Use of millimeter and sub-millimeter wavelengths to retrieve cloud/rain information in tropical systems
Résumé
Millimeter and sub-millimeter wave radiometry offers new perspectives for the characterization of clouds and rain at global scale. Recent theoretical studies on the atmospheric sounding capabilities of space borne millimeter and sub-millimeter wavelengths have shown that cloud contents, rain detection and quantification, as well as properties of ice particles, can be derived from brightness temperatures simultaneously measured at different frequencies above 100 GHz with multi-channel retrieval algorithms (Jimenez et al ., 2007; Defer et al ., 2008). Millimeter and sub-millimeter waves are also adequate for a radiometer deployment at a geostationary location due to the relative small antenna size compared to those required at usual radiometric wavelengths (< 100 GHz) to assure geostationary observations at a convective-cell-size spatial resolution. We present here the skills in terms of rain detection, rain quantification and cloud content retrieval for different millimeter wave combinations including GOMAS-like (Geostationary Observatory for Microwave Atmospheric Sounding; Bizarri et al. (2005) - designed to provide precipitation estimate with a high temporal sampling, for now-casting) mission and CIWSIR-like (Cloud Ice Water Sub-millimeter Imaging Radiometer; Buehler et al., (2005) - dedicated to the observation and characterization of ice clouds from a polar orbit, focusing on climate studies) mission.
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