The Impact And Future Risk Changes Of Regional Climate Extremes In China

Summer extreme precipitation events on a regional scale in China have increased significantly under global warming,and summer extreme precipitation also has significant interdecadal changes.In addition,extreme climate events that occur simultaneously or consecutively have a more serious impact on the environment and human society than individual extreme weather events.In this study,Global Mean Temperature(GMT),decadal(Pacific Decadal Oscillation,PDO)and multi-decadal variation(Atlantic Multidecadal Oscillation,AMO)indices are taken as covariates into the Generalized Extreme Value model(GEV)parameters to investigate the response characteristics of summer extreme precipitation to external forcing(GMT)and internal variability(PDO,AMO).At the same time,the Copula model is used to describe the joint distribution characteristics of summer precipitation and temperature,and to analyze the future risk of compound events.The results show that:(1)Based on the non-stationary GEV model,the regional characteristics of the response of extreme summer precipitation to external forcing were investigated.The results show that GMT has a statistically significant impact on the summer extreme precipitation of about 17.5% stations in China.When the GMT increases by 1?,the RL20(20-year return level of maximum daily precipitation)of stations in northern North China and southern Northeast China decrease by 10-30%,and the return period extended to 25-45 years;the RL20 of stations in the middle reaches of the Yellow River and the middle and lower reaches of the Yangtze River and its south increase by 10-30%,and the return period shortened to 5-15 years.Meanwhile,the variation of GMT may contribute to the trend of summer extreme precipitation.(2)Based on the non-stationary GEV model,the regional differences in the response of summer extreme precipitation to internal variability were analyzed.The results show that PDO and AMO have statistically significant impact on the summer extreme precipitation of about 26.8% stations in China.Among them,about 9.98% and14.3% of stations are significantly impacted by PDO and AMO,respectively.When PDO changes from negative phase to positive phase,RL20 of North China station decreases by 10-30%,and the return period extends;RL20 of the middle and upper reaches of the Yangtze River and its south region increases by 10-30%,and the return period is shortened.The extreme precipitation sequence in North China is negatively correlated with PDO index,while the middle and upper reaches of Yangtze River and its south are positively correlated with PDO index.When AMO changes from negative phase to positive phase,RL20 of the stations in the south-east,the middle and lower reaches of the Yellow River and its south,the middle and lower reaches of the Yangtze River and its south region increases by 20-50%,and the return period is shortened;RL20 of some stations in North China is reduced by 20-40%,and the return period is extended.The extreme precipitation in northern North China is negatively correlated with AMO index,and that of the lower reaches of Yangtze River and south of Yangtze River is positively correlated with AMO index.(3)The relationship between summer precipitation and temperature was investigated,and the Copula model was used to describe the joint distribution characteristics of the two,and the future risk of compound(warm/dry,warm/wet)events was estimated.The results show that the summer temperature and precipitation are negative correlated in most areas over China.Under the 1.5?(2?)warming,the regional average risk of warm event,wet event and dry event increases by 2.30(2.83),1.16(1.29)and 0.86(0.82)times respectively,and the risk of warm event and wet event increases by 1.5?4 and 1?2 times in most areas.With global warming,the risk of warm and wet events in China increases significantly,while the risk of dry events decreases.When global warming is 1.5?,the regional average risk of warm/dry and warm/wet events increases by 1.82 and 5.48 times.In most areas,the risk of warm/dry and warm/wet events increased by 1-3 and 3-9 times.When the global warming is 2?,the regional average risk of warm/dry and warm/wet events increases by 2.04 and 10.01 times.The risk of warm/wet events in the western Northeast China,North China,Northwest China and South China increased more than 9 times.