Saharan air layer

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Saharan air layer

(Abbreviated SAL.) A hot, dry, and often dusty layer in the lower troposphere that, over the Atlantic Ocean, generally overlies cooler, more humid marine boundary layer air. It originates from a deep, dry convective boundary layer over the Saharan region of northern Africa where it is characterized by well-mixed vertical profiles of potential temperature and water vapor mixing ratio from near the surface to ~5–6 km altitude. It is also frequently associated with a deep layer of dust. This layer is periodically advected westward off the African continent by subtropical easterly flow and can occasionally reach the Caribbean and eastern North America, with peak activity occurring in July. Over the Atlantic Ocean, the SAL is characterized by very warm and dry conditions in its lower part and cooler and moister conditions in its upper part relative to typical subtropical oceanic conditions, with a strong temperature inversion at its base above the marine boundary layer.“

Braun, S. A., 2010: Reevaluating the role of the Saharan air layer in Atlantic tropical cyclogenesis and evolution. Mon. Wea. Rev., 138, 2007–2037, doi:10.1175/2009MWR3135.1.

Term edited 17 January 2021.

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