Retrieval of rainrate over rough sea surfaces as measured by the Advanced Microwave Precipitation Radiometer (AMPR)

The Advanced Microwave Precipitation Radiometer (AMPR) was deployed during the Tropical Ocean Global Atmosphere (TOGA) Coupled Ocean-Atmosphere Response Experiment (COARE) from January 4 to February 24, 1993. The configuration of the AMPR instrument limited the scanning angle to 45 degrees left and right of nadir. Because of this configuration, one-half of the data acquired are nadir or quasi-nadir looking for which the influences of emission and half-space scattering of rough sea surface are significant. For tropical ocean rainfall measurements, sea surface condition is important, because it determines the lower boundary condition for microwave radiative transfer. A two-scale composite rough sea surfaces model developed by Wu and Fung was used to characterize tropical ocean´s rainfall brightness signatures with the use of acquired sea truths (field collected sea surface wind speed and sea surface temperature data) when available. The results of computation with the use of acquired atmospheric data from other instruments was used to develop a retrieval algorithm by which the AMPR measurements (brightness signatures) can be used to infer the measurements of rainrate, cloud liquid water content and other physical parameters. The developed analysis technique and the results of data analysis is presented