A method of improving mesoscale predictions of the marine stratocumulus evolution during DYCOMS II

Besides the lack of routine measurements over the ocean, the problem of accurate predictions of marine clouds is emphasized by the models' limitations as well as incomplete understanding and parameterizations of major physical processes governing the cloud evolution. The DYCOMS II field program conducted in July 2001 off the southern California coast and subsequent LES results offer the possibility of using aircraft and satellite data to evaluate regional and mesoscale models such as MM5, COAMPS, and WRF as well as for testing their ability to predict the microphysics and turbulence structure of the marine coastal clouds. A method has been developed which uses satellite cloud-temperature measurements, satellite sea-surface temperature measurements, satellite-derived winds, and buoy data to improve predictions of the cloudy marine layer. This approach provides more accurate initial conditions of the offshore marine layer depth, temperature, and moisture fields over the ocean that lead to intense development of clouds. The method has been applied to nocturnal marine stratocumulus off the southern California coast and verified using aircraft data. The method has been compared to a WRF 3DVAR technique that can assimilate asynoptic data, including aircraft and satellite data collected during the DYCOMS II program.