69 Cloud Radar Constrained Estimates of Bulk Entrainment Rate for Evaluation of Large-Eddy Simulations

Monday, 28 August 2017
Zurich DEFG (Swissotel Chicago)
Michael Jensen, Brookhaven National Laboratory, Upton, NY; and T. Toto, S. Endo, and A. M. Vogelmann

The mixing of dry environmental air into rising convective parcels plays an important role in determining the depth and subsequent lifecycle of convective clouds. A simple entraining plume model, constrained by millimeter-wavelength cloud radar observations, is used to estimate the bulk entrainment rate for shallow convective clouds (Jensen and Del Genio 2006). This algorithm is applied to observations from the ARM Southern Great Plains (SGP) site and to output from large-eddy simulation (LES) produced as part of the LES ARM Symbiotic Simulation and Observation (LASSO) Workflow. The comparison of bulk entrainment rates computed from observations and model output provides a new stringent metric for the evaluation of the boundary layer thermodynamics and cloud macrophysical properties in LES. We will present examples of the algorithm applied to active shallow cumulus observed at the SGP site, comparisons to LES under different conditions, the sensitivity of the comparison to the model thermodynamics and cloud properties, possible extensions to additional radar observed constraints and role of forward radar operators.
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