Impacts of Model Spatial Resolution on the Simulation of Convective Spectrum and the Associated Cloud Radiative Effect in the Tropics

Abstract

 In this study, we examine the resolution dependence of the convective spectrum in Community Atmospheric Model version 5 (CAM5) simulations, focusing on the transition from shallow to deep convection and the associated cloud-radiative effect (CRE) change. We first apply the bin method (percentile binning) on precipitation intensity to obtain the convective spectrum in the tropics. The same approach is also used in the column-integrated moist static energy (MSE) budget analysis. The binning results show that over the light-rain regime, the convective structure is dominated by shallow convection, functioning to destabilize the atmosphere by importing column-integrated MSE. The heavy-rain regime shows the coexistence of deep and shallow convection, which inclines to stabilize the atmosphere by exporting the column-integrated MSE. Moreover, we also note that the longwave (LW) component of CRE (LWCRE) is more sensitive to the change of model spatial resolution than the shortwave (SW) component of CRE (SWCRE), characterized by a stronger response in the coarser resolution run over the heavy-rain regime. The resolution dependence of convective spectrum and CRE changes presented in this study highlights the importance of scale-aware cumulus parameterization design in climate models, which is not yet implemented in CAM5.