Subsequently we discuss the current state-of-the-art in overland passive microwave (TMI and SSM/I) rain estimation techniques, and outstanding issues associated with the inverse problem. The significance of lightning information in advancing high-frequency rainfall estimation from passive microwave-calibrated IR retrieval techniques is discussed on the basis of newly developed techniques. Finally, current approaches are presented on merging the infrequent passive microwave-based rainfall estimates with the high-frequency, but lower accuracy, rainfall fields derived from proxy parameters (e.g., lightning and IR). The paper provides useful insights on satellite rainfall estimation and discusses issues and applications.