Modulation of Aerosol Impacts on Convective Clouds (Invited Presentation)

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 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 depending on 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. Results from both modeling and observational studies will be discussed.