Upscale Impact of Mesoscale Disturbances of Tropical Convection on Synoptic-Scale Equatorial Waves in Two-Dimensional Flows

Abstract

AbstractSuperclusters on the synoptic scale containing mesoscale systems are frequently organized by convectively coupled equatorial waves (CCEWs). Present-day global models struggle to simulate multiscale tropical convection, and the upscale effects of mesoscale systems are not well understood. A simple two-dimensional multiscale model with prescribed two-scale heating and eddy transfer of momentum and temperature drives the synoptic-scale circulation, successfully reproduces key features of flow fields with a front-to-rear tilt, and compares well with results from a cloud-resolving model (CRM). In the scenario with an elevated upright mean heating, the tilted vertical structure of synoptic-scale circulation is still induced by the upscale impact of mesoscale disturbances. In a faster propagation scenario, the upscale impact becomes less important as a result of competing effects of eddy transfer of momentum and temperature, while the synoptic-scale circulation response to mean heating dominates, in agreement with cloud-resolving models. In the unrealistic scenario with upward?westward-tilted mesoscale heating, positive potential temperature anomalies are induced in the leading edge, which will suppress shallow convection in a moist environment.