中文摘要：

我国风能丰富的地区主要分布在沿海和＂三北＂地区,本文基于这些地区13个风电场全年共668572个测风样本得出了平原、山地和沿海三种地形不同地表状况下近地层风随高度变化特征。结果表明：虽然近地层风廓线形态多变,但风速随高度单调增加占绝大多数,可以用幂函数较好的拟合逐时风廓线;幂函数的指数即切变系数不仅受地表粗糙度影响,还受地形、风速大小以及热力层结影响,切变系数山区小,平原大,沿海比平原稍小;在我国北方地区,年平均切变系数有如下统计规律：山区草地为0.1以下,草原为0.15,同类地形随地表粗糙度增大而明显增大,大风段山区灌木比草地大30%。该结果可用于北方相似下垫面下的风能评估和风电场预可研调查。

英文摘要：

China’s wind-rich areas are primarily distributed in coastal areas and the Three North region. In order to reasonably assess wind resources and effectively exploit wind energy over these regions, 668,572 surface layer wind profiles from thirteen tall wind towers were collected. The wind towers are 70 m high and there are 4~5 layers for measurement wind velocity. Underlying surface characteristics of these wind towers are different. In general, there are three types of terrain, i.e., coastal areas, mountainous areas, and plains. Vegetation varies greatly with terrain, resulting in varying roughness. This study investigated characteristics of surface layer wind profiles over different underlying surfaces. Results show that the structure of the surface layer wind speed profiles is different. There are seven types of wind speed profiles. The wind speed decreases with height at some levels, but the wind speed increasing with height is predominate, with 70% of profiles pertaining to the increasing type. Each wind profile can be fitted using the simplified power exponential function. The exponent is named shear exponent. The annual average shear exponent （α-） and the shear exponent of annual average profile （ αv-） were derived,that means there＇s two shear exponents at one wind tower. The former is used in wind power projects and the latter is used in meteorology. [α] is similar for the same type of underlying surfaces, but [αv] varies with the underlying surface. For example, the shear exponent of the annual average profile will vary from 0.15 to 0.23 at five wind towers in Inner Mongolia, located at the same latitude, and the underlying surface is grassland. Only for the strong wind （ 8m/s） segment, there is no obvious difference between two shear exponents. In general, the shear exponents vary with surface roughness, topography, and wind speed magnitude as well as its instability. The shear exponent of plains is generally larger than mountainous areas. The shear exponent of coastal areas is slightl