High resolution microwave radiometric signatures of mid-latitude and tropical rainfall

Combinations of both microwave and IR sensors, including a 14 GHz radar, are included on the upcoming Tropical Rainfall Measuring Mission (TRMM) satellite. This project is spurring advancements in precipitation profiling retrieval algorithms, which exploit the information contained in a set of multispectral equivalent blackbody brightness temperature observations along with ancillary information to account for cloud microphysical variability. Two NASA high-resolution imaging radiometers, the Advanced Microwave Precipitation Radiometer (AMPR; 10, 19, 37, 85 GHz), and the Millimeter Wave Imaging Radiometer (MIR; 89, 150, 183.3, 220 GHz) were flown in early 1993 aboard an ER-2 aircraft during TOGA-COARE over the tropical western south Pacific warm pool. The AMPR and MIR instruments are airborne simulators of the SSM/I and the recent SSM/T2 polar orbiting satellite radiometer systems. During 1991, the AMPRwas also operated during CaPE field experiments in central Florida. Observations from the two different climatic regimes show marked differences in the brightness temperature behavior associated with precipitation. Notably weak 85 GHz scattering T, depressions were characteristic of the tropical TOGA-COARE environment, where heavy rainfall can be generated from dominantly warm rain clouds containing very little ice content. The variable cloud microphysics characteristic of both warm and cold rain precipitation processes must be accounted for in precipitation profiling algorithms if reliable estimates of the latent heat are to be inferred from satellite-based rainfall measurements.<>