Study of Climate Change Mechanism in Cloud-Capped Planetary Boundary Layer over the Arctic Ocean Using a Hierarchy of Models Resolving Cloud Formation Processes

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This project is a study of the radiative, microphysical, and dynamic properties of low stratiform clouds with the objective of improving the treatment of radiative transfer in general circulation models (GCMs) under varying cloud conditions, and to improve the parameterization of cloud formation and cloud properties in GCMs. A low overcast ("arctic stratus") is characteristic of the Arctic Ocean region, particularly in summer. These low clouds affect the radiation budget of both the free atmosphere and the sea ice surface. Their structure results from an interaction among the large-scale transport of heat and moisture into the Arctic, the macrophysical processes of boundary layer turbulence, and the microphysical and optical properties of liquid water droplets. In this project radiative cloud forcing and the transport of momentum, heat, and moisture will be modeled using a recently developed three-dimensional large eddy simulation model with explicit formulation of cloud microphysics. The model will be extended by introducing an adaptive grid near the top of the cloud layer, and adapting a two stream radiative scheme to parameterize cloud inhomogeneities and their effect on the radiation field.