In support of western Africa coast Saharan Air Layer (SAL) studies, the Naval Research Laboratory in Monterey CA (NRLMRY) provides daily MODIS-derived aerosol optical depth (AOD) products in near real time throughout tropical latitudes (0N – 30N) of the Atlantic Basin. The products are produced from a basic radiative transfer equation developed at the Naval Postgraduate School (NPS-AOD) that ingests and processes radiances from MODIS channels 1 (visible) and 2 (near-IR). The NPS-AOD applies linearized single scatter theory with a bi-directional surface reflectance, and assumes that aerosols are single scatter, non-absorbing, and spherical. The algorithm has performed adequately over fairly pristine conditions such as those encountered during TARFOX, ACE-1 and 2 field experiments. AERONET stations over Cape Verde and Praia only provide a limited scope of support.

To assist with this process, NRL has recently installed and is producing “Deep Blue”, a land-only AOD algorithm developed at the NASA Goddard Space Flight Center (GSFC). Unlike other land AOD algorithms, Deep Blue provides data over the brightly reflective surface within the Saharan Desert, the source of SAL outbreaks. Deep Blue has been validated over ACE-Asia and UAE² field experiments. The dust flowing off the coast aids in the quantitative assessment of AOD which can then be applied to the NPS algorithm over water. This interaction assists in the improved accuracy of AOD values as the dust events propagate across the Atlantic Basin.

This paper focuses on the aerosol study during SAL episodes over the Atlantic Basin during the summer months of 2008. Deep Blue and NPS relative AOD values are traced from source regions within the Saharan Desert and over the Atlantic Basin into the Caribbean and US east coast. The AERONET stations situated over Cape Verde, Praia, and Banizoumbou as well as the western AERONET station at La Paguera and Roosevelt Roads in Puerto Rico, and Key Biscayne and Crystal Face in Florida. Part of this study is to view the evolution of SAL with impacts on tropical cyclone interactions.