Vertical profiling of convective dust plumes in southern Morocco during SAMUM

Authors: ANSMANN, ALBERT; TESCHE, MATTHIAS¹; KNIPPERTZ, PETER²; BIERWIRTH, EIKE²; ALTHAUSEN, DIETRICH¹; MÜLLER, DETLEF¹; SCHULZ, OLIVER³

Source: Tellus B, Volume 61, Number 1, February 2009 , pp. 340-353(14)

Publisher: Wiley-Blackwell

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Abstract:

Lifting of dust particles by dust devils and convective plumes may significantly contribute to the global mineral dust budget. During the Saharan Mineral Dust Experiment (SAMUM) in May-June 2006 vertical profiling of dusty plumes was performed for the first time. Polarization lidar observations taken at Ouarzazate (30.9°N, 6.9°W, 1133 m height above sea level) are analyzed. Two cases with typical and vigorous formation of convective plumes and statistical results of 5 d are discussed. The majority of observed convective plumes have diameters on order of 100-400 m. Most of the plumes (typically 50-95%) show top heights <1 km or 0.3DLH with the Saharan dust layer height DLH of typically 3-4 km. Height-to-diameter ratio is mostly 2-10. Maximum plume top height ranges from 1.1 to 2.9 km on the 5 d. 5-26 isolated plumes and clusters of plumes per hour were detected. A low dust optical depth (<0.3) favours plume evolution. Observed surface, 1 and 2-m air temperatures indicate that a difference of 17-20 K between surface and 2-m air temperature and of 0.9-1 K between the 1 and 2-m temperatures are required before convective plumes develop. Favourable horizontal wind speeds are 2-7 m s⁻¹.

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1600-0889.2008.00384.x

Affiliations: 1: Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany 2: Institute for Atmospheric Physics, Johannes Gutenberg University, Becherweg 21, 55099 Mainz, Germany 3: Department of Geography, University of Bonn, Meckenheimer Allee 166, 53115 Bonn, Germany

Publication date: 2009-02-01