A Possible Use of Multi-Sensor Satellite Observations for Inferring the Drop Collection Efficiency of Warm Clouds

Abstract

This study proposes a combined use of spaceborne cloud profiling radar, shortwave and microwave measurements provided by the A-Train constellation of satellites to investigate the warm-rain collection process in low clouds. The continuous collection model is employed to interpret the relationship between the observables of CloudSat, MODIS and AMSR-E measurements. The theoretical formula representing the collection process involves the collection efficiency factor, which is then inferred from these observations by exploiting the differing sensitivities of these sensors to cloud drop sizes. The collection efficiency implied ranges from the order of 0.001 to that of 1.0, and is systematically larger than estimated by traditional methods when updraft velocity is ignored in the continuous collection model. The collection efficiency is also found to increase with columnar effective particle radius in a manner consistent with classical relationships. These results suggest that the new observations provide a gross measure of the real collection efficiency factor on the global scale.