乌兰布和沙漠东北缘防护林内外沙尘暴低空结构特征

Low-Altitude Structure of Sandstorms for Inside and Outside the Shelterbelt in the Northeast Marginal Zone of the Ulan Buh Desert

基于内蒙古磴口荒漠生态系统国家定位观测研究站近地层(050m)风沙监测塔所收集的8次沙尘暴的沙尘水平通量、垂直通量和风速风向数据,对乌兰布和沙漠东北缘中小尺度条件下的防护林内外沙尘暴过程中风况变化、沙尘分布特征以及防护林对沙尘暴的影响进行研究。结果表明:①沙尘暴发生过程中,防护林内外风速均随高度增加呈现递增趋势,风速廓线特征遵循幂函数,防护林内外均以W、WNW、NE方向为主,但每个方向所占比例不同。②防护林外沙尘水平通量及沙尘浓度随高度增高显著减小,其垂直分布特征均符合指数函数关系;防护林内沙尘水平通量及沙尘浓度则随着高度增高缓慢上升,其垂直分布特征均符合幂函数关系。沙尘垂直通量则均随着高度的增高明显减小,其垂直分布特征均符合幂函数关系。③沙尘暴经过防护林体系时,风速显著削弱,平均消减31.03%;沙尘水平通量降低298.16g·m^-2,垂直通量降低0.37g·m^-2,沙尘浓度降低22.48g·m^-2。

In this paper,the data of horizontal and vertical sand-dust flux and the annual wind speed and direction during eight sandstorms,collected from the sandwatch tower near the surface layer (0-50 cm) of Inner Mongolia Dengkou Desert Ecosystem National Observation Research Station,were used. The purposes of the study were to analyze the variations of sand-driving wind regime,distribution of wind-blowing sand and the effect of shelterbelt on sandstorms on small scale in the northeast marginal zone of the Ulan Buh Desert. The results were as follows:① The average wind speed inside and outside the shelterbelt increased with the increase of height,the wind speed profiles during sandstorms could be expressed by the power exponential function,the prevailing wind directions inside and outside the shelterbelt were W,WNW and NE,but their proportions were different.② The horizontal wind-blowing sand flux and the sand-dust concentration outside the shelterbelt decreased with the increase of height. The distribution of wind-blowing sand accorded with the exponential function,the horizontal wind-blowing sand flux and sanddust concentration inside and outside the shelterbelt increased slowly with the increase of height,and the distribution of wind-blowing sand accorded with the power exponential function. The vertical wind-blowing sand flux inside and outside the shelterbelt decreased significantly with the increase of height,and the distribution of wind-blowing sand accorded with the power exponential function.③ When sandstorm passed through the shelterbelt system,the wind speed was significantly decreased with an average reduction of 31. 03%,while the horizontal and vertical fluxes of wind-blowing sand were reduced by 298. 16 g·m^-2 and 0. 37 g·m^-2 respectively,and the concentration of windblowing sand was decreased by 22. 48 g·m^-2.