Convection and precipitation under various stability and shear conditions: Squall lines in tropical versus midlatitude environment

Abstract

This study investigates the sensitivity of the structure and intensity of squall lines to the vertical profile of temperature and moisture that are intended to represent a tropical, oceanic and a midlatitude, continental environment by conducting a set of numerical experiments with a nonhydrostatic atmospheric model at a convection-resolving resolution. In the experiments the vertical distributions of convective available potential energy (CAPE) for air parcels originating at various heights are controlled by changing relative humidity for the tropical and the midlatitude condition. It was shown that the strength and areal extent of updrafts within the simulated squall lines are significantly regulated by environmental temperature lapse rate. A condition with a larger lapse rate leads to the development of widespread, strong updrafts. The difference in the vertical profile of buoyancy for lifted air parcels is key to delineating the difference in the updraft statistics under different thermodynamic conditions. In contrast, it was found that the precipitation amount is controlled by the vertical distribution of CAPE. The precipitation amount increases with the increase in the depth of the layer having a significant amount of CAPE.