Composite analysis of dust impacts on African easterly waves in the Moderate Resolution Imaging Spectrometer era

This study examines the synoptic scale impacts of African dust on easterly waves in the tropical northeast Atlantic. Moderate Resolution Imaging Spectrometer aerosol optical depth (AOD), National Oceanic and Atmospheric Administration products, and National Center for Environmental Prediction reanalysis fields in the Atlantic main hurricane development region (MDR) form the basis for statistical analysis of a limited set of cases objectively selected for the 2000–2008 hurricane seasons when thresholds are exceeded for sea surface temperature (SST), easterly wind shear, cyclonic vorticity, and upward motion. After ranking African easterly waves by AOD, the top (dusty) and bottom (clean) cases are studied as composite differences. African dust and subsidence cause temperatures to warm ∼3°C in the 700 hPa layer, while SSTs cause temperatures to cool, stabilizing the atmosphere. Increased AOD and strong (10 m s −1 ) 600 hPa easterly winds limit cloud efficiency through shear and oversupply of condensation nuclei. Vertical section composites demonstrate that warm dry subsident air coincides with the African dust plume in the latitudes 18°N–30°N. Hurricane reanalysis data indicate that higher AOD in the MDR reduces chances for the intensification of African easterly waves.