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 degrees N, 6.9 degrees 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).
|Number of pages||14|
|Journal||Tellus Series B-Chemical and Physical Meteorology|
|Publication status||Published - Feb 2009|
- AUSTRALIAN LANDSCAPE