乌鲁木齐市近地层风切变指数特征

Characteristics of the Wind Shear Exponent of the Near-Surface Layer in Urumqi City

利用乌鲁木齐市 5 座100m 气象铁塔2012 年6 月-2014年 4 月10 层风速观测资料, 应用统计学方法详细分析了乌鲁木齐市城区和郊区近地层风切变指数特征, 得出以下结果： 乌鲁木齐市风切变指数分布范围在-1.5~1.5, 基本呈正态分布.风切变指数与风速大小关系密切, 当风速〈1 m/s时, 切变指数变化较大; 当风速〉2 m/s时, 切变指数变化较小.城区和郊区最大切变指数出现高度差异较大,南郊燕南立交切变指数最大在36~46m,城区水塔山在60~77m, 城区鲤鱼山在13~22m, 近北郊红光山在46~60m, 北郊米东在 28~36m.各层切变指数白天变化幅度大, 夜间变化幅度小. 切变指数日变化不规律与城市边界层变化的复杂性密切相关. 降温幅度大的秋季-冬季时段, 易出现切变指数小于0 的情况.

The characteristics of the wind shear exponent of near -surface layer in urban andsuburban areas were statistically analyzed based on the wind speed data obtained from five 100mmeteorological towers in Urumqi between June 2012 and April 2014. The result showed that thewind speed power exponent was normal distribution and its value was in the range of -1.5~1.5.Also, the result showed that the wind shear exponent was closely related to the wind speed. Thewind shear exponent was significantly changed when the wind speed was 〈1 m/s, while the windshear exponent was slightly changed when the wind speed was〉2 m/s. There was a significantlydifferent height and their biggest values appeared in 36~46 m, 60~77 m, 13~22 m, 46~60 m and28 ~36 m at Yannanlijiao, Liyushan, Shuitashan, Hongguangshan and Midong, respectively. Thevariation of wind shear exponent in each layer was strong during the day, while it was weak at night.The diurnal variation of shear index was closely related to the complexity of the change of urbanboundary layer. In both fall and winter, it was a frequent appearance that the wind shear exponentwas〈0.