Impact Of Urbanization On Surface Warming In Eastern China

With the homogeneity-adjusted surface air temperature (SAT) data at549stations and the meteorological data at760stations in China for1979-2008, a preliminary detection of climate change is conducted with linear trend method. Meanwhile, on the basis of the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, the temporal evolution and spatial pattern of urbanization in eastern China is presented. Finally, the spatial heterogeneities of the SAT trends on different scales are detected with the spatial filtering (i.e. moving spatial anomaly) method, and the impact of urbanization in eastern China on surface warming is analyzed. The main conclusions are as follows:(1) Warming signals can be observed significantly in each season for1979-2008in China. The warming is more remarkable in spring and autumn than winter and summer. Meanwhile, the spatial pattern of the warming is more heterogeneous in summer and winter.(2) The bright nighttime light mainly located in the northern and eastern China, especially confined in the Beijing-Tianjin-Hebei (BTH) city cluster region, Yangtze River Delta (YRD) city cluster region and Pearl River Delta (PRD) city cluster region. The descending order of their scale is YRD, PRD and BTH. Besides, the rapid urbanization in the BTH and YRD regions mainly occurred after2000and the city cluster pattern has been formed in these regions by2008. However, the rapid urbanization in the PRD region began to develop in1992and has formed the city cluster pattern by2000.(3) The SAT is characterized by a significant large-scale increasing trend from1979to2008in eastern China. The annual mean warming rate is estimated to be0.5℃per decade. The difference between urban and non-urban stations indicates that the warming rate of urbanization effect on annual mean temperature is0.057℃per decade, accounting for11.4%of total averaged warming in whole eastern China. Overall, the urbanization effect has obvious seasonal variation, which appears to be more significant in winter and spring, and relatively weak in autumn and summer.(4) A spatial filtering (i.e. the MSA) method is proposed to detect the spatial heterogeneity of the SAT trends. The MSA distribution exhibits a significant summer urban warming in the YRD region and a significant winter urban warming in the BTH region. The YRD warming in summer primarily results from the increasing of maximum temperature while the BTH warming in winter is due to the increasing of minimum temperature.(5) The urbanization in the BTH region has significant impact on the increasing of winter minimum temperature with an estimated urban warming rate at0.102-0.214℃per decade, accounting for12%-24%of the total regional warming. The urbanization in the YRD region primarily affects the summer maximum temperature with an urban warming rate at0.132-0.250℃per decade, accounting for36%-68%of the total regional warming. Winter maximum temperature in the PRD region is also increased by urbanization at a rate of0.076-0.125℃per decade, accounting for20%-32%of the total regional warming.