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Journal Article: BibTeX citation key:  Knippertz2007a
Knippertz, P., Deutscher, C., Kandler, K., Müller, T., Schulz, O. & Schütz, L. (2007) Dust mobilization due to density currents in the Atlas region: Observations from the Saharan Mineral Dust Experiment 2006 field campaign. IN Journal of Geophysical Research - Atmospheres, 112. D21109.
Added by: Peter Knippertz 2010-08-20 13:46:53    Last Edited by: Fanny Lefebvre 2011-01-17 17:43:05
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Categories: Atmospheric processes
Keywords: Aerosol, Atmospheric Boundary Layer, Clouds - Convection, Diurnal cycle, Dynamics, Precipitation, Rainfall, Semi-arid
Creators: Deutscher, Kandler, Knippertz, Müller, Schütz, Schulz
Collection: Journal of Geophysical Research - Atmospheres

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Abstract
Evaporation of precipitation is a ubiquitous feature of dry and hot desert environments. The resulting cooling often generates density currents with strong turbulent winds along their leading edges, which can mobilize large amounts of dust. Mountains support this process by triggering convection, by downslope acceleration of the cool air, and by fostering the accumulation of fine-grained sediments along their foothills through the action of water. For the Sahara, the world's largest dust source, this mechanism has been little studied because of the lack of sufficiently high resolution observational data. The present study demonstrates the frequent occurrence of density currents along the Sahara side of the Atlas Mountain chain in southern Morocco using the unique data set collected during the Saharan Mineral Dust Experiment (SAMUM) field campaign in May/June 2006. The density currents are related to convection over the mountains in the afternoon hours and have lifetimes on the order of 10 h. The passage of the sharp leading edge that sometimes reaches several hundred kilometers in length is usually associated with a marked increase in dew point and wind speed, a change in wind direction, and a decrease in temperature and visibility due to suspended dust. It is conceivable that this mechanism is relevant for other mountainous regions in northern Africa during the warm season. This would imply that simulations of the dust cycle with numerical models need a reliable representation of moist convective processes in order to generate realistic dust emissions from the Sahara.
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Added by: Fanny Lefebvre    Last Edited by: Fanny Lefebvre