Suppression of deep convection over the tropical North Atlantic by the Saharan Air Layer

The effects of the dust-laden Saharan Air Layer ( SAL) on the occurrence of deep convection over the eastern and central tropical North Atlantic Ocean off-shore of the African continent during August - September 2002 are investigated. We show that the SAL is associated with suppressed convection in this region. To determine the possible cause of the suppressed convection, the thermodynamic structure and dust content of the SAL are investigated. We find that the SAL is associated with warmer and dryer air below 700 hPa with the largest temperature anomalies located around 850 hPa. This warm and dry air layer raises the lifting condensation level and level of free convection, and increases the energetic barrier to convection that leads to reduced occurrence of deep convection.