Sensitivities of Maritime Tropical Trimodal Convection to Aerosols and Boundary Layer Static Stability

Abstract

A trimodal convective cloud distribution is commonly observed within the tropics due to the tropical-mean thermodynamic environment. The goal of this research has been to examine the integrated impacts of thermodynamic and aerosol properties on both the convective environment and the properties of the cloud modes themselves. This has been achieved by using LES experiments in which various thermodynamic and aerosol environments were independently and simultaneously perturbed. The key conclusions from this study are 1) large amounts of aerosol loading and low-level static stability suppress the bulk environment and the intensity and coverage of convective clouds; 2) cloud and environmental responses to aerosol loading tend to be stronger than those from static stability; 3) the effects of aerosol and stability perturbations modulate each other substantially; 4) the deepest convection and highest dynamical intensity occur at moderate aerosol loading, rather than at low or high loading; and 5) most of the strongest feedbacks due to aerosol and stability perturbations are seen in the boundary layer, though some are stronger above the freezing level. These results underscore the importance of considering the thermodynamic environment’s impact on aerosol-induced convective invigoration while highlighting the dominance of aerosol impacts on the trimodal distribution and revealing synergies between thermodynamics and aerosols.