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A Subgrid Representation of Precipitating Marine Boundary Layer Clouds

Leung, L.R., and Ghan, S.J., Pacific Northwest National Laboratory; Feingold, G., Cooperative Institute for Research in the Atmosphere, Colorado State University
Ninth Atmospheric Radiation Measurement (ARM) Science Team Meeting

A subgrid parameterization is being developed to account for subgrid variations of precipitating marine stratocumulus clouds in general circulation models (GCMs). The method assumes an idealized form for the probability density function (pdf) for the cloud variables and predicts/diagnoses the parameters describing the pdfs. A level 2.5 turbulence closure model is used to calculate turbulence fluxes. Cloud-water-related turbulence fluxes are estimated using a partial cloudiness scheme that includes rain water. Subgrid contributions to the cloud microphysical conversion processes are determined by integrating the appropriate expressions over the pdf. Simulations performed by a two-dimensional Cloud Resolving Model (CRM) with a detailed cloud microphysics scheme have been used to guide the development of the subgrid parameterization. This subgrid parameterization is being implemented to a single-column model and a GCM. Sensitivity experiments are being performed to determine the impacts of the subgrid representation on the simulation of marine boundary layer clouds and drizzle.

Note: This is the poster abstract presented at the meeting; an extended version was not provided by the author(s).