Preliminary Study On The Influence Of Urbanization On Precipitation Changes In North China

North China is the area studied in this paper. According to their location, population and satellite image, state base and reference weather stations there are classified into 5 types: country stations, small city stations, medium city stations, big city stations and reference stations. Most attention is paid to how the urbanization can affect precipitation. The variability of North China precipitation is also studied.45 years of monthly precipitation data from North China weather stations are used in our study, which span from 1961 through to 2005. Quality control and homogeneity test are performed to the original data before the analysis. Two kinds of periods are selected in our study, one is from 1961 to 2005, namely the whole period of time that data covers, the other is from 1980 to 2005, during which the urbanization is rather rapid. Regional mean is mostly concerned in this study, but furthermore 3 cities are selected to perform case study. The main results are:During the past 45 years, there is an obvious decrease trend in North China precipitation. Different from the 45-year result, precipitation shows a slight increase, instead of decrease trend in the recent 26 years. All kinds of stations show the same trend as the one of North China as a whole, but different in the extent and variability.Trend study of all kinds of stations shows that urbanization leads to more precipitation on both the yearly and seasonal time scales. This will strengthen an abnormal increase of precipitation and therefore weaken the natural decrease trend in North China to some extent. The more urbanized a station is the more impact will be found of urbanization on the precipitation. This effect is more obvious in summer than in other seasons and more obvious in the last 26 years than in the whole 45 years. Similar results can be found in the reference station, but the extent is among all kinds of city stations.