基于中国风能资源专业观测网的近地层风切变日变化特征

以中国风能资源专业观测网2009年5至10月10~120 m的梯度风观测数据分析了全国近地层风切变特征,结果表明:①风切变总体呈现规律性变化趋势,即:日出前和日落后切变指数较大,随着近地层温度升高,切变指数逐渐下降,近地层温度达到最高时,切变指数达到最低值,后随着日落、地面温度下降,切变指数逐渐上升,直到次日日出、日落周期;②因局地海(湖)陆分布的差异以及下垫面粗糙程度的不同,切变指数在各地的变化可归纳为如下几种类型:典型陆地型、海陆效应差异型、湖(河)陆效应差异型、特殊地形(峡谷)型、切变指数偏大型和特殊型;③从不同梯度间的风切变特征来看,低层(30 m附近)较为明显,而中高层(50 m和70 m)较小,说明30 m高度为我国近地层风速变化较为明显的层次。该研究资料序列短,可能在反映全国近地层风切变特征的普适性方面还存在一定的不足,但仍可作为我国风能资源丰富区近地层不同梯度间风切变分布和变化特征的重要参考,期望通过该研究的开展为风电场的布设及近地面层风能资源的利用提供技术依据。

Study of the Near Surface Wind Shear Daily Variation Characteristics Based on China’s Wind Power Resources Professional Observation Network

The near surface wind shear characteristics were analyzed in this article,using 10 m to 120 m gradient wind observation data from May to October in 2009,which came from China’s wind power resources professional observation network.The results show that: 1) The wind shear near surface presents regular variation trend: with large wind shear index before sunrise and after sunset,and it is gradually dropping with the near surface temperature increasing,and with the lowest shear index when the near surface temperature comes to a peak value,and then,with the sunset and the ground temperature drop,the shear index rising up again,until the next sunrise/sunset period.2) With different distributions of local sea or lake and land and with different roughness of the underlying surface,the wind shear indexes can be reduced to the following several types: the typical land type,the sea land effect difference type,lake or river land effect difference type,the special differences terrain(canyon) type,shear index partial large type and the special type.3) It is much more obvious at low level,near 30 m,than the relative high level,between 50 m to 70 m from the wind shear characteristics of the different gradient.So it is instability near the 30 m height in China.In this study,the analysis data sequence is short,and this may become the negative factor reflecting the universality law of the near surface wind shears characteristics in China,but it still becomes an important reference reflecting the near surface different gradient wind shear distributions and variation characteristics of the wind power resources rich area in China.It is expected that this study can provide some technical reference in building wind farm and in using near ground wind power resources in China.