A NUMERICAL EXPERIMENT OF SQUALL-LINE FORMATION

Abstract

The formation of a prefrontal squall line is studied, based on a numerical method of solving the modified equation of motion, continuity (mass and moisture content), and thermodynamics simultaneously. Due to the limited capacity of the electronic computer used (IBM 650), computations in this experiment are necessarily simplified, and this preliminary study is made for two idealized cases both of which consider conditions in advance of an intense cold front. The first case treats moist air at low levels with dry air aloft; the second considers a strong southerly jet-like flow at low levels. From results obtained, it is shown that a significant factor for squall-line formation is the unbalance between thermal wind and actual wind shear. Also, the role of a strong southerly flow at low levels is indirect and appears to be that of supplying moisture from ocean areas.