A retrospective study of the Interaction of the Saharan Air Layer with Atlantic basin tropical cyclones

The ability to monitor Saharan Air Layers (SALs) with multispectral Geostationary Operational Environmental Satellite (GOES) infrared imagery is only several years old (Dunion and Velden, 2004). However, this current study determined that the relativey low humidity values present in SALs were also reflected in the SSM/I derived quantity of total precipitable water. These estimates which reliably date back to 1987, have provided sufficient “SAL signatures” to attempt a retrospective analysis of the SAL and its interaction with historical Atlantic tropical cyclones. This research establishes the water vapor characteristics of SALs from several relatively recent known SAL events, and then presents representative cases of several older storms that may have been affected by this type of interaction. In some cases, when SALs were prominent in the eastern North Atlantic (e.g. 1997 [also an el Nino year]) there were relatively few storms that originated in the Cape Verde region. Findings from this study can be used to increase our understanding of tropical cyclogenesis, under performing tropical cyclones and the rapid intensification that sometimes occurs when a storm that has been embedded in a SAL emerges from its influence.