中文摘要：

利用线性拟合、小波分析、Mann-Kendall方法对华北平原104个测站空间平均的近56年来的逐日风速资料进行了倾向、周期、突变等特性分析。研究结果表明：1951年～2006年间,华北平原风速呈减小趋势,变化率约为-0.016m（/s·a）,四个季节中冬季风速降低趋势最为明显,递减率也最大-0.022m/（s·a）,而夏季风速递减趋势最不明显。风速的长期变化还具有一定的突变性,年平均风速在1980年前后出现明显的突变点,从各季节平均风速来看,夏、秋季突变出现的时间稍早于春、冬季节,且夏季突变情况较复杂,出现多个突变区域。到90年代时,各季平均风速的M-K统计量UF的平均值都超过或接近0.05显著水平的临界值,表明风速开始显著下降。复值Morlet小波分析的结果显示,风速变化存在1a、8～10a以及15～20a左右的变化周期。

英文摘要：

The spatial-temporal dynamics of wind velocity are essential to climate change research and terrestrial water cycle, as it is a crucial driving force for evapotranspiration （ET）, and is also closely related to the fully realization of clean energy target. In order to investigate the variation characteristics of wind velocity on the North China Plain, the daily wind velocity data from 104 stations in the North China Plain over the past 56 years were collected and analyzed by using the methods of linear regression （taken time as an independent variable）, wavelet analysis and Mann - Kendall test. The results showed that a significant declining trend of wind velocity existed in the study region during the period of 1951-2006, at the rate of approximately -0.016 m/（s·a） （R^2=0.66738, P〈0.05, n=56）. This was in accordance with the research result of the declining rates in middle latitude countries, within range of -0.004 m/（s·a） to -0.017 m/（s·a）. Furthermore, the declining process mainly took place in the middle and late 1990s. Linear regression results demonstrated that wind velocities in the four seasons were all statistically significant at the level of 0.05, with F values of 67.3311, 46.4803, 55.3640 and 121.4878 from spring to winter. In the four seasons, wind velocity in winter （December, January and February） exhibited the most significant declining trend with the highest declining rate of -0.022 m/（s·a） （R^2=0.69229, P〈0.01, n=56）. , the declining trend of annual average wind speed in summer is less significant. Abrupt change was found in the long-term climate variation. The results showed that on an annual wind speed basis, the year of 1980 can be viewed as turning point of the abrupt change;while from the perspective of seasonal wind velocity, the abrupt change points in summer and autumn appeared slightly earlier than those in spring and winter. The situation in summer was comparatively complicated by multiple changing points. Complex Morlet wavelet analysis revea