Aerosol – Cloud Interactions during GoAmazon and TRACER: Does Deep Convection Respond to Pollution Similarly in the Tropics and Sub-Tropics?

The impact of aerosols on deep convection is complicated and, at times, is highly debated. Rather than focusing on single convective event, field campaign, or aspect of the cloud population, this study uses diverse observations from two field campaigns to explore whether aerosols have a systematic impact on several macrophysical characteristics of congestus and deep convection in the tropics and sub-tropics.

Our analysis uses data from two recent DOE ARM-funded field campaigns that were focused on increasing our understanding of aerosol-cloud interactions in regions impacted by pollution and had remarkably similar observations: Observations and Modeling of the Green Ocean Amazon 2014–2015 (GoAmazon) and Tracking Aerosol Convection Interactions Experiment (TRACER). Given that environmental changes also impact convection, we reduce the environmental variability in our analysis by clustering time periods during each campaign based on their environmental conditions. Within those environmental clusters, we analyze time periods during each field campaign that are characterized as having low, moderate, or high pollution based on their ultra-fine and fine aerosol concentration.

Some of the convective characteristics that we are analyzing include cloud top height, anvil depth, precipitation accumulation and rate, echo top heights, and characteristics of the drop size distribution. In general, TRACER was much more polluted and had much less precipitation than GoAmazon. Preliminary results indicate that trends in some of these convective parameters are opposite in the two campaigns. For example, precipitation is more common during TRACER when the aerosol load is high while precipitation is more common during GoAmazon when the aerosol load is low. An overview of these precipitation results and other results will be included in our presentation.