ESRL/PSD Seminar Series

The CloudSat satellite is part of the A-train satellite constellation observing the Earth and its atmosphere from a sun-synchronous orbit at an altitude of about 700 km. While the primary goal of the CloudSat’s nadir pointing cloud profiling radar (CPR) operating at 94 GHz (W-band) is to provide global information on macrophysical and microphysical properties of clouds, it also proved to be a useful tool for quantitative estimations of rainfall. Since W-band radar signals are strongly attenuated in liquid phase, special radar remote sensing techniques, which use attenuation effects as input information, are utilized for rain rate retrievals. Currently CloudSat products include rain rate estimates use path integrated attenuation (PIA) over water surfaces for which radar backscatter in absence of rainfall is relatively stable. No rainfall products are currently available over land. To overcome this limitation a reflectivity gradient method to infer vertical profiles of rain rate from W-band radar measurements was developed. This method does not require PIA estimates and thus is applicable to observations above any surface. For validation purposes the experimental CloudSat retrievals over land using the reflectivity gradient were compared to the standard operational rain rate estimates from the National Weather Service ground-based scanning precipitation radars. The comparisons were performed for collocated in space and time measurements during the CloudSat overpasses over the ground-based radars. The comparison results show generally good agreement between rain rates derived using the traditional ground-based and the novel satellite radar approaches.