Three-Dimensional Evolution of Simulated Long-Lived Squall Lines

Abstract

Abstract Simulations of squall lines, using nonhydrostatic convection-resolving models, have been limited to two dimensions or three dimensions with the assumption of along-line periodicity. The authors present 3D nonhydrostatic convection-resolving simulations, produced using an adaptive grid model, where the lines are finite in length and the restriction to along-line periodicity is removed. The base state for the simulations is characterized by weak, shallow shear and high convective available potential energy (CAPE), an environment in which longlived midlatitude mesoscale convective systems (MCSs) are observed. The simulated systems bear strong resemblance to many observed systems, suggesting that large-scale forcing, absent in the horizontally homogeneous environment, is not needed to produce many of the distinguishing features of midlatitude MCSs. In simulations without Coriolis forcing, the presence of line ends leads to mature symmetric systems characterized by a central region of strong convectio...