城市化进程对重庆都市圈降水空间分布的影响

Influence of Urbanization Process on the Spatial Distribution of Rainfall over Chongqing Metropolitan Region

利用重庆17站逐日气象观测资料、重庆统计数据,采用降水量空间标准化方法,研究了城市化进程不同阶段对重庆都市圈降水空间分布的影响。结果表明:重庆城市化进程能够以1997年为界限被划分为城市化缓慢发展阶段和快速发展阶段,都市圈年降水量变化的空间差异与城市化进程的速度有关。比较两个阶段的差值,发现随着城市化进程的加快,核心都市圈年降水量、降水强度、中雨和暴雨日数都有所增加,呈明显的"城市雨岛"特征。从季节差异来看,夏季降水以主城区及其北侧郊区降水增加,冬季降水以主城区及其南侧郊区增加为主,可能是因为城乡温度梯度与环境风场相互作用,导致不同季节降水分布的区域差异,使得主城区及其下风方向降水增加,且以下风区增加最为显著。

Daily meteorological observation data of 17 stations and yearly statistical data of Chongqing were employed to diagnose the influence of urbanization on the spatial distribution of rainfall over Chongqing metropolitan region by adopting the method of spatial standardization of precipitation. The results showed that the period of 1970--2009 was divided into two stages by the year 1997, that is the slow developing stage of urbanization and the quick developing stage of urbanization, and spatial difference of annual rain- fall over the metropolitan region has relations with the acceleration of urbanization. Comparing the differ ence of the two stages, it is found that with the fast development of urbanization, the annual rainfall a- mount, rainfall intensity and the frequency of moderate and torrential rains has got increased, showing the distinct feature of urban ＂rain-island＂. In addition, as far as seasonal difference is concerned, urbanization has exerted different influence on spatial distribution of precipitation over the metropolitan region in Chongqing in summer and winter. The urban areas and the suburb in the north of the city see more rains over summer time while the increase of precipitation happens in the urban areas and its suburb in the south in winter. Such spatial distribution of rainfall in different seasons is possibly caused by the interaction be- tween seasonal prevailing wind and the temperature gradient of urban areas and suburbs so that the rainfall in the urban and its downwind areas has increased significantly, especially in the downwind areas.