Estimation of the Threshold Friction Velocities over Various Dust Storm Source Areas in Northwest China

The emission of dust particles into the atmosphere is governed by the aerodynamic and resistant factors which are quantified by the friction velocity v and the threshold friction velocity mu.iota, respectively The threshold friction velocity u.iota influences the Vertical dust flux and dust transport. Based on the micrometeorological data obtained in the springs of 2004 and 2006 over Hunshandake desert area Loess Plateau, and Gobi desert area the relationship between dust. concentration and friction velocity for the dust. events that occurred over Hunshandake desert area was investigated and the threshold friction velocities over the three different. dust source areas were estimated The results show that the value of dust, concentration is low during the pre emission stage of a dust storm event and the rapid increase of friction velocity provides favorable dynamic conditions for dust emission During the dust emission stage, the dust concentration increases sharply due to mechanical and thermal turbulent mixing At the calm down stage the dust concentration drops nearly linearly with the decreasing friction velocity on account of the gravitational deposition of larger dust particles When the dust concentration is higher than 200 mu g m(-3), it is considered as a dust emission process According to the criteria, the allies of threshold friction velocity over Hunshandake desert area and Gobi region are 0 6 and 0 45 ins respectively The threshold friction velocity over Loess Plateau depends on the wind direction, due to the complex terrain and in homogeneous surface The northwest wind shows the effects of the Mu Us desert in the northwest The corresponding u.iota is 0 35 m s(-1) The south wind exhibits the characteristics of the Loess hilly dunes in the south and the u iota is 0 7 m s(-1) The large roughness length of the Loess hilly dunes and the large inter particle cohesion for the clay soil texture increases the local friction velocity Different threshold friction velocities and occurrence frequencies of strong Wind account for different dust, emission capabilities for various source areasMeteorology & Atmospheric SciencesSCI(E)中文核心期刊要目总览(PKU)中国科技核心期刊(ISTIC)6ARTICLE5548-5572