Radiative feedback of dust aerosols on the East Asian dust storms

摘要

A new radiative parameterization scheme of dust aerosol has been developed within amesoscale dust storm (DS) forecasting model to study the direct radiation of dustaerosol by incorporating both online forecasted dust concentrations and the updated dustreflective index. The radiation-induced temperature variations are fed back online to themodel dynamics, resulting in two-way interactions between meteorology and dustaerosols. For a typical DS of 16-18 April 2006 in East Asia, the study shows that thestrong extinction by dust leads to significant changes in the radiation flux from surface tothe top of atmosphere, which tends to decrease the air temperature in the lower dust aerosollayers but to increase the air temperature in the upper dust aerosol layers. Consequently,variations of 3-D temperature fields reduce the cold air in the upper atmosphere, increasethe sea level air pressure, decrease surface wind velocity, and eventually weaken theMongolian cyclones owing to the blocking effects. These changes, in return, have impactson the emission, transport, and deposition processes of DS. The interactively simulated totaldust emission from the ground is reduced by over 50%, and the 72-hour averagedoptical depth of dust aerosols declines by about 33% compared to the one-way modelwithout dust direct radiative feedback, which indicates strong negative feedback effects.The findings of this study also suggest that online calculation of dust direct radiative effectsin a mesoscale dust prediction model may lead to an improvement in the prediction ofmeteorological elements such as temperature, wind, and pressure during the dust eventsowing to its improved calculation accuracy of regional radiation budgets.