Title: The Modulation of Aerosol Impacts on Convective Clouds

Abstract:

Past studies have reported that enhanced aerosol concentrations can result in an increase, decrease or little change to the precipitation produced by convective clouds. This makes the impacts of aerosols on deep convective precipitation very difficult to predict in both current and future climates. This precipitation response appears to be modulated by various factors including (1) environmental characteristics such as the relative humidity, convective available potential energy and soil moisture, (2) aerosol characteristics including aerosol type and the vertical and horizontal distribution of aerosol particles, and (3) cloud characteristics such as cloud type and cloud life cycle. An implication of such modulations is that similar cloud types impacted by the same aerosol loading may produce negative through positive precipitation feedbacks due to the environment in which they are developing.

Several examples of the way in which factors (1) through (3) can modulate aerosol impacts on surface precipitation will be presented. More specifically, the role of the vertical location of aerosol layers on squall lines, the moderation of aerosol effects on supercells by dry layers, the role of storm life cycle in modulating the impacts of aerosols on hurricanes, and the regulation of aerosol impacts on post-cold frontal cumulus by static stability will be examined. These process studies have all been conducted using the Regional Atmospheric Modeling System (RAMS), a versatile cloud-resolving model with a sophisticated microphysical and aerosol parameterization scheme. Evidence of the modulation of aerosol impacts on deep convection in observational data will also be presented.