干旱区生态环境知识资源中心

The joint Japan-Mongolia-USA project DUVEX (Dust-Vegetation Interaction Experiment) was designed to develop a biogeophysical model which can simulate dust emission and eco-system processes over the vegetated land surface. Dust emission processes have been investigated mostly on bare land, and there is very little information about vegetated land. Thus, intensive observations were conducted of a dust event that occurred on the Mongolian steppe on 24 April 2008.

Meteorological and dust elements (e. g., saltation flux, visibility, dust concentration) and land-surface parameters (e. g., roughness length, vegetation cover, and the ground-based normalized difference vegetation index) were measured. During the event (from 13: 00 to 18: 00 LST on 24 April), the threshold wind speed at 1.54 m height, which is the minimum wind speed inducing saltation of particles ranging from 30 to 667 mu m in diameter, was 8.9 m s(-1) on a land surface with 7.2% vegetation cover with dead brown leaves, a small roughness length (0.0058 m), and a very dry sandy soil at 0-5 mm depth (water content, 0.002 g g(-1)). For comparison with previous studies, the threshold wind speed value was converted to the values at the heights in each study by using the logarithmic law of wind profile. Our value is close to the SYNOP-derived values for the same area, but larger than ground-observed and SYNOP-derived values for East Asian deserts.