Simulating direct effects of dust aerosol on arid and semi‐arid regions using an aerosol–climate coupled system

Abstract

ABSTRACTThis work uses an aerosol–climate coupled system to study 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 of dust aerosol are larger in the Northern Hemisphere (NH) than in the Southern Hemisphere (SH). This asymmetric cooling leads to a severer reduction in evaporation over the low latitudes of the NH compared with their counterpart areas in the SH. In addition, air descent is enhanced (or ascent is weakened) by dust aerosol over the low latitudes of the NH, whereas the reverse happens in the SH. With the anomalous in evaporation and circulation, precipitation is decreased (increased) over the arid and semi‐arid areas in the NH (SH) by dust aerosol. 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 caused by dust aerosol. 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.