Impact Of Urbanization In Different Regions Of Eastern China On Precipitation And Its Simulation

Climate effect caused by urbanization has been an indispensable artificial factor in regional climate change research. Based on daily precipitation data, the possible effects on precipitation of the development of three urban groups in east China are discussed, with three division methods between cities and rural according to the total number of population, persons density, and MODIS land cover data separately. The effects of urbanization on extreme precipitation in summer and winter are also detected by using high resolution merged precipitation product. CAM5climate model is used here to explore the possible links between urbanization and summer precipitation in Huabei. The main findings are as follows.1) Three methods are used to classify city and rural according to the total number of population, persons density, and MODIS land cover data. The uniformity identification results show that in1960-2009and1980-2009, the urbanization in Yangtze River Delta and Pearl River Delta city groups may bring more precipitation in these areas, while less in Jing-Jin-Tang city group.2) The difference of precipitation between city and suburb in1960-1979is slight. While it is more evident in1980-2009that urbanization has positive effects on precipitation in every city group. The difference of precipitation between city and rural is sensitive to the ways to divide countryside from city which may cause uncertainties in1960-1979, while in1980-2009, it is very different. The single that urbanization favours more precipitation is more obvious and stable.3) Precipitation features in different seasons show that the changes of precipitation between city and rural are relatively unanimous among different division methods in1960-2009. 4) Precipitation in Yangtze River Delta reduces in spring and autumn, and increases in summer and winter. However, it is exactly opposite in Jing-Jin-Tang. Spring precipitation in Pearl River Delta increases in city and decrease in rural. The precipitation both in city and rural increases in summer and winter, and decreases in autumn. The single that city favours more precipitation is obvious in every season in Yangtze River Delta and Pearl River Delta in1980-2009. It is robust to the different ways to divide countryside and city. However, effects of different division methods on seaseanal precipitation are relatively small. The effects of urbanization are not obvious in1960-1979. The changes of precipitation in different seasons between city and rural in the three city groups are sensitive to the division methods.4) Extreme precipitation results show that good relationship exists between the extreme value center of precipitation intensity in summer in Yangtze River Delta and Pearl River Delta city groups and city, especially the extreme precipitation intensity. There is more extreme precipitation in city than that in rural in summer. The ratio of extreme precipitation shows an increase tendency with the increasing of population, especially in su-xi-chang and ning-zhen-yang. These results indicate that urbanization may have positive contribution to extreme precipitation in summer. However, the effects of urbanization in winter are insignificant.5) Modeling results show that urbanization in east China can excite an anomalous anticyclone in northern China. The subsidence associated with the high pressure anomalies in mid-and high troposphere tends to suppress the local cloud formation and convectional activity, which reduce precipitation in Huabei. As a result, the urbanization in east China may enhance the tendency of "Northern-drouhgt".