Rainfall Estimation From Combined Microwave And Infrared Satellite Observations

Abstract

Introduction Rainfall retrievals from passive microwave instruments are capable of producing very accurate instantaneous rainfall estimates. They suffer, however, from the poor sampling available from polar orbiting spacecraft. The current microwave sensor on board the DMSP spacecraft observes a point near the equator approximately 26 times per month. Of these 26 overpasses, it senses precipitation an average of only 10% of the time. With this in mind, it is not surprising that large errors in monthly rain estimates are possible even though the retrievals appear very accurate at the time of overpass. In this paper we discuss a technique for calibrating the less correlated, but far more frequent infrared observations from geostationary platforms with passive microwave observations. Examples over Darwin, Australia and the western Pacific are used to illustrate the merits of such a technique.