On the Sensitivity of Convective Cold Pools to Mesh Resolution

Abstract

It is well recognized that triggering of convective cells through cold pools (CPs) is key to the organization of convection. Yet, numerous studies have found that both the characterization and parameterization of CP effects in numerical models is cumbersome—in part due to the lack of numerical convergence with respect to the horizontal mesh resolution, Δx, obtained in typical cloud-resolving simulators. Within a comprehensive numerical convergence study we systematically increase the horizontal resolution in a set of idealized large-eddy simulations. Our analysis captures key CP processes, namely free propagation, frontal collision and merging of gust fronts. We characterize the numerical convergence of tropospheric moistening rates, gust front vortical strength and propagation speed, and the amplitude of the lobe-and-cleft instability. The understanding gained from this analysis may help develop robust subgrid models for CP dynamics.