Observationally constrained estimates of bulk entrainment rate for evaluation of large-eddy simulation
Abstract
The mixing of dry environmental air into rising convective parcels plays an important role in determining the depth and subsequent lifecycle of convective clouds. Cloud entrainment rates have also been identified as a critical factor for climate model sensitivity. In this study we use observational estimates of bulk entrainment rate, which provide an integrative measure of both the atmospheric thermodynamics and cloud macrophysical properties, to evaluate large-eddy simulations (LES). A simple entraining plume model, constrained by cloud radar observations, is used to estimate the bulk entrainment rate for shallow convective clouds. This algorithm is applied to observations from the ARM Southern Great Plains (SGP) site and to output from 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, and role of forward radar operators.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.A21K2867J
- Keywords:
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- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSESDE: 3310 Clouds and cloud feedbacks;
- ATMOSPHERIC PROCESSESDE: 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSESDE: 3314 Convective processes;
- ATMOSPHERIC PROCESSES