Responses Of Summer High Temperature In Eastern China's Urban Agglomerations To Future Global Warming

Due to climate change and human activities,extreme weather events occur frequently and extreme high temperatures are very significant.Therefore,this paper makes use of the mesoscale meteorological model WRF(Weather Research and Forecasting Model)and the latest land cover data China LC,in the area of China.The three urban agglomerations in eastern China(Beijing-Tianjin-Hebei Urban Agglomerations,Yangtze River Delta Urban Agglomerations and Pearl River Delta Urban Agglomerations)are selected as the research object,and the dynamic downscaling of the RCP4.5(Representative Concentration Pathway4.5)scenario prediction results provided by the CESM(Community Earth System Model)climate model from CMIP5(Coupled Model Intercomparison Project Phase 5)is carried out.The regional climate changes at the time of increasing 1.5 ? and 2.0 ? in the future are simulated and studied.The results of downscaling prediction based on WRF/UCM show that when the temperature reaches 1.5°C and 2.0°C in the RCP4.5 scenario,the summer Tmean and Tmax of urban agglomeration in eastern China are significantly higher than those in the historical period.The increasing magnitudes of Tmax in 1.5°C and 2.0°C warming climate are 0.97°C and 1.17°C in BTH,0.88°C and 1.47°C in YRD,and 0.85°C and 1.22°C in PRD,respectively.The increase of Tmax in summer under different warming threshold is almost higher than that of Tmean in three urban agglomerations.In terms of extreme high-temperature events,in the future warming period of 1.5°C and2.0°C,the influence ranges of HWs in summer are significantly expanded,and the HWs indexes are significantly increased compared with the historical period.The growth rate of the three HWs indexes can reach more than 50% in the warming period of 1.5°C,and higher than70% in the warming period of 2.0°C,among which the growth rate of HWs intensity is more than 200%;From 1.5°C to 2.0°C,an additional 0.5°C temperature has the most significant impact on the future HWs of the YRD urban agglomeration,especially the HWs intensity will increase by 75.5%,far higher than other urban agglomerations.Compared with other major land cover types in each urban agglomeration,the warming response in urban areas is more prominent.In the warming period of 1.5°C and 2.0°C,the value of HWs indexes in urban area is far higher than that of other land cover types of each urban agglomeration.In the scenario of 1.5°C warming,the difference of HWs between urban and non-urban areas in PRD is particularly significant compared with other urban agglomerations,with the HWs frequency,duration and intensity in urban area of 74%,126%,and 200% higher than those of the fastest growing non-urban land cover type in PRD.