A Comparison of Two-Dimensional and Quasi-Three-Dimensional Simulations of a Tropical Squall Line

Abstract

Abstract Results of a simulation of a tropical squall line which allows three dimensionality on the scale of convective elements, shows many similarities with those of a two-dimensional simulation. Differences are 1) The quasi-three-dimensional model produces less front-to-rear acceleration of updraft air and rear-to-front acceleration of downdraft air; 2) The horizontally averaged vertical mass flux and momentum flux profiles show sharper low-level peaks in two-dimensions; 3) The ratio of the maximum to minimum vertical velocities is larger in the quasi-three-dimensional simulation; 4) There is more of a cellular structure in the vertical plane perpendicular to the line in two-dimensions; and 5) The ratio of ice to liquid water is greater in the quasi-three-dimensional simulation. An unexpected result is that very little of the air feeding the rear low-level downdraft originates from ahead of the system, even in the quasi-three-dimensional simulation. Strong vertical mixing of the inflow air occurs so th...