The Impact Of Urbanization On Extreme Temperature In The Middle And Lower Reaches Of Yangtze River

Based on the daily temperature dataset of Chinese763stations,the NCEP/NCAR reanalysis database,DMSP/OLS nighttime light imagery data and the74circulation indexs,using the surfer,Gis and OMR method,the impact of urbanization on extreme temperature in the Middle and Lower Reaches of Yangtze River and its spatial and temporal distribution characteristic are analyzed.The main results are:(1) The annual and seasonal high temperature days experience a first drop then rise process, overall show a rising trend and the summer high temperature days show the weakest trend. The years of mutation show the earliest in the spring but the latest in the summer. Annual, spring, summer, autumn and winter high temperature days all show4,4,4,4,3obvious features of time cycle scale. The annual high temperature days show a rising trend in the middle area but shows a decreasing trend in the north and south area.Meanwhile,the high and low centers of the annual and seasonal high temperature days are different.(2) The annual and seasonal cold days experience a first rise then drop process, overall show a decreasing trend and the autumn cold days show the weakest trend. The years of mutation show the earliest in the winter but the latest in the summer. Annual, spring, summer, autumn and winter cold days all show4,4,4,4,3obvious features of time cycle scale. The decline high value centers of annual, spring, summer, autumn, winter cold days are respectively located in the Yangtze river delta region and the southeast area of hubei, the north of jiangsu and anhui province, the north of hubei province, the eastern part of hubei province,the southeast coastal area of Zhejiang province. The high and low centers of the annual and seasonal cold days are different.(3)The OMR average,minium temperature show a rising trend while the maximum and diurnal range temperature show a decreasing trend.The impact of urbanization on average and minium temperature are most significant in spring,but are most significant in autumn for maximum and diurnal range temperature.(4) Whether annual or seasonal, the impact of urbanization on average, minimum temperature in metropolis is the largest, while the impact on maximum,diurnal temperature range in large citys is the largest. The contribution of urbanization on temperature are the same.(5)The OMR seasonal high temperature days show a decreasing trend,with the summer high temperature days show the strongest trend,and the big citys show the most significant response to the urbanization;The OMR seasonal cold days also show a decreasing trend,with the winter cold days show the strongest trend,and the metropolis show the most significant response to the urbanization.(6) In high(low) temperature induced circulation background,the impact of urbanization on high temperature(cold) days is negative,and the effection of urbanization strengthen with the circulation strengthen.