Sensitivity study for the interpretation of Doppler signal of space-borne 95-GHz cloud radar

This paper provides preliminary study of the global distribution of ice cloud properties from CloudSat. CloudSat data was analyzed using relationships between radar reflectivity (Z_e) and ice cloud properties derived from ship-bome lidar/radar measurements [l]-[4]. The retrieval results were further compared to that obtained by a different approach combining CloudSat and CALIPSO to understand and evaluate their features from the observed similarities and discrepancies between the two methods. For the CloudSat and CALIPSO data analysis, the extended lidar-radar algorithm of Okamoto et al, [5] [6] was used. The comparison results showed interesting features that mostly attributed to the difference in the sensitivity of CloudSat and CALIPSO. Especially noticeable was the detection of larger particle sizes at lower altitudes by the CloudSat and CALIPSO method compared to that obtained by CloudSat-only approach due to the fact that CALIPSO observes much smaller cloud portion at these altitudes (which often corresponds to horizontally oriented ice particles cases) than CloudSat does. Results for the sedimentation velocity retrieved by the CloudSat-only method showed positive results for the possibility of detecting Doppler signals of ice clouds from space as expected in future missions such as EarthCARE. But since many factors will contribute to its detection, development of reliable CloudSat and CALIPSO synergy applicable for clouds detected at least by either sensors will be necessary to extend this study to perform more sensitivity studies and further asses the potential use of space-bome Doppler radar data.