Observational Assessment of Aerosol Impacts on Updraft Speed in Deep Convection

Aerosols influence cloud attributes, such as cloud development and convective dynamics, through their role as cloud condensation nuclei. Previously, modeling studies have shown that higher aerosol concentrations lead to aerosol-induced invigoration of deep convective storms. (In this study, we define invigoration as an increase in cloud updraft speed.) We seek to evaluate the effects of increased aerosol concentrations on observed updraft speeds in a statistically robust way. This study uses GOES16 geostationary satellite data to track more than 100 isolated, developing, deep convective clouds over the Southern Great Plains region in Oklahoma. Since updraft speeds cannot be measured directly by satellites, we assume updraft speeds to be proportional to the cloud top rise rate. First, we correlate the rise rates with environmental properties including CAPE, tropospheric relative humidity, and shear. We find these properties are very strongly correlated with the rise rates only when the isolated storms are at least ~50 miles from any other deep convection. When other convection is located more closely, these correlations become substantially weaker. Next, we use the environment’s relationship with cloud top rise rates to control for the meteorology and then correlate the rise rates with surface aerosol concentrations from the ARM SGP site. We currently find no relationship between aerosol concentration and updraft speed. We are working to extend the methodology to other regions where aerosol impacts on rise rates, should such impacts exist, may be more detectable.