Aerosols and Deep Convective Clouds: Have We "Resolved" the Problem?

Zachary Lebo, Professor, Department of Atmospheric Science, University of Wyoming

The potential effects of changes in aerosol loading on deep convective cloud systems have received considerable attention in the recent literature, focusing on the response in precipitation, storm strength, lightning frequency, etc. In this talk, a review of the responses will be presented, focusing on two potential microphysical pathways by which an aerosol perturbation may modify the cloud and dynamical characteristics (i.e., the conventional “invigoration” mechanism and the modification of cold pool strength and/or structure). A detailed comparison between the simulated effects due to changes in aerosol loading and changes in environmental characteristics will be discussed; the effects due to changes in aerosol loading will be shown to be masked by even small changes in environmental characteristics. This conclusion suggests that observing such effects will be extremely difficult. Furthermore, the sensitivity of the model results to grid spacing will be explored and analyzed using a novel approach; this is an important consideration because many of the effects of changes in the aerosol loading are likely reliant on the entrainment/detrainment characteristics of deep convective cloud systems. Lastly, recent numerical solutions will be presented to confirm the cloud-resolving model simulations and pinpoint the processes in which deep convective cloud characteristics are likely to be most susceptible to changes in aerosol loading. These numerical solutions combined with the 3D cloud-resolving simulations will demonstrate that the “invigoration” mechanism is insignificant for strong deep convective cloud systems.