Simulating Direct Effects of Dust Aerosol on Arid and Semi-arid Regions Using an Aerosol–Climate Coupled System

This study used an aerosol–climate coupled system BCC_AGCM2.0.1_CUACE to investigate the direct climatic effects of dust aerosol on global arid (including hyper-arid) and semi-arid regions. Results show that dust aerosol can cause surface cooling over these regions. The cooling effects, however, are stronger in the Northern Hemisphere (NH) than the Southern Hemisphere (SH). This asymmetric cooling forces a thermal meridional circulation between 30°S and 30°N, with air descending (ascending) in the NH (SH), leading to a decrease (increase) in precipitation in the arid and semi-arid regions over the NH (SH). Dust aerosol can decrease the potential evapotranspiration in arid and semi-arid regions mainly by decreasing the net radiation flux at the top of the atmosphere, which compensates for the decrease in precipitation. Therefore, as the dominant aerosol in the arid and semi-arid regions, dust aerosol does not exacerbate the aridity over most of these regions. The effects of dust aerosol are indiscernible in the expansion of arid and semi-arid areas on a global scale.