Climate-Scale Oceanic Rainfall Based on Passive Microwave Radiometry

In the microwave regime, the relatively low and stable emissivity of the sea surface serves as an excellent background over which brightly emitting hydrometeors can be distinguished. Space/time oceanic rainfall has been estimated from microwave radiometry using a simple radiative transfer model of an atmospheric rain column, a rain rate distribution to account for sampling deficiencies, and an empirical correction of the nonuniformly filled field of view of the microwave sensor. The microwave emission-based brightness temperature histogram (METH) technique has been applied to the Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSM/I) to produce over 25 years of monthly oceanic rainfall. The METH technique is described and the retrieved parameters are assessed. The inter-satellite calibration of microwave and DMSP SSM/I sensors provided a climate-scale oceanic rainfall time series capable of examining climate trends and variabilities.