2.5 Observational Estimates of Convective Cloud Entrainment Rates

Monday, 9 July 2018: 11:30 AM
Regency D (Hyatt Regency Vancouver)
M. P. Jensen, Brookhaven National Laboratory, Upton, NY; and T. Toto and M. Starzec

The mixing of dry environmental air into rising convective parcels plays an important role in determining the depth and subsequent lifecycle of convective clouds. Despite its importance, the entrainment process remains poorly understood and its measurement and quantification are extremely difficult. We present an analysis of techniques for the estimation of bulk and height-resolved entrainment rates using a combination of radar observed cloud boundaries and vertical velocities as constraints on a simple entraining plume model. The techniques are applied to a spectrum of convective clouds from shallow cumulus, to cumulus congestus and deep convection using observations from the DOE Atmospheric Radiation Measurement fixed sites in the Tropical Western Pacific and Southern Great Plains and the mobile facility deployment during the GoAmazon 2014/5 campaign. The correlation of environmental controls to the estimated entrainment rates suggests a strong dependence on low-level convective available potential energy (a proxy for convective vertical velocity). Finally, the feasibility of using estimated entrainment rates for the evaluation of large-eddy simulations of shallow cumulus macrophysical properties and boundary layer thermodynamics.
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