Transport of Saharan dust over the Caribbean Islands: Study of an event

Abstract

A dust plume transported across the Atlantic Ocean from West Africa to Guadeloupe in June 1994 is studied using several complementary and cross-checking techniques. During this event the dust optical depth measured in Guadeloupe was high from 19 to 22 June, peaking at 1. Meteosat-5 IR imagery is used to locate in SW Sahara the source of emitted dust, consistent with the simulated backward trajectories of the dusty air masses arriving over Guadeloupe. Meteosat-3 visible light spectrometer (VIS) imagery over the north tropical Atlantic shows the dust plume leaving the Affican coast on 15 June and its subsequent spreading over ocean on the following days. The back trajectories indicate a strong uplift from the African source to an altitude of 5000 in on 14 and 15 June, followed by a subsiding motion of the dust plume from the African coast to Guadeloupe, in agreement with the meteorological soundings performed at east and west sides of the Atlantic Ocean. Such uplifts, observed during summer, are shown to be a condition for the long-range transport of dust through the Atlantic. It is also observed that while dust transport is associated with the dynamics of the Saharan air layer, the latter can be dust free. The transported mass of dust was in the range 2.5-5 Mt for this event. Electronic microscopy applied to the mineral particles collected in rainwater just after the dust event shows the predominance of particles larger than 1 μm in the long-range transport from Africa. Copyright 2005 by the American Geophysical Union.