Trajectories for Saharan Dust Transported to Barbados Using Stokes's Law to Describe Gravitational Settling

Abstract Atmospheric chemistry programs often make use of retrospective back trajectories to determine the source regions of substances sampled at a particular site. Isentropic trajectories, which depict motion on hypothetical surfaces of constant potential temperature, have been used as part of the Atmosphere/Ocean Chemistry Experiment to understand the sources of aerosols and gases sampled over the North Atlantic Ocean. However, isentropic trajectories typically do not adequately describe the transport of mineral aerosol, for example, from the Sahara Desert to Barbados. Boundary layer trajectories indicated that northern Africa was the source region for 12% of the samples with significant aluminum (Al) concentrations (> 1.0 µg m−3). Upper-level isentropic trajectories (310 and 315 K) indicated transport from northern Africa for approximately half of the samples with Al concentrations greater than 1.0 µg m−3. However, at the location of the sampling site, the upper-level trajectories were well above the ...