Process study of mixed phase Arctic stratus and associated aerosol effects

The longevity of climatically important low level Arctic stratus depends critically on cloud microphysics, which control liquid-to-ice conversion and precipitation rates. Since microphysical process rates in clouds are not measured directly, they can be evaluated via numerical modeling used to project our quantitative understanding of these processes onto observable cloud parameters. In this presentation, we assess our quantitative understanding of key microphysical processes using a detailed cloud model. The model is applied to a case study of a mixed phase stratus cloud observed over the sea ice on April 27, 2008 during the Indirect and Semi-Direct Aerosol Campaign (ISDAC), a recent Arctic experiment that provide ample opportunities for evaluating and improving cloud model and parameterizations, particularly in simulating the mixed-phase cloud regime. Results of simulated observable cloud properties are compared with aircraft measurements. A sensitivity study is used to determine model parameters and corresponding process rates that result in a better agreement with observations. Aerosol effects on cloud micro- and macrostructure of the cloud are also explored.