1 四川省公路规划勘察设计研究院有限公司,成都 610041
2 中国科学院地理科学与资源研究所,陆地表层格局与模拟院重点实验室,北京 100101
3 中国科学院·水利部成都山地灾害与环境研究所,山地灾害与地表重点实验室,成都 610041
4 中国科学院青藏高原地球科学卓越创新中心,北京 100101
1 Sichuan Highway Planning, Survey, Design and Research Institute Ltd., Chengdu 610041, China
2 The Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
3 The Key Laboratory of Mountain Hazards and Surface Process, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences & Ministry of Water Conservancy, Chengdu 610041, China
4 Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China
作者简介 About authors
以1960年以来西藏境内已有记载的27次冰湖溃决灾害事件作为研究对象,基于西藏国家气象站点长时间序列（有效记录至今）日气温和日降雨数据,计算得到16个极端气温指数和6个极端降雨指数。通过主成分变换,提取综合极端气温指数和综合极端降雨指数,并进行历史（10年内对比）极端气候特征对比,获得冰湖溃决灾害发生当年及当月极端气候状态,结果表明西藏冰湖溃决灾害发生期（当年及当月）极端气候特征显著,反映极端气候状态对于激发西藏冰湖溃决灾害发生的重要贡献,具体表现为：(1) 67%（18次）的冰湖溃决事件发生当年综合极端气温指数和综合极端降雨指数均大于前期50%年份的综合极端气候指数,其中,13次灾害发生当年极端气候异常水平超过前期70%年份;(2)已有灾害暴发月份记载的25次冰湖溃决事件中,19次冰湖溃决事件发生当月极端气候指数异常偏高,11次冰湖溃决事件发生当月极端气温和极端降水均大于75%往年同期综合极端气候指数;(3)部分灾害事件如扎日错（1981年6月)、龙纠错溃决（2000年8月）等,灾害发生当年极端气温状态低于往年,而暴发当月综合极端气温指数和综合极端降雨指数均大于历史同期水平,表现为加剧状态;(4)所有冰湖溃决灾害发生当月的综合极端气温指数均高于往年同期指数,表明短历时极端气温事件对高原冰湖溃决灾害形成具有重要影响。关键词：冰湖溃决洪水;极端气候;全球变暖;西藏
以1960年以来西藏境内已有记载的27次冰湖溃决灾害事件作为研究对象,基于西藏国家气象站点长时间序列（有效记录至今）日气温和日降雨数据,计算得到16个极端气温指数和6个极端降雨指数。通过主成分变换,提取综合极端气温指数和综合极端降雨指数,并进行历史（10年内对比）极端气候特征对比,获得冰湖溃决灾害发生当年及当月极端气候状态,结果表明西藏冰湖溃决灾害发生期（当年及当月）极端气候特征显著,反映极端气候状态对于激发西藏冰湖溃决灾害发生的重要贡献,具体表现为：(1) 67%（18次）的冰湖溃决事件发生当年综合极端气温指数和综合极端降雨指数均大于前期50%年份的综合极端气候指数,其中,13次灾害发生当年极端气候异常水平超过前期70%年份;(2)已有灾害暴发月份记载的25次冰湖溃决事件中,19次冰湖溃决事件发生当月极端气候指数异常偏高,11次冰湖溃决事件发生当月极端气温和极端降水均大于75%往年同期综合极端气候指数;(3)部分灾害事件如扎日错（1981年6月)、龙纠错溃决（2000年8月）等,灾害发生当年极端气温状态低于往年,而暴发当月综合极端气温指数和综合极端降雨指数均大于历史同期水平,表现为加剧状态;(4)所有冰湖溃决灾害发生当月的综合极端气温指数均高于往年同期指数,表明短历时极端气温事件对高原冰湖溃决灾害形成具有重要影响。
关键词：冰湖溃决洪水;极端气候;全球变暖;西藏
In order to clearly understand the extreme climate background at the time of glacial lake outburst flood (GLOF) occurrence in high altitude mountain, we took 27 GLOF events recorded in Tibet since 1960 as samples. Based on the daily temperature data and the daily precipitation data recorded by these meteorological stations in the vicinity of the places where GLOF events occurred, 16 temperature extremes indices and 6 precipitation extremes indices were calculated in these places. By the method of Principal Component Analysis (PCA), a comprehensive extreme temperature index and a comprehensive extreme precipitation index were extracted, and the fluctuation of extreme climate in this period when the disaster occurred were obtained by compared the value of the comprehensive extreme climate index of the previous nine years on annual scale and monthly scale, respectively. The results showed that: (1) More frequent extreme temperature events and precipitation events appeared in the year when GLOF occurred by compared with the previous nine years on annual scale, which was