An Analytical Study of Density Currents in Sheared, Stratified Fluids Including the Effects of Latent Heating

Abstract

A nonlinear analytic model is used to study the bulk characteristics of energy conserving density currents in stratified and sheared environments. The idealized representation of latent heating in a stratified flow is a unique feature that interactively couples the dynamic and thermodynamic fields. A stable stratification decreases the height of density currents but increases the corresponding propagation speed. In contrast, the density current is deeper and moves more slowly once latent heating is included. As for the effect of shear, the depth and the translation speed of density currents increase as the ambient shear varies from negative to positive (in the direction of propagation), with the exception of a strongly stable environment. A key addition to density current dynamics is the upper-level overturning circulation ahead of the system. This feature is very different from the blocked or choked upper-level structure found in the companion paper of Liu and Moncrieff. The distinction is attributed to the effect of different shear profiles on density current dynamics. These analytic results quantifying the role of shear and latent heating in density-current-like phenomena in the atmosphere should now be evaluated against high-resolution numerical simulations and observations.