内蒙古草原近地层垂直风速廓线的观测研究

Observational study of the vertical wind profile in the Inner Mongolia grassland near-surface

利用中国国家气候中心2009-2010年在内蒙古锡林浩特开展的100 m铁塔大气湍流观测数据,分析了不同稳定度条件下的垂直风廓线变化特征,并在局地相似理论基础上建立了垂直风廓线表达式。结果表明:(1)内蒙古草原近地层大气中,不稳定层结和稳定层结条件发生的概率远高于中性和弱不稳定、弱稳定层结的发生概率。(2)稳定层结时,大气特性在垂直方向上变化较明显,需要按照不同的高度层分别研究其风速的变化规律。根据内蒙古锡林浩特草原大气湍流观测资料得到,稳定层结时的无因次风速梯度随稳定度ξ的变化关系可以表达为1+β_mξ,其中β_m的取值与距地面高度有关:30 m高度及以下,β_m取4.3-5.4;高度在(30 m,50 m],β_m取2.9-3.4;50 m及以上高度,β_m取2.0-2.9。

Using the 100 m tower atmospheric turbulence observation experiment data during 2009 - 2010 in Inner Mongolia of- fered by the National Climate Center, the variation characteristics of vertical profile of wind speed under the different stability conditions are analysed, and the wind profile expression is established based on the local similarity theory. The results show that： （1） In the Inner Mongolia grassland near surface atmosphere, the probability of unstable stratification and stable stratifi- cation occurs much higher than the neutral and weakly unstable and weakly stable stratification. （2） Under stable stratifica- tion, the characteristics of the atmosphere change obviously in the vertical direction, which means that the hierarchical consid- eration is needed. According to the atmospheric turbulence observation experiment data, under stable stratification, the rela- tionship between the dimensionless velocity gradient and the stability ξ can be expressed as 1 ＋ βmξ, in which βm changes with the height： βm takes 4. 3 - 5.4 under 30 m height; βm takes 2.9 - 3.4 between 30 - 50 m; and βm takes 2.0 - 2.9 over 50 m.