An Analysis of Momentum Flux Budgets and Profiles in a Large-Eddy Model

Abstract

Momentum fluxes and variances play an important role in the characterization and forecast of weather phenomena, but cannot be measured easily. A subdivision of the flux changes into budget terms by the underlying physical processes, such as buoyancy transport, can assist in understanding their sources and influences. Momentum flux and variance budgets for SAM, the System for Atmospheric Modeling, have been implemented and are compared to existing budgets from other simulations. A tool for the visualization of these quantities from three-dimensional grid data has been developed to show and explain their distribution in conjunction with shallow cumulus and stratocumulus clouds. For the shallow cumulus case, we have found opposite fluxes within clouds and in the cloud halo regions as well as a significant contribution in the environment. In a small region within the cloud layer we have upgradient fluxes.