全球增暖1.5/2℃下中国区域极端降水的风险变化及其影响因子

Risk and impact analysis of extreme precipitation over China under 1.5 and 2℃global warming levels

利用24个CMIP6全球气候模式的逐日降水模拟资料,基于广义极值分布(GEV)模型,研究了全球增暖1.5/2℃下我国20、50和100 a重现期极端降水的未来风险变化。可以发现,相对于历史时期(1995—2014年),全球升温1.5和2℃下极端降水发生概率风险空间分布相近,总体上呈现增加趋势,但额外增暖0.5℃将导致更高的风险。如50 a重现期极端降水,在增暖1.5/2℃下其重现期将分别变为17/14 a,极端降水将变得更加频繁。不同区域对气候变暖的响应存在区域差异,其中中国西部长江黄河中上游和青藏高原地区、中国东部长江黄河中下游及其以南地区,极端降水发生概率比达到3以上,局部更是达到5以上,为我国极端降水气候变化响应高敏感区域。进一步,基于概率分布函数从理论角度探讨了位置和尺度参数对发生概率风险的影响与贡献度量,并用于探讨极端降水气候平均态和变率变化对极端降水发生风险的影响,结果显示:位置和尺度参数的增量变化、风险变化率存在着显著的东西部差异,从而导致极端降水发生风险的影响因素存在差异。如中国西部尽管极端降水气候平均态和变率变化幅度不大,但因风险变化率较高,从而导致该区域的发生风险大幅增加;与之相反,中国东部风险变化率较小,但气候平均态和年际变率增幅较大,同样导致该区域风险增加依然较高;此外,相对于位置参数,全国大部分区域主要是尺度参数的变化导致极端降水未来风险增大。

Based on the daily precipitation of 24 global climate models from the sixth phase of the Coupled Model Intercomparison Project 6(CMIP6)multimodel simulations,the generalized extreme value distribution(GEV)is introduced to study the risks of extreme precipitation that expected to occur every 20,50,and 100 years over China under 1.5 and 2℃global warming levels.In comparison to the historical period(1995—2014),the changes in the probability of the risk of extreme precipitation under 1.5 and 2℃global warming present an overall increasing trend.Although their spatial distributions show similar characteristics,the additional half degree of global warming will lead to a higher risk.For example,extreme precipitation that occurs once every 50 years will become once every 14 or 17 years under the 1.5 and 2℃global warming,respectively,and extreme precipitation will become more frequent.There are regional differences in how each region reacts to global warming,among which the middle and upper reaches of the Yangtze and Yellow Rivers and the Qinghai-Tibet Plateau region in Western China,and the middle and lower reaches of the Yangtze and Yellow Rivers and their tributaries in Eastern China,are regions that are highly sensitive to climate change,with probability ratios of 3 or even 5 or more.Furthermore,the influence and contribution measures of location and scale parameters on the probability ratios are explored theoretically using probability distributions,which are also used to explore the influences of climate means and variability changes on the risks of extreme precipitation.The results show that there are significant differences between Eastern China and Western China in the incremental changes of location and scale parameters,and in the rates of probability changes,which lead to differences in the factors that influence the risk of extreme precipitation.In Western China,although the changes in climate means and variabilities of extreme precipitation are small,the probability ratios increase significantly due to the high rates of changes in probability.In contrast,the change rates are small,but the climate means and variabilities are increasing significantly,which also lead to an increase in Eastern China.Moreover,compared to the location parameters,the increased risks in most regions of China are mainly due to the anticipated changes in scale parameters of extreme precipitation.