STUDY OF RELATIONSHIP BETWEEN URBANIZATION SPEED AND CHANGE IN SPATIAL DISTRIBUTION OF RAINFALL OVER SHANGHAI

Using daily rainfall data of 11 observatory stations over Shanghai for the period 1960-2007,the spatial differences of rainfall over the Shanghai region during periods with slow and rapid urbanization respectively are investigated based on spatial standard deviation of rainfall and its relative variables.Results show that spatial differences increase with the acceleration of urbanization.Spatial distributions of annual rainfall and rainstorm frequency exhibit distinct urban ’rain-island’ features during the rapid period of urbanization(1960-1983) while it is opposite in the case of slow urbanization(1984-2007).Changes in the spatial distribution of annual rainfall trends also take place during different periods.Specifically,the variation of annual rainfall exhibits consistent trends over the Shanghai region in the slow urbanization periods.However,inconsistent spatial distribution of variations has taken place over the central districts and suburbs of Shanghai during the rapid urbanization stage.Since the speeding-up of urbanization,the annual rainfall amount over central districts of Shanghai tends to increase while that in the suburbs shows a decreasing trend.In addition,as far as different seasons are concerned,the speed of urbanization exerts insignificant influences on the spatial distribution of rainfall during winter and spring.On the contrary,the rainfall during summer and autumn(especially summer) is featured with an island effect during the rapid urbanization period.