Unified Boundary Layer and Convection Parameterizations in Global Atmospheric Models

Joao Teixeira

Jet Propulsion Laboratory, California Institute of Technology, Pasadena

Abstract:

The parameterization of turbulent and convective mixing in global atmospheric models has been a major challenge in weather and climate research for several decades. In particular, different parameterizations are used, and often patched together artificially, for different types of convection: dry or moist, within the boundary layer or in the full troposphere. For example, the eddy-diffusivity (ED) approach has been relatively successful in representing the properties of neutral and stable boundary layers, and surface layers in general. The Mass-Flux (MF) approach, on the other hand, has been often used for the parameterization of shallow and deep moist convection. Recently, higher-order turbulence closures have been implemented in global models to represent boundary layer and shallow convection mixing. However, a fully unified parameterization of turbulence and convection (including deep convection) has never been successfully developed and implemented in atmospheric models.

In this presentation, we discuss recent approaches based on optimal combinations of the ED and MF parameterizations (EDMF), and of higher-order closures with the multi-plume MF approach, as potential solutions for the full unification of turbulence and convection in atmospheric models. We focus on regime transitions that are critical for weather and climate prediction, such as the spatial transition from shallow to deep convection over the tropical oceans, and the diurnal cycle of convection and precipitation (from shallow to deep convection) over tropical land. We discuss results from recent developments and implementations of these approaches that culminated in the first fully unified parameterization of turbulence and convection implemented in an atmospheric model.

Date 13 Feb 2025 

Time

• PT: 8:30 am
• ET: 11:30 am

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