Impacts of mineral dust on the vertical structure of precipitation

Abstract

Characteristics of precipitation vertical structure in deep convective cloud systems are compared using measurements from sensors on board multiple satellites over the equatorial Atlantic under dust-laden and dust-free conditions. Both case and statistical studies consistently show that the impacts of mineral dust on tropical cloud and precipitation systems are highly dependent on rain type. For convective rain, the pattern of rainfall profiles above the dust layer is mainly determined by updraft intensity. For similar updraft intensity, the convective rain at and below the dust layer exhibits enhancement of the breakup process of raindrops due to mineral dust and associated warm air with strong wind shear. For stratiform rain, dust-induced microphysical effects are more evident. For similar storm height (or the rain top), precipitation at altitudes above 6 km is enhanced under dust-laden conditions, suggesting an enhancement of ice heterogeneous nucleation. For warm rain with similar storm height, precipitation is systematically weaker under dust-laden conditions. Furthermore, the ratio of precipitation water to the total amount of atmospheric hydrometeors is smaller under dust-laden conditions. Our study suggests that mineral dust exhibits a second aerosol indirect effect on cloud and precipitation systems. Copyright © 2010 by the American Geophysical Union.