通过地面风速Weibull概率分布参数的阶段变化来描述城市化对地面风速的影响,并通过理论分析得出城市化进程导致其尺度参数c缩小,位置参数r增大的趋势效应的结论。将北京等8个城市1982—2005年地面天气资料定时数据按时间划分为前、后两个时段,分别拟合分布曲线的参数,对比前、后两个时段的拟合结果,验证了理论分析所得结论,即随城市的发展,各城市风参数c不同程度地缩小,r不同程度地增大,同时概率密度曲线的峰值均增大;不同城市的风速概率密度函数曲线变化特征有所不同,根据前、后时段概率密度曲线变化的特征,8个城市风速概率分布变化大致可分为A、B两种类型,两者的主要差异是A型变化特征为在曲线两端(大风和静风)的概率都减少,曲线分布更加集中;B型则是大风概率减少而静风的概率则增大,曲线向左移动;A型变化城市的r参数平均增大46.3%,明显大于B型城市的15.7%。初步资料分析还表明,风参数c和r变化幅度与城市化扩张速度有关。
In this paper, parameters of Weibull distribution were used to describe effects of urbanization on surface wind speed. Theoretical analysis indicated that urbanization could lead to a decrease in the scale parameter c and an increase in the location parameter r. Surface weather timing mode observations collected at Beijing and other 8 cities during 1982 - 2005 were divided into 2 segments based on different time periods and parameters of distribution curve were fitted respectively. Fitting results confirmed the conclusions that with the development of the city, parameter c decreased and parameter r increased in varying degrees, and their probability density peaks both increased. Characteristics of wind speed probability density function curves in different cities could be different. According to this feature, city wind speed probability distribution changes in the 8 cities could be divided into Type A and Type B approximately. The main difference in the features of the curves between the two types was that for Type A, both the strong and calm wind probabilities decreased as shown in both sides of the curve and the distribution become more concentrated; for Type B, the strong wind probability decreased but the calm wind probability increased and the curve moved to the left;r parameter increased by 46.3% in average in Type A cities, which was greater than that in Type B cities by 15.7%. Initial data analysis also indicated that the variation degree of wind speed parameter c and pa- rameter r was related to the speed of urban expansion.