Simulation of an Observed Squall Line with a Meso-Beta-Scale Hydrostatic Model

Abstract

This paper reports on simulations of an observed squall line with the meso-beta-scale hydrostatic PERIDOT model. An attempt is made to answer the question of what model changes are necessary to roughly simulate a squall line with a hydrostatic model lacking explicit microphysics. A qualitatively satisfactory simulation is obtained by modifying the physical package of the model and by increasing the resolution compared to that of the operational model. Sensitivity experiments are conducted in order to determine the necessary components for the simulation of the squall line. The authors find that both increased resolution and a downdraft parameterization are required. The energetics of the inner circulation of the squall line are investigated using the best simulation. The main supply for the rear to front flow is identified as conversion of potential energy into kinetic energy. which is linked to the line-normal horizontal gradient of perturbation pressure. This result agrees with the conclusions of the sensitivity experiments and with previous studies on the important role played by the density current in squall-line propagation.