475 Passive Microwave Radiometer Channel Selection Based on Cloud and Precipitation Information Content Estimation

The information content of microwave frequencies between 5 and 200 GHz for rain, snow and cloud water retrievals over ocean and land surfaces was evaluated using optimal estimation theory. The study was based on large datasets representative of summer and winter meteorological conditions over North America, Europe, Central Africa, South America and the Atlantic obtained from short-range forecasts with the operational ECMWF model. The information content was traded off against noise that is mainly produced by geophysical variables such as surface emissivity, land surface skin temperature, atmospheric temperature and moisture. The estimation of the required error statistics was based on ECMWF model forecast error statistics. The results suggest a number of frequency bands most suited for the retrieval of (1) rain over oceans: 17-18, 32-45, 80, 135-150, 118.75 10-14 GHz; rain over land: 90, 135-140, 118.75 10-14 GHz; (2) snow over land and oceans: 135-155, 118.75 10-14, 195 GHz, (3) clouds over oceans: 42, 82-83 GHz; clouds over land: 90-100, 135 GHz. For radiometers designed for global and multi-season applications, several channels in all of the above frequency ranges would be desirable for optimizing channel impact on hydrometeor retrievals depending on the observed situation.

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