Impacts of Saharan Dust on Regional Climate and Tropical Cyclogenesis over the Atlantic Basin

Saharan dust can exert substantial radiative and microphysical effects on the regional climate system. Its impacts on the genesis and intensification of tropical cyclones (TCs) remain unclear. In this research, the influences of Saharan dust on the Atlantic regional climate and the genesis of TCs are investigated in the hurricane seasons of 2005 and 2006, which represent the active and inactive hurricane seasons respectively. The atmospheric stand-alone version of the Community Earth System Model version 1.0.4 (CESM1.0.4), CAM5.1, is used to simulate the climate condition in full (dust) and none dust (non-dust) scenarios. Two regions of interest, the Atlantic TC genesis region (GNR, 50W-20W, 5N-15N) and the TC intensification region (ITR, 70W-40W, 15N-30N), are defined by Lau and Kim [2007] and are investigated. Model output proves the important impacts of the Saharan dust on the radiative budget, hydrological cycle, and TC genesis. The dust perturbs the large-scale circulation that moves the ITCZ northward, enhances the West African monsoon, changes the cloud fraction, and perturbs the regional longwave and shortwave radiations. Dust favors the genesis of TCs thermodynamically by increasing the mid-level moisture in the GNR but suppresses the TC formation by increasing the vertical wind shear and decreasing low-level vorticity in the GNR. It is likely that the TC genesis region shifts northward with the ITCZ.