A technique for estimating oceanic monthly rainfall has been developed and applied to data taken by the Special Sensor Microwave Imager (SSM/I) sensors and the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI). (URL: http://snowmelt.gsfc.nasa.gov/PSPDC/SSMI.rain.rate.html). The technique entails the use of a rain rate-microwave radiance relationship, an assumption of a mixed-lognormal rain rate distribution, and a beam-filling correction which accounts for a bias associated with non-uniform field-of-view of microwave sensors. The parameters of the mix-lognormal rain rate distribution are estimated from histograms of the microwave radiance.

In this talk, we will discuss the assumption of a mix-lognormal rain rate distribution, the beam-filling error correction and estimation procedures of monthly rain rate. Potential refinement to the beam-filling correction, as suggested by the recently acquired TRMM data, and the improvement in the estimation procedure will also be discussed.