Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 8 23 2008 10.5194/acp-8-6979-2008 http://www.atmos-chem-phys.net/8/6979/2008/ http://www.atmos-chem-phys.net/8/6979/2008/acp-8-6979-2008.html http://www.atmos-chem-phys.net/8/6979/2008/acp-8-6979-2008.pdf 6979 6993 2008-12-04 Observations of mesoscale and boundary-layer scale circulations affecting dust transport and uplift over the Sahara J. H. Marsham jmarsham@env.leeds.ac.uk D. J. Parker C. M. Grams B. T. Johnson W. M. F. Grey A. N. Ross University of Leeds, UK Universität Karlsruhe and Forschungszentrum Karlsruhe, Germany Climate and Land Surface Systems Interaction Centre, School of the Environment and Society, Swansea, SA2 8PP, UK The Met Office, UK Observations of the Saharan boundary layer, made during the GERBILS field campaign, show that mesoscale land surface temperature variations (which were related to albedo variations) induced mesoscale circulations. With weak winds along the aircraft track, land surface temperature anomalies with scales of greater than 10 km are shown to significantly affect boundary-layer temperatures and winds. Such anomalies are expected to affect the vertical mixing of the dusty and weakly stratified Saharan Residual Layer (SRL). Mesoscale variations in winds are also shown to affect dust loadings in the boundary layer. <br><br> Using the aircraft observations and data from the COSMO model, a region of local dust uplift, with strong along-track winds, was identified in one low-level flight. Large eddy model (LEM) simulations based on this location showed linearly organised boundary-layer convection. Calculating dust uplift rates from the LEM wind field showed that the boundary-layer convection increased uplift by approximately 30%, compared with the uplift rate calculated neglecting the convection. 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