AN ANALYSIS ON THE DISTRIBUTION OF PRECIPITATIONAND RELATIVE HUMIDITY IN THE URBANREGION OF BEIJING
北京城区的降水与湿度分析

It is explained in this article that there exist evident dry island in summer and wet island in spring and winter in urban region, and in autumn both dry and wet islands can appear. Th-rough the comparsion of the precipitation and relative humidity data from the observation points in the urban and suburban regions of Beijing in recent years. The formation of the dry of wet island is not entirely due to the precipitation. On the contrary, in summer, the precipitation in urban region is larger than that in suburbs, but owing to the main pattern of rainfall is storm and flow away quickly on the solid underlying surface, the moisture in urban region during summer becomes lower than that in suburbs. In winter and spring the underlying surface in su-burbs of Beijing is very dry and cold, which decreases the evaporation, so the moisture is lower than that in urban region where the evaporation so the moisture is lower than that in urban re-gion where the evaporation is much more stronger because of large water surface of lakes and more waste water, and also warmer condition of heat island there. The solid precipitation also effect the formation of wet island in urban region. The clear seasonal occurrence of urban wet and dry island reminds that the differences in the characteristics and conditions, as well as their seasonal variation of the underlying surface may be the main factors of the wet and dry island formation. This article also ahalyzes the influence of the city to the precipitation and the contribution of precipitation in urban region to the water resources management and regulation. It is pro-posed that the proportionally and homogeneously develop the water bodies and vegetation area as the urban region grows, is very necessary to create a comfortable environment for the inha-bitants.