辽宁省近地层风切变特征研究

Study on the Near Surface Wind Shear Characteristics in Liaoning Province

利用辽宁省风能资源专业观测网26座测风塔2009年6月至2010年5月10~70 m(100m)的逐时梯度风观测数据,研究了辽宁省近地层风切变特征,结果表明:近地层风速随高度变化基本遵循幂指数规律;各塔年风切变指数为0.024 4~0.405 0,没有明显的空间分布规律,主要受局地地形、地貌环境影响,个体差异较大;有11座测风塔年平均风切变指数大于B类风切变指数,26座测风塔空间平均年风切变指数为0.155 1,也略大于B类风切变指数;风切变指数呈现明显的白天小、夜间大的日变化特征,与气温的日变化呈反位相;春季风切变指数明显偏小;大气中性条件下的风切变指数与年平均风切变指数基本相当,稳定状态下风切变指数明显偏大,不稳定状态下最小;风切变指数具有随风速增大而减小的特点,大风条件下的平均风切变指数小于年平均风切变指数,多数测风塔风速≥15 m/s时风切变指数下降至0.1以下。

The near surface wind shear characteristics were analyzed using 10 m to 70 m(100m) hourly gradient wind observation data of 26 wind towers from June 2009 to May 2010. The results are as follows. The variation of wind speed with height accords with exponential function. The yearly wind shear indices at different wind tower vary remarkably from 0.0244 to0.4050, with no obvious spatial characteristics, which is affected by local terrain and physiognomy. The wind shear indexes at 11 wind towers are more than 0.15(standard B,came from GB50009-2012) and 0.143(reference value came from GB/T 18710-2002). The spatial average yearly wind shear index of 26 wind towers is 0.1551, which is also a little more than standard B and 0.143(reference value came from GB/T 18710-2002). So it needs to pay attention when quoting the reference values directly in the wind engineering if there is no local observation.The obvious daily variations of wind shear index show that large wind shear index occurs before sunrise and after sunset, and it gradually drops with the increase of near surface temperature. The wind shear index is the lowest in spring comparing with other seasons. The wind shear index under neutral atmospheric condition approaches to the yearly average wind shear index, and it is higher under stable condition and lower under unstable condition. The average wind shear index decreases with the increase of wind speed, which is lower than the yearly average wind shear index under strong wind condition. For a great number of wind towers, the wind shear index is less than 0.1 when wind speed is more than ≥15 m/s.