Examining the Relationship Between Tropical Cyclones and African Dust Using the Community Atmosphere Model

With advanced high-resolution atmospheric modeling, it is becoming possible to explore the impacts of African dust on the formation of tropical cyclones (TCs) in the North Atlantic Ocean.  The Community Atmosphere Model (CAM) in two different aerosol model configurations (i.e., prescribed and prognostic aerosol formulations) forced by observed sea surface temperatures and greenhouse gas concentrations is used to investigate the potential role that African dusts plays on the region’s environment and how this impacts TC activity. Previous work has shown that high-resolution CAM simulations with a grid spacing of approximately 25 km are more capable of resolving many important TC features (e.g., storm intensity and regions of formation) globally compared to conventional climate simulations with a grid spacing of about 100 km. The high-resolution CAM simulations used here are evaluated by comparison to observational datasets, including the Advanced Very High Resolution Radiometer (AVHRR), Climate Forecast System Reanalysis (CFSR), and Modern-Era Retrospective Analysis for Research and Applications Version 2(MERRA-2). Various analysis domains are used, such as the main development region for TCs in the North Atlantic, to see how different regions affect the correlation between African dust, tropical cyclones, and the background environment. In observations of the main development region, aerosol optical depth is negatively correlated with TC counts at the 95% confidence level, while the two model configurations differ in this regard. The prescribed configuration has only a slight negative correlation, however the prognostic configuration has a negative correlation at about the 90% confidence level. This result may shed light on the difference in skill of the two model simulations to capture the observed interannual variability of TC counts in the North Atlantic region.