Modeling Arabian dust mobilization during the Asian summer monsoon: The effect of prescribed versus calculated SST

Abstract

Emission of soil (or 'mineral') dust aerosol over the Arabian Peninsula during the Northern Hemisphere (NH) summer monsoon increases in response to dust radiative forcing in an atmospheric general circulation model (AGCM) with prescribed sea surface temperature (SST). Radiative heating within the dust layer reinforces the monsoon circulation, which is further strengthened by column latent heating through a wind-evaporative feedback. The strengthened circulation raises additional dust into the atmosphere over Arabia. In contrast, this positive feedback is absent when SST is calculated by the AGCM using a mixed-layer ocean. This discrepancy results from the surface energy constraint in the mixed-layer experiment, where surface evaporation is decreased by the reduction of sunlight beneath the dust layer. In contrast, evaporation and column latent heating increase in the prescribed SST experiment, where the surface energy constraint is absent. Realization of the positive feedback exhibited by the prescribed SST experiment requires that anomalous ocean heat transport (which is not included here) balance the surface radiative forcing by dust. Copyright 2004 by the American Geophysical Union.