A Comparison of the Results of a Two-Dimensional Numerical Simulation of a Tropical Squall Line with Observations

Abstract

A comparison of the results of a two-dimensional numerical simulation of a tropical squall line with observations shows good agreement in most respects. The two-dimensional model should provide a valuable research tool for understanding the physical processes that are taking place and for discovering the effects of different wind and thermodynamic environments on squall-line characteristics. In the simulation high pressure develops ahead of the system relative to that behind at most levels. The momentum flux is mainly confined to below 6 km and in the region of strong convection. The squall line is multicellular and significant perturbations are associated with convection embedded in the stratiform region. Considerable horizontal accelerations occur at large distances from the region of strong convection, away from the system aloft and towards it at low levels. The effect of excluding the ice phase in the simulation is shown to lead to cloud tops some 3 km lower than when it is incorporated. Although the upper-level flow is significantly different the low-level structure is not substantially changed by inclusion of the ice phase.