Numerical Simulations of Density Currents in Sheared Environments

within a Vertically Confined Channel

QIN XU

Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma

MING XUE

Center for Analysis and Prediction of Storms, University of Oklahoma, Norman, Oklahoma

KELVIN K. DROEGEMEIER

School of Meteorology and Center for Analysis and Prediction of Storms, University of Oklahoma, Norman, Oklahoma

(Manuscript received 26 September 1994, in final form 3 October 1995)

ABSTRACT

Numerical simulations are performed to study the kinematics and dynamics of nearly inviscid, two-dimensional density currents propagating in a uniformly sheared environmental flow within a vertically confined channel. In order to study the physical properties of the numerical solutions relative to those of theoretical predictions, the initial cold pool depth and shear are chosen to be either similar to or significantly different than those prescribed by the theoretical steady-state model. The authors find that, regardless of the model initial condition, the density current front reaches nearly the same quasi-steady state. The propagation speed, depth, and gross shape of the density current head in the quasi-steady state agree closely with previously published theoretical results and are independent of the initial depth of the cold pool provided that the total volume of cold air is sufficiently large. Physical interpretation of the results is provided based on theoretical analyses and numerical diagnosis of the energy, vorticity, mass, and momentum con-servation properties of the simulated flows.

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