Improving the Physical Basis for Updraft Dynamics in Deep Convection Parameterizations
Abstract
This article presents a new deep convective parameterization that determines cloud characteristics based on a specified cloud size distribution. The vertical profiles of cloud properties are determined by analytic equations, which formulate entrainment with an inverse relationship to cloud width. In line with recent studies of large eddy simulations (LES), cloud widths are assumed to be constant with height and vertical mass flux (M) characteristics of the clouds are therefore regulated by the vertical velocity profile. The parameterization is configured to work with existing cloud baseMclosure formulations, with the closure predicting the total cloud area rather than the cloud baseMdirectly. Analytic formula are also used to connect the vertical wind shear magnitude to the cloud size distribution, wherein larger shear magnitudes result in more numerous large updrafts than weaker shear magnitudes, which is in line with recent research results. The parameterization is compared against 10 deep convective LES with varying thermodynamic and vertical wind shear profiles. Results show dramatic improvements in the prediction of normalizedM, detrainment, and the properties of detrained air over the existing Zhang and McFarlane (1995) scheme. In particular, the new model is able to correctly portray the transition from a bottom‐heavyMprofile in weakly sheared environments, to a top‐heavyMprofile in strongly sheared environments.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Feb 01, 2021
- Source ID
- 10.1029/2020ms002282
Entities
People
- Guang J. Zhang
- Hugh Morrison
- John M. Peters
- Scott W. Powell
Organizations
- National Center for Atmospheric Research
- National Science Foundation
- Naval Postgraduate School
- United States Department of Energy
- University of California, San Diego