validated in about 67% of GLOF events. (2) Among the 25 GLOF events with monthly outbreak time record, the monthly extreme temperature index and the monthly extreme precipitation index when disaster occurrence were more than 75% of that in the same period of previous nine years, which was validated in about 11 GLOF events. (3) The extreme climate events in several years when GLOF occurred were not very frequent, while both of the extreme temperature index and the extreme precipitation index on monthly scale were obviously higher than the same period of previous nine years, such as Zharicuo GLOF (June 1981), Longjiucuo GLOF (August 2000), Degacuo GLOF (September 2002), Ranzeria GLOF (July 2013) and the nameless lake (July 2015). (4) The monthly extreme temperature index of all GLOF events was higher than that of the same period of the previous nine years, which shows that the short-term extreme temperature events have an important impact on the formation of GLOF in high altitude mountain.Keywords：Glacial lake outburst flood (GLOF);Climate extremes;Global warming;Tibet
In order to clearly understand the extreme climate background at the time of glacial lake outburst flood (GLOF) occurrence in high altitude mountain, we took 27 GLOF events recorded in Tibet since 1960 as samples. Based on the daily temperature data and the daily precipitation data recorded by these meteorological stations in the vicinity of the places where GLOF events occurred, 16 temperature extremes indices and 6 precipitation extremes indices were calculated in these places. By the method of Principal Component Analysis (PCA), a comprehensive extreme temperature index and a comprehensive extreme precipitation index were extracted, and the fluctuation of extreme climate in this period when the disaster occurred were obtained by compared the value of the comprehensive extreme climate index of the previous nine years on annual scale and monthly scale, respectively. The results showed that: (1) More frequent extreme temperature events and precipitation events appeared in the year when GLOF occurred by compared with the previous nine years on annual scale, which was validated in about 67% of GLOF events. (2) Among the 25 GLOF events with monthly outbreak time record, the monthly extreme temperature index and the monthly extreme precipitation index when disaster occurrence were more than 75% of that in the same period of previous nine years, which was validated in about 11 GLOF events. (3) The extreme climate events in several years when GLOF occurred were not very frequent, while both of the extreme temperature index and the extreme precipitation index on monthly scale were obviously higher than the same period of previous nine years, such as Zharicuo GLOF (June 1981), Longjiucuo GLOF (August 2000), Degacuo GLOF (September 2002), Ranzeria GLOF (July 2013) and the nameless lake (July 2015). (4) The monthly extreme temperature index of all GLOF events was higher than that of the same period of the previous nine years, which shows that the short-term extreme temperature events have an important impact on the formation of GLOF in high altitude mountain.
