Summertime Taklimakan dust structure

Vertical dust structures and meteorological conditions over the Taklimakan Desert during the summertime periods (July-September) in 2006 and 2007 were investigated using satellite data including the CALIPSO lidar (CALIOP) measurements and the Weather Research and Forecasting (WRF) model simulation. Summertime convective velocity simulated by WRF was greater than 3 m/s, and the convective time scale was about 1000 s (ca. 15 min). We examined 42 CALIPSO paths (24 daytime and 18 nighttime paths) of data acquired under convective dusty conditions. The dust layer thickness derived from the CALIOP measurements reaches 3000-4000 m, which is approximately equal to the Tarim Basin depth. This thickness shows a good correlation with the WRF simulated depth of the convective boundary layer (BL). The dust remains suspended during both daytime and nighttime; the CALIOP average dust extinction coefficients in the BL are respectively 0.151 +/- 0.102 km(-1) and 0.128 +/- 0.079 km(-1) for daytime and nighttime. Finally, we estimated the dust amount transported from the BL to the free atmosphere. Typically, 10-20 Gg/day of dust (assuming area of 600 km x 300 km as a main part of the Taklimakan Desert) is transported from the Taklimakan Desert by vertical mixing. The daily horizontal dust flux above the BL was estimated to be 40-50 Gg/day over the Taklimakan Desert.