Owing to its -28-dBZ detection sensitivity, the CloudSat's Cloud Profiling Radar (CPR) presents a unique opportunity to measure light-to-moderate rains globally, and to complete the low end of the global rain distribution spectrum that is left off by the TRMM Precipitation Radar due to limited sensitivity to light-rain. Although the absorption of precipitation-size drops at W-band is significant, the CPR echoes from light rain will not abruptly disappear as soon as the liquid is encountered. Unfortunately, the attenuated, single-frequency radar measurements, such as those to be acquired by the CPR, by themselves cannot resolve the numerous intrinsic ambiguities in the rain profile retrieval sufficiently to guarantee unbiased estimates. One approach to overcome this problem is to perform quantitative rain retrieval by optimally combining the CPR measurements with the co-located AQUA AMSR-E radiometric measurements at comparable resolution.
The objectives of this proposal are to: (1) develop such a combined radar/radiometer retrieval algorithm; (2) perform accurate retrievals of vertical rain rate profile and mean drop size in light rainfall using this algorithm, and quantify the corresponding uncertainties; and (3) characterize the low-precipitation region of the global rain distribution spectrum.