Keywords：Glacial lake outburst flood (GLOF);Climate extremes;Global warming;Tibet
本文引用格式
编者按：
气候变化导致的灾害风险对人类社会产生广泛而深刻的影响,IPCC评估报告非常重视气候变化的灾害效应,专门于2012年发布了《管理极端事件和灾害风险推进气候变化适应特别报告》（SREX）。学术界越来越关注气候变化导致的灾害风险,为了集中展示这方面的成果,使学术界、社会和政策制定者更加关注气候变化对灾害及其风险的影响,本刊以“气候变化的灾害效应”为主题集中反映与气候变化相关的自然灾害及其风险方面的最新研究成果,主要内容有：青藏高原对气候变化敏感的高寒区冰湖溃决发生的极端气候特征,气候变化背景下极端天气气候事件与地震作用遭遇条件下地质灾害的活动特征,气候变化对泥石流危险性的影响,全球热浪人口暴露特征,以及以2016武汉暴雨洪涝灾害为例分析灾害经济影响的跨区域波及效应。希望能在气候变化对气象灾害、地质灾害、水文灾害、山地灾害等灾种形成条件、活动规律、危害特征及其社会经济影响评估等方面提供新的认识,供研究气候变化与自然灾害关系的同仁参考和指正。
因此,本文从不同时间尺度下的极端气候特征入手,分别从长期和短期极端天气气候变化对西藏冰湖溃决灾害形成的影响进行分析,并归纳总结不同时间尺度下利于西藏冰湖溃决灾害形成的极端气候特征类型,为高原山区山地灾害研究提供新思路。
拥有“世界屋脊”和“第三极”称号的青藏高原是世界上海拔最高的高原,平均海拔超过4500 m,同时也是发育最年轻的高原。青藏高原地域辽阔,地势高亢,具有独特多样的环境气候条件,是世界上一个独具特色的地理单元和气候变化的敏感区与放大器。活跃的地质构造、巨大的地形高差和特殊的气候条件,使得青藏高原成为冰湖溃决灾害的典型发育区。
图11930年以来西藏地区溃决冰湖空间分布
Fig. 1Distribution of the glacial lake outburst flood (GLOF) events in Tibet since 1930
附表1930年以来西藏冰湖溃决事件
Appendix The GLOF events in Tibet since 1930
注：表中数据来自于文献[15,17,20-30]。
文章分别对16个极端气温指数和6个极端降雨指数进行主成分变换,利用主成分变换后的综合极端气温指数（Yt）和综合极端降雨指数（YP）对西藏冰湖溃决灾害的极端气候变化特征进行分析。
式中,Xi为各极端气温指数,Xj为各极端降雨指数,ki为各极端气温指数计算系数,kj为各极端降雨指数计算系数。
冰湖溃决是由冰湖水位、母冰川冰舌形态及危险冰体分布、坝体结构强度等多方面因素综合作用形成的灾害事件。天气气候作为冰湖溃决重要的激发因素,其变化直接影响到冰湖水位、危险冰体、坝体结构强度等致灾因素的变化。为了剖析极端气候变化对冰湖溃决灾害致灾环境因素的影响,文章分别从年、月等不同时间尺度着手,重点分析灾害发生时期与前期（10年内）同一区域极端气候特征的对比状态。综合极端气候指标若为正值,则表明该年或该月份极端气候相对于这10年异常偏高,反之则异常偏低。
图2西藏境内GLOF事件发生当年极端气候特征类型
注：(a)为极端气温与极端降水均异常偏高状态（以1988年光谢错溃决为例);(b)为仅极端降雨指数偏高状态（以2000年龙纠错溃决为例);(c)为仅极端气温偏高状态（以1982年金错溃决为例)。
Fig. 2The three state types of extreme climate in the year when GLOF occurred
表1各溃决冰湖发生当年的极端气温状态及前期9年对比偏离程度
Table 1 The state of extreme climate in the year when GLOF occurred by compared with nine years before
注：偏离程度>0.5则表明综合极端指数值高于50%年份的极端气候水平,<-0.5表明综合极端指数值低于50%年份的极端气候水平。
图3西藏境内GLOF事件发生当月极端气候特征类型
注：(a)为极端气温与极端降水指数均异常偏高（以2000年8月龙纠错溃决为例);(b)为仅极端气温指数偏高（以1982年8月金错溃决为例)。
Fig. 3The two state types of extreme climate in the month when GLOF occurred by compared with the same period in previous nine years
表2各溃决冰湖发生当月的极端气温状态及前期9年同期对比偏离程度
Table 2 The state of extreme climate in the month when GLOF occurred by compared with the same period in previous nine years
图4西藏境内GLOF事件发生当年及当月极端气候状态统计图
Fig. 4The state of extreme climate in the month and the year when GLOF occurred by compared with the same period in previous nine years
冰湖溃决是由地震、天气气候、冰湖水位状况、母冰川冰舌形态及危险冰体分布、坝体形态及结构强度等多方面因素综合作用形成的灾害事件,其中,地震和气象要素为高原冰湖溃决灾害发生的重要激发因素,如地震造成冰川直接断裂、地震造成坝体结构破坏、天气气候影响冰舌及冰碛坝体内埋藏冰消融状态及冰湖周边水环境状态,其中地震往往直接致灾。
文章以1960年以来西藏境内已有记载的27次冰湖溃决灾害事件作为研究对象,提取灾害事件发生期（当年及当月）与往期的综合极端气候指数。并通过历史同期不同时间尺度（年、月）对比,获得冰湖溃决灾害发生当年及当月极端气候状态,结果显示大多数灾害发生时期（当年或当月）的极端气候表现出异常偏高状态,表明灾害发生时期,冰湖所在区域经历较为严重的极端气温或极端降水事件。从1960年至今27次西藏冰湖溃决事件成因来看（附表),明确灾害成因的有22次,其中,20次由于冰舌末端临近湖体的冰体发生断裂,形成冰崩或冰滑坡,进而造成冰湖溃决灾害;1次（浪错）由于强降水（极端降雨）过程形成溃决灾害;1次（给曲冰湖）由冰崩和强降水共同作用造成冰湖溃决。说明已统计的冰湖溃决事件中,大多数灾害受气象条件的快速激发影响,同样说明已有记载的西藏大型冰湖溃决灾害事件受极端气候致灾影响明显。
由于西藏冰湖溃决事件发生于较高海拔,且多数处于无人区域,导致灾害事件过程记录的完整性及准确性难以保障,为了尽量减少灾害记录错误,笔者在查阅多个文献及史料基础上,统计得到文中灾害数据。此外,由于西藏高原地域广阔,大多地区并无实际气象观测资料,特别是针对冰湖所处高海拔山区的监测数据。为了尽量准确描述灾点区域的天气气候状况,文章利用区域气候插值方法,根据冰湖坐标,计算获得相应位置的长时间气象数据,并基于此进行灾害事件发生期的极端气候状态分析,所得结果可信度相对较高。
冰湖溃决灾害是西藏较为典型的山地灾害类型之一,导致溃决灾害的发生主要由于特殊的高原环境因素（如冰舌形态、冰湖水位、坝体结构稳定性等）和高原天气气候相互作用的结果。除地震影响以外,西藏冰湖溃决灾害是在长期气候环境及短期气象条件的共同影响下,造成冰湖水位、坝体结构强度、临近区域冰舌形态等环境发生变化,进而造成灾害。分析结果反映出极端气候状态对于激发西藏冰湖溃决灾害发生的重要贡献,能够为进一步深化高寒山区冰湖溃决灾害形成机理的定量化研究提供帮助。
青藏高原:全球气候变化的驱动机与放大器 I.新生代气候变化的基本特征
Qinghai-Tibetan Plateau: a driver and amplifier of global climatic changes. I. Basic characteristics of climatic changes in Cenozoic Era
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Climate changes in the Tibetan Plateau during the last three decades
青藏高原区域气候变化及其差异性研究
Climate change and its regional differences over the Tibetan Plateau
Spatial variability and potential impacts of climate change on flood and debris flow hazard zone mapping and implications for risk management
The two main mechanisms of glacier lake outburst flood in Tibet, China
气候变暖背景下青藏高原山地灾害及其风险分析
Risk analysis of mountain hazards in Tibetan Plateau under global warming
Mountain hazards in the Tibetan Plateau: research status and prospects
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近20 a来西藏朋曲流域冰湖变化及潜在溃决冰湖分析
Glacial lakes variation and the potentially dangerous glacial lakes in the Pumqu basin of Tibet during the last two decades
藏东南冰湖溃决泥石流灾害及其发展趋势
Hazards of debris flow due to glacier-lake outburst in southeastern Tibet
1980—2007年喜马拉雅东段洛扎地区冰湖变化遥感研究
Monitoring glacial lake variations based on remote sensing in the Lhozhag district eastern Himalayas, 1980-2007
西藏冰湖溃决主要特征
Characteristics of glacier lake breaks in Tibet
西藏终碛堤冰湖溃决冰川、温度条件的初步研究
Preliminary study on the glacial and temperature conditions of terminal moraine dam glacier lake outburst in Tibet
以气温和降雨量为指标的冰湖溃决预警方法
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1961—2010年西藏极端气温事件的时空变化
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Extreme weather and climate changes and its environmental effects over the Tibetan Plateau
西藏喜马拉雅山区危险冰湖及其溃决特征
Dangerous glacial lake and outburst features in Xizang Himalayas
20世纪以来西藏冰湖溃决灾害事件梳理
Study on the glacial lake outburst flood events in Tibet since the 20th century
喜马拉雅山地区冰川湖溃决灾害隐患遥感调查及影响因素分析
Remote sensing investigation and influence factor analysis of glacier lake outburst potential in the Himalayas
西藏波密米堆冰湖溃决浅议
Bursting of the Midui moraine lake in Bomