ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-11-8415-2011 The fate of saharan dust across the atlantic and implications for a central american dust barrier Nowottnick E. 1 Colarco P. 2 da Silva A. 3 Hlavka D. 4 McGill M. 5 Atmospheric and Oceanic Sciences, University of Maryland, College Park, MD, USA Atmospheric Chemistry and Dynamics Branch, Code 613.3, NASA Goddard Space Flight Center, Greenbelt, MD, USA Global Modeling and Assimilation Office, Code 610.1, NASA Goddard Space Flight Center, Greenbelt, MD, USA Science Systems and Applications, Inc., Code 613.1, NASA Goddard Space Flight Center, Greenbelt, MD, USA Mesoscale Atmospheric Process Branch, Code 613.1, NASA Goddard Space Flight Center, Greenbelt, MD, USA 18 08 2011 11 16 8415 8431 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/11/8415/2011/acp-11-8415-2011.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/8415/2011/acp-11-8415-2011.pdf

Saharan dust was observed over the Caribbean basin during the summer 2007 NASA Tropical Composition, Cloud, and Climate Coupling (TC<sup>4</sup>) field experiment. Airborne Cloud Physics Lidar (CPL) and satellite observations from MODIS suggest a barrier to dust transport across Central America into the eastern Pacific. We use the NASA GEOS-5 atmospheric transport model with online aerosol tracers to perform simulations of the TC<sup>4</sup> time period in order to understand the nature of this barrier. Our simulations are driven by the Modern Era Retrospective-Analysis for Research and Applications (MERRA) meteorological analyses. Compared to observations from MODIS and CALIOP, GEOS-5 reproduces the observed location and magnitude of observed dust events, but our baseline simulation does not develop as strong a barrier to dust transport across Central America as observations suggest. Analysis of the dust transport dynamics and loss processes suggest that while both mechanisms play a role in defining the dust transport barrier, loss processes by wet removal of dust are about twice as important as transport. Sensitivity analyses with our model showed that the dust barrier would not exist without convective scavenging over the Caribbean. The best agreement between our model and the observations was obtained when dust wet removal was parameterized to be more aggressive, treating the dust as we do hydrophilic aerosols.

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