Analysis of a Trans-Atlantic Saharan Dust Outbreak Based on Satellite and GATE Data

Abstract

We present the evolving fields of a Saharan dust outbreak and its associated air mass, as the outbreak and the air mass moved across the Atlantic over a nine-day period. New details are revealed from high-resolution satellite measurements and ship soundings from GATE [Global Atmospheric Research Program (GARP) Atlantic Tropical Experiment]. A McIDAS (Man Computer Interactive Data Access System) turbidity analysis was produced for each day following dust exit from the African coast. The digital fields are subjected to local space and time continuity checks in order to minimize contamination from small clouds and other error sources. Quantitative turbidity fields show the systematic spreading of the dusty air, its gradual depletion, and its relation to synoptic cloud systems. A clearer picture of the changing structure of the elevated Saharan air lens is made possible by the GATE analyses. High-resolution thermodynamic analyses in vertical planes and the time domain demonstrate the sharp southern boundary and detailed variations in passage across the ocean. Taken together with wind data, the results show the transit of dust and air mass together across the Atlantic, with an unsteady relation to the adjacent easterly wave circulations.