Characterization of the Saharan Air Layer with a Combination of Decade-long Aerosol Reanalysis, Satellite Products and In Situ Observations

The Saharan Air Layer (SAL) is an elevated airmass of hot and dry conditions that influences the large-scale environment over the tropical north Atlantic and the Caribbean basins. Often it carries large amounts of airborne dust, which is thus often used as an indicator of SAL in the literature. The SAL is still a subject of ongoing study and research; however its definition is vague and varies among researchers. The emergence of a decade-long aerosol reanalysis dataset, the Navy Aerosol Analysis and Prediction System (NAAPS) Aerosol Optical Thickness (AOT) reanalysis, enables quick identification of dust-laden SAL events. It utilizes a modified NAAPS at its core and assimilates quality controlled retrievals of AOT from the Moderate Resolution Imaging Spectroradiometer (MODIS) on Terra and Aqua and the Multi-angle Imaging SpectroRadiometer (MISR) on Terra. Along with satellite-retrieved total precipitable water product, meteorological reanalysis (ERA-interim) and Caribbean region sounding observations (WMO sites), we reconcile the airborne dust and physical meteorological views of the SAL. The two methods of defining SAL events, one based on aerosol features and the other on thermodynamics, are compared in the context of meteorological and aerosol environments. To what extent dust aerosol can be used as an indicator of a SAL event, is discussed. These results have implications for the study of the SAL and its potential impacts on other meteorological and climate phenomena, such as tropical cyclones.