宜昌地区中低空风速变化特征分析

利用宜昌1958—2013年逐日探空风资料,通过趋势系数、滑动t检验和小波分析等方法,分析宜昌中低空规定高度平均风速的时间变化,并和同期地面风速变化进行对比。结果表明：1）500和1 000 m高度月平均风速变化均呈双峰曲线,1 500和2 000 m月平均风速变化趋势较为一致,3 000 m月平均风速波动较大。2）从季节分布来看,500~2 000 m平均风速均为春季最大,3 000 m平均风速冬季最大;不同高度层季平均风速随高度上升增幅不同。3）500 m年和四季平均风速的年际变化最剧烈;500~2 000 m,年平均风速的离差系数随高度上升明显减小。4）1971—2013年,宜昌地面10、 500、 2 000、 3 000 m年平均风速显著减小;1 000和1 500 m年平均风速略有增大但未通过显著性检验。5）宜昌中低空平均风速主要经历了20世纪80年代由下降到上升和90年代由上升到下降的突变;冬季平均风速的突变次数最多,夏季平均风速突变次数最少;各高度年、季平均风速的突变次数随高度上升而减少。6）各高度普遍存在8~14 a的较长周期和2~4 a的较短周期,其中较长周期主要出现在夏、秋季,较短周期主要出现在春、冬季。

Analysis on Tendency of Middle and Low Air Wind Speed over Yichang Region

Based on the data of daily radiosonde wind (altitude below 3 000 m) from 1958 to 2013 in Yichang, the tendency variation of middle-low air wind speed over Yichang region are analyzed by using trend coefficient, moving t-test, and wavelet analysis, and the variations of middle and low air wind speed and surface wind speed in the same period are compared. The results show that: 1) Variation of monthly mean wind speed at 500 m and 1 000 m height are bimodal curves, the monthly mean wind speed at 1 500 m and 2 000 m height are more consistent, while the monthly mean wind speed at 3 000 m fluctuate violently. 2) Seen from the seasonal distribution, mean wind speeds at 500 m and 1 000 m height are maximum in spring, while the wind speed at 3 000 m height is the largest in winter; the vertical increased amplitude of wind speed vary at different altitude. 3) The annual and seasonal variations of wind speed at 500 m height are the fiercest; the deviation factor of annual mean wind speed decreases significantly from 500 m to 2 000 m height. 4) From 1971 to 2013, the annual mean wind speed on surface (10 m), and those of at 500 m, 2 000 m, and 3 000 m height all showed significant decreasing trend, while the annual mean wind speeds at 1 000 m and 1 500 m increased a little with no significance. 5) The middle and low air wind speed mainly experienced from decline to rise in the 1980s and from rise to decline in the 1990s; the number of abrupt changes is maximum in winter, and it is minimum in summer; in addition, the number of abrupt changes of annual and seasonal mean wind speed decreased with the increase of height. 6) There are long term cycle of 8-14 a and short term cycle of 2-4 a of annual mean wind speed at each altitude, that the former mainly concerned with summer and autumn, while the latter mainly concerned with spring and winter.