Effects of Dust Layers on Trade Wind Cumuli Over the Gulf of Mexico

The understanding of the indirect effects on trade cumuli is arguably the poorest of all cloud types. One uncertainty in quantifying the indirect effect of aerosols is quantifying how aerosols within the Saharan air layer (SAL) affect the properties of trade wind cumuli either by acting as cloud condensation nuclei (CCN) or by altering radiative heating due to the absorption and scattering of solar radiation. The impact of the SAL on cumuli over the Gulf of Mexico was investigated using the three-dimensional non- hydrostatic Eulerian and semi-Lagrangian (EULAG) anelastic model initialized with and evaluated against measurements obtained during the Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS). A recently developed double moment warm rain microphysical scheme has been incorporated into the model to treat the droplet activation. The competing effects of aerosols on the SAL through their role in redistribution of vertical profiles of heating and acting as condensation nuclei will be addressed.