E1.8 Momentum Transport

Abstract

Transport of momentum throughout the atmosphere in large part controls the global circulation, and hence moisture and precipitation patterns. However, several momentum transport processes occur on scales much smaller than a global circulation model (GCM) grid box, and hence have to be parameterized. Improvements in the representation of subgrid momentum transport can lead to significant model improvements in the representation of wind stresses, moisture and precipitation patterns, and organized modes of variability. This project aims to improve the representation of subgrid momentum transport within convection and from orographic and convectively generated gravity waves, in order to improve existing biases in the representation of precipitation and surface stresses in the Energy Exascale Earth System Model (E3SM).

An overview of proposed E3SM improvements will be discussed here, in particular:

(a) verification of the parameterization of convective momentum transport within the deep convection scheme using WRF simulations, (b) introduction to a multiscale coherent structure parameterization (details will be discussed in a companion presentation by M. Moncrieff), (c) implementation of a new parameterization of orographic gravity waves, and (d) modification of the source spectrum parameterization of convectively generated gravity waves (CGGWs) in order to improve the representation of the Quasi-biennial Oscillation (QBO). We anticipate the above changes to E3SM will help to alleviate the following currently existing biases: double intertropical convergence zone, excessive wind stress over Southern Ocean, precipitation biases, including over tropical west Pacific and also improve the  representation of the Madden-Julian Oscillation.