全球变暖背景下区域水热条件发生明显改变,导致极端水文气象事件频发,特别是复合型极端事件日益增多,严重威胁了生态环境、公共安全与社会经济发展.长江流域一直以来都是中国极端灾害最频繁的地区之一,受全球变暖影响,近年来也经历了更严重的干旱—热浪复合事件(compound drought and heatwave events,CDHEs),严重制约了长江流域生态保护和高质量发展.为此,论文以长江流域为例,基于长期历史观测资料和CMIP6模式预估数据,采用强度指数(compound drought and heatwave magnitude index,CDHMI)识别长江流域CDHEs,并探讨CDHEs时空演变规律及未来趋势.结果表明:①历史时期,CDHEs频次和持续时间在1993年后均呈增加趋势.轻度等级的CDHEs发生频次最高,7月的频次和持续时间均为最高,主要发生在长江流域中下游、横断山区和云贵高原等地区.② 23种CMIP6 模式中 INM-CM4-8、ACCESS-ESM1-5、NESM3、NorESM2-LM 和 INM-CM5-0 是偏差校正后最适合长江流域的5种模式.③未来长江流域中下游地区是CDHEs频次和持续时间的高值区,5种模式中NorESM2-LM的年均频次和持续时间最高;多模式集合结果表明,不同情景在近期的差异较小,远期差异明显;SSP1-2.6、SSP2-4.5和SSP5-8.5三种情景下轻度等级CDHEs的年均频次均为最高,轻度、中度、重度和极端4种等级事件在SSP5-8.5达到峰值.研究结果可为长江流域缓解未来的气候变化风险提供科学支持.
Historical changes and future prediction of compound drought and heatwave events in the Yangtze River Basin
Global warming has led to accelerated changes in the global hydrological cycle,resulting in an increasing number of extreme events and compound events in which multiple extreme events occur simultaneously or consecutively,and are more hazardous than a single extreme event.The Yangtze River Basin has always been one of the areas with the most frequent extreme weather and climate events and disasters in China and has also experienced more severe compound events in recent years due to global changes,which has seriously constrained ecological protection and high-quality development in the region.The Yangtze River Basin is one of the most populous and economically developed regions in China,and climate change and human activities have significantly affected the distribution of water and heat conditions in the region.Therefore,taking the Yangtze River Basin as an example and based on long-term historical observations and CMIP6 model prediction data,this study adopted the compound drought and heatwave magnitude index(CDHMI)to identify compound drought and heatwave events(CDHEs)in the Yangtze River Basin,used cumulative probability density curves to classify the intensity of CDHEs,and explored the spatial and temporal evolution patterns of the compound drought and heatwave events as well as the future trends.Meanwhile,to ensure the accuracy of the data,the applicability of the 23 CMIP6 models in the Yangtze River Basin was assessed using three evaluation metrics,which improved the credibility of future CDHEs predictions.Finally,the spatial changes of CDHEs in the Yangtze River Basin under different future scenarios were characterized based on a multi-model ensemble of 23 CMIP6 data.The results of the study show that:1)During the historical period,the frequency and duration of CDHEs showed a non-significant increasing trend.The frequency and duration of CDHEs were the highest in July,at 0.511 times and 3.59 days,respectively.The frequency of mild CDHEs was the highest in the historical period,with an annual average frequency of 0.4 times,which mainly occurred in the middle and lower reaches of the Yangtze River Basin,the Hengduan Mountains,and the Yunnan-Guizhou Plateau.2)Among the 23 CMIP6 models,INM-CM4-8,ACCESS-ESM1-5,NESM3,NorESM2-LM,and INM-CM5-0 are the five most suitable models for the Yangtze River Basin after bias correction.3)In the future,the middle and lower reaches of the Yangtze River Basin will be the areas with high frequency and long duration of CDHEs,and the annual average frequency and duration of CDHEs by the NorESM2-LM model are the highest.The results of the five models and multi-modal ensemble also show small differences between scenarios in the short term and medium term and significant differences in the long term.In the long term of SSP5-8.5,the average annual frequency of CDHEs would increase by 2.3 times and 1.8 times,respectively,compared to the short term and medium term under the same scenario.The duration was 29.9 days and 21.3 days higher than that of SSP1-2.6 and SSP2-4.5 during the same period.The average annual frequency of mild CDHEs is the highest for all three scenarios,and all severity events should peak at SSP5-8.5.This findings can provide scientific and technical support to actively mitigate future climate change risks in the Yangtze River Basin.
Yangtze River Basincompound drought and heatwave eventsmagnitude indexCMIP6model evaluation
万方数据
维普
