Influence of Saharan Dust on the Large‐Scale Meteorological Environment for Development of Tropical Cyclone Over North Atlantic Ocean Basin

Abstract

AbstractThe tropical cyclones (TCs) frequently occur in the North Atlantic Ocean Basin, which is adjacent to West Africa, the largest global source of atmospheric dust. However, few studies have conducted systematic observational research of how dust affects the genesis conditions of TCs at large scales which includes sea surface temperature (SST), vorticity, vertical wind shear, and specific humidity. This study focused on the period from June–September in the years 2000 to 2018 to investigate the horizontal and vertical distributions of aerosol optical depth (AOD) (dust) and meteorological parameters. Dust can be transported at 600 hPa upward and is mixed well within the troposphere over land, while it is mainly distributed in the lower troposphere over the ocean. The SST is significantly suppressed by dust due to direct radiation effects, but the atmospheric temperature is warmer at 20–40°W between 700 and 850 hPa. The vertical distributions of temperature and specific humidity are similar. Dust decreases specific humidity in the lower troposphere over the ocean, especially in high AOD regions, but enhances midlevel moisture. Dust heats the lower troposphere and favors the development of convection and positive vorticity at heights of approximately 800–1,000 hPa. The warming effect of dust on the lower atmosphere over land and the nearby oceans results in strengthened West African monsoons and vertical wind shear. Thus, dust suppresses the SST and low‐level specific humidities and favors wind shear and positive relative vorticity, which further influence environmental conditions in the TC genesis region.