Precipitation retrievals from passive microwave cross-track sounding instruments

Precipitation (rain and snow) is a key geophysical parameter. Due the temporal and spatial variability it is vital to exploit all available data sources, and in particular all available passive microwave sensors. This paper concentrates upon the development of a physical retrieval scheme to obtain precipitation estimates from cross-track passive microwave sensors (a.k.a. `sounders'). Initial studies into the impact of the variable Earth incidence angle upon the retrievals suggested that while changes in polarization were minimal, resolution played a greater part. Although the scheme was originally envisaged with 75 scan-position/surface type databases generated from satellite/surface observations, the final scheme utilizes a model-generated database with a single database; results from this scheme are presented. The paper finally presents some initial work from investigations into the next-generated cross-track retrieval schemes.