复杂山地近地层强风特性分析

An analysis of the characteristics of strong winds in the surfacelayer over a complex terrain

中文关键词:  强风特性， 复杂山地， 近地层

英文关键词:Strong wind characteristics, Complex terrain, Surface layer

中文摘要:

      利用在贵州省西南部复杂山地上获取的近地层梯度风观测资料和三维超声测风仪观测资料， 从中筛选出具有该地气候特征的强风样本，利用数量统计和谱分析等方法，计算分析了由于复杂地形影响而导致的局地低层强风的平均和脉动特征。平均风场主要表现在受当地主要特征地形（西北—东南走向的深切峡谷）影响， 其全年的主导风向和最大风速出现的方向几乎完全转为沿峡谷走向，即使在符合中性大气层结条件下，风的垂直廓线也完全不满足幂指数分布，风攻角远远大于规范推荐的值，并且不同风向的强风攻角因地形影响其差异可达20°；强风条件下脉动风场的主要特征是：不同风向强风的湍流强度有所不同，在纵、横和垂直方向的湍流强度比值与现行设计规范给出的三维湍流强度比值有明显差异， 其中垂直方向的湍流强度显著偏大是突出特征； 湍流积分尺度偏大， 其中纵向值偏大20％—60％，横向值在某些风向上可偏大3倍以上，垂直方向则普遍较平坦地形偏大一个量级左右； 在桥梁结构较为敏感的频域范围内，各风向的湍流谱密度值有显著差异，其中不同风向在纵向上最大差值可达8倍，横向和垂直向可相差6倍， 但无论哪个方向的湍流谱密度值均比台风中心要小1—2个量级。

英文摘要:

      Based on the gradient wind data and three dimensional ultrasonic wind data observed in the surface layer over a complex terrain in southwestern Guizhou Province, strong wind samples with local climatic characteristics were selected. By using the statistical and spectral analyses, the mean and pulsation characteristics of strong winds in the local complex terrain surface layer were analyzed. Under the impact of the local terrain (a northwest southeast oriented deep gorge) the dominant wind direction and the direction of maximum wind speed are almost completely along the gorge. Even in the neutral atmospheric condition, the vertical wind profile is still totally inconsistent with the exponential distribution. The wind angle of attack is much larger than the recommended normal value, and due to the topographic effect, the difference between the attack angles of strong winds in different directions reaches up to 20°. Meanwhile, the main features of the pulsation wind field under strong wind conditions are: the turbulence intensity of strong winds in different directions are not the same; there is a significant difference between the ratio of turbulence intensity in the three dimensional directions and that given by the existing design specifications. Especially, the vertical turbulence intensity is significantly larger than the normal value, and the turbulence integral scale is much lager, i.e., 20％—60％ larger in the longitudinal direction, or even three times larger in the transversal direction, and one order of magnitude larger in the vertical than that over a flat terrain. Within the frequency domain to which the bridge structure is sensitive, the turbulence spectrum densities in respective directions are significantly different, among which the maximum difference for different wind directions can be as large as eight times in the longitudinal, and six time in the transversal and the vertical directions, respectively. However, the turbulence spectrum densities in all directions are 1-2 orders of magnitude smaller than those in a typhooncentre.