复杂地形上的低层风场特征

为了获得复杂地形上的城市地区低层风场特征,结合各个分散站点的实测风场资料,利用质量守恒风场调整模式M CF进行了三维风场模拟分析。以北京为例,对该地区低层大气的平均流动状况和局地扰动状况进行了模拟,获得了该地区流场总体平均状态和局地扰动状态的时空变化。结果表明:该地区风场季节变化主要受大尺度背景风场决定;流场的垂直分布主要由地形和背景风场共同决定。冬季流场主要受地形动力作用,而夏季则受热力作用,具有很强的局地环流;晴稳天气条件下,低层流场受地形扰动影响较强,其影响表现为水平涡旋形态,城市对涡旋产生也具有显著的影响。

Characteristics of wind field in low layer over complex terrain

In order to acquire the surface wind fields of the urban area over the complex terrain,three-dimensional wind fields were analyzed with mass consistent model for wind fields(MCF) based on the historical data from isolated observation stations.A sample of the Beijing area was presented.The characteristics of the mean wind and perturbation over the area were studied.Results show that the mean wind of seasonal variation depends on wind fields of large scale system.The vertical wind profile was determined by the local terrain and the background wind field.It was influenced by the dynamic and thermodynamic interaction of surface.In winter,it was mainly controlled by the background wind field,but in summer by the local topographic effect.In the fine and stable weather,the topographic perturbation displays as a horizontal swirl and it is also obviously influenced by the urban location.