Observations of an 11 September Sahelian Squall Line and Saharan Air Layer Outbreak during NAMMA-06

Abstract

The 2006 NASA-African Monsoon Multidisciplinary Analyses (NAMMA-06) field campaign examined a compact, low-level vortex embedded in the trough of an AEW between 9–12 September. The vortex triggered a squall line (SL) in southeastern Senegal in the early morning of 11 September and became Tropical Depression 8 on 12 September. During this period, there was a Saharan Air Layer (SAL) outbreak in northwestern Senegal and adjacent Atlantic Ocean waters in the proximity of the SL. Increases in aerosol optical thicknesses in Mbour, Senegal, high dewpoint depressions observed in the Kawsara and Dakar rawinsondes, and model back-trajectories suggest the SAL exists. The close proximity of this and SL suggests interaction through dust entrainment and precipitation invigoration.