Aerosol-Cloud-Radiation Interactions in Atmospheric Forecast Models

摘要

The long-term goal of this research is to gain a deeper understanding of how atmospheric aerosols affect the transmission of radiation through the atmosphere and influence cloud properties. The scientific objectives of this project are to identify the specific manner in which atmospheric aerosols determine cloud properties and to represent these interactions in atmospheric models. The technological objective is to develop state-of-the-art instruments for aircraft sampling of aerosols that advance the long-term goals of the project. The investigators conducted comprehensive aircraft sampling of atmospheric particles and radiative and cloud properties. These samplings were complemented by laboratory investigations and theoretical analysis. The Marine Stratus/Stratocumulus Experiment (MASE-II) was carried out in the eastern Pacific Ocean off Monterey, California, during July 2007 with the CIRPAS Twin Otter. Comprehensive measurements were made of aerosol and cloud properties in areas both perturbed and unperturbed by local emissions. Sixteen flights were made, for a total of 70 flight hours. We have analyzed data from 13 individual clouds, 5 of which have evidence of ship exhaust. Observational data on aerosol-cloud-drizzle relationships in marine stratocumulus were analyzed. The data demonstrate, in accordance with those from other field studies, that increased cloud drop number concentration and decreased cloud-top effective radius are associated with increased subcloud aerosol concentration. Modulation of drizzle by variations in aerosol levels is clearly evident. Simultaneous aircraft and A-Train satellite observations have been used to quantify the precipitation susceptibility of clouds to aerosol perturbations in the eastern Pacific region.