| Mean temperature of China has shifted towards warmer direction,while large regional differences lie in the changes of mean precipitation,but there is an overall enhancement in the precipitation extremes.More attention should be paid to the development and evolution of the extreme climate events,for they may lead to direct disastrous impacts on the natural,social and economic systems.It is an effective approach to understanding the impacts of climate change by simulations and projections of the mean and extreme climatic status using climate models.The regional climate modeling system PRECIS(Providing Regional Climate for Impacts Studies)is a dynamic downscaling method developed by the Hadley Center,which is to allow developing countries or groups to generate regional scenarios of climate change for use in impacts studies.In this paper,the data used were daily temperature,precipitation,maximum temperature and minimum temperature in 1961-2099 within mainland China under RCP(Representative Concentration Pathway)scenarios,namely RCP2.6,RCP4.5 and RCP8.5scenario that were generated by PRECIS through one-way nesting to HadGEM2-ES,which is a Global Climate Model that participates in the fifth phase of the Coupled Model Intercomparison Project(CMIP5).In which the period 1961~1990 was defined as the climate baseline period,which is used to test the simulation ability of PRECIS and to calculate the relative changes of future climate events,and the project period in the 21st century were divided into 3 periods,which were early stage(2011~2040,2020s),medium stage(2041-2070,2050s)and late stage(2071~2099,2080s),respectively.The simulation ability of PRECIS was tested at first,and then the changes of mean climatic status and climate extremes are projected with the application of reasonable extreme climate indices.Main results are listed below:(1)PRECIS has a considerable simulation capability in the annual mean temperature and precipitation,and the simulation of temperature is better than that of precipitation,there is still big bias in precipitation simulation,however,the spatial simulation ability has been greatly improved than the previous version.The annual mean temperature of China is projected to increase by 2.4~6.4~oC by the end of the 21st century,and the warming magnitude is larger in northern than southern part of China.There is relatively big variation in changes of precipitation,it is projected to change by-1.3%?9.0%and6.5%,respectively,under RCP2.6?RCP4.5 and RCP8.5 scenario.Precipitation should increase in northern part of China and the Tibetan Plateau,while it should decrease in the eastern part of Southwest China and the lower reaches of the Yangtze River.(2)Both of the maximum and minimum temperature of China would shift towards warmer direction under climate warming,but there are some regional differences among the“asymmetry warming”.The minimum temperature would warm more than the maximum temperature in Northwest,Northeast,North China and the Tibetan Plateau,while the maximum temperature warms more than the minimum temperature in Central,South,East and Southwest China.The frequency and intensity of the extremes related with high temperature would become more,while those related with low temperature would become less current.Hot days would increase more in the southern and southeastern part of China;frost days would decrease obviously in the Tibetan Plateau and western part of Southwest China;high temperature days would increase more in the eastern and southern part of Tibetan Plateau and South China,and low temperature days would decrease all over China,especially in the Northeast China.The thresholds for temperature extremes would increase by large magnitude by the end of the21st century.It can be inferred that a reduction in greenhouse gas emission can be contributable for controlling the evolution trends of extreme temperature events.(3)Extreme precipitation events in China would be enhanced,and heavy rain should increase no matter the regional precipitation would increase or decrease in the future.Consecutive dry days would decrease,which can be mainly attributed to the reduction in northern China and the Tibetan Plateau,while they would increase in the southern and southeastern coastal areas.All of the simply daily precipitation intensity index,maximum 5-day precipitation and annual total extreme precipitation amount indices would increase in the future.Southern part of China may become the“hot spot”in precipitation extremes analysis in the future,for both of the flood frequency and drought duration would increase in the future;while in the northern part of China,flood frequency is projected to increase,but the drought duration would be shortened in the future.It would be benefit for reducing the extreme precipitation risks by controlling GHG emissions.(4)This paper argues that the drought area based on SPEI index is more consistent with the actual agricultural drought occurrence when compared with the SPI index.When comparing the aridity trends,the degree of drought would increase based on SPEI,while it would decrease based on SPI,which can reflect the impacts of warming on the drought tendency.The aridity trend is more severe under RCP8.5emission scenario,and its climate tendency rate is as much as 1.5 times of that under RCP4.5 scenario and it is about 1.8 times of that under RCP2.6 scenario.In the future,different drought occurrence areas would increase by different magnitudes,while no drought areas would decrease consistently,which would decrease by 43%?51%and 76%,respectively,under RCP2.6,RCP4.5 and RCP8.5 scenario.The EOF analysis for SPEI index showed that all of the main modes under three RCP scenarios were favorable of the drying tendency in almost all regions over China,and the typical areas located in Northwest China,eastern part of Southwest China and Central China.The time coefficient of the first mode would increase with time,meaning that this spatial pattern would become more and more typical.The sensitivity of drying tendency to climate change varies from regions,and the more responsive regions to climate change are located in Northwest and Central China.This paper gave out a systematically projection of the spatial and temporal changes of climate extremes over China,which can provide the scientific database for national GHGs emission reduction measures and adaptation to climate change. |
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