1958～2013年武汉市低空风速变化特征分析

ANALYSIS OF VARIATION OF WIND SPEED AT LOW-ALTITUDE IN WUHAN FROM 1958 TO 2013

采用武汉市1958~2013年逐日探空风资料,利用离差系数、气候倾向率、小波分析、Yamoto突变检验(信噪比指数)等方法,系统揭示该地低空(500、1 000、1 500、2 000 m)年、季、月平均风速的周期性与非周期性变化,通过指数曲线拟合揭示风速随高度变化特征。结果表明:(1)各层月平均风速均为双峰双谷型,7月、3~4月为峰,6月、9~10月为谷,7月达7.0~8.1m/s,谷值仅5.4~5.9m/s,即春夏季风速大,秋季小;(2)风速随高度上升呈线性或指数增加,地面至500m年、季平均风速增加约3.8~4.0m/s(地面仅约2.0m/s),a为0.241~0.294,从500m到2 000m年平均风速从5.9m/s升到6.9m/s,其中冬春季快,秋季慢,风廓线指数a为0.066~0.170;(3)各层年平均风速均呈减小趋势,1 500m、2 000m层达显著,每10a分别减小0.063m/s和0.074m/s,秋季减小显著,夏季减少不明显;(4)月平均风速离差系数为双峰双谷型(500 m为单峰型除外),主峰6~8月离差系数达0.15以上,1月为次峰,这些月风速年际变化大;(5)各层年平均风速周期均有12~30a(2 000m除外)、2~4a,500m层则为7~8a(仅1960’s),前者对应夏秋季,后者对应冬春季;(6)年、季平均风速均在1983~1986年突变上升和1991~1993年突变下降,且突变次数随高度减少,500m层最多,2 000m层除秋季外无突变。深刻认识这些特征可为本地区山区风电场规划、选址、设计、运营提供技术支撑。

Basing on the daily radiasonde wind speed data at Wuhan from 1958to2013,it is analyzed the cyclical and non-cyclical characteristics of average wind speed at low altitude(500、1 000 、1 500 、2 000m)within year,season and month,by the methods of coefficient of dispersion,climate tendency rate,wavelet analysis and SNR index,etc.Moreover,it is revealed the variation characteristic of wind speed with regard to altitude by the wind profile index a.The results indicated that:1)the monthly wind speed varied with the feature of double peaks and double valleys in each layer.The peak values appeared in July,March and April,and the valley values appeared in June,September and October.The wind speed was as high as 7.0-8.1m/s in July,and the valley value was only 5.4-5.9m/s.In another words,the wind speeds are high in spring and summer and low in autumn.2) Wind speed increased linearly or exponentially with altitude,the annual and seasonal average wind speed increased by 3.8-4.0m/s from surface to 500mheight(the wind speed of the surface is only about 2.0m/s),a was 0.241-0.294.The annual average wind speed increased from 5.9m/s to 6.9m/s as the altitude rising from 500 mto 2 000 m,where the wind speed was fast in winter and spring and slow in autumn.The wind profile index a was0.066-0.170.3)The annual average wind speed showed a decreasing trend,and the trend was significant in 1 500 m,2 000 mlayer.The annual average wind speed was reduced by 0.063m/s and 0.074m/s in each 10 a,respectively.The decreasing was significant in fall and unobvious in summer.4)The coefficient of dispersion of monthly average wind speed is in double peaks and double valleys type(except the 500 m height with single peak).the main peak of dispersion coefficient was more than 0.15 from June to August,and the subsidiary peak occurred in January.The annual variability of wind speed in those months was large.5)The cycle of annual average wind speed was 12-30 ain each layer(except 2 000mheight),2-4a,and was 7-8ain 500 mlayer(only in 1960').The former was concerned with the summer and autumn,while the latter was concerned with winter and spring.6)Annual and seasonal average wind speed both increased sharply from 1983 to 1986,and decreased sharply from 1991 to 1993.The number of abrupt change decreased with height,with maximum in 500 mlayer.There was no abrupt change in 2 000 mlayer except in autumn.These features in this study provide a technical support for wind power planning,site selection,design and operation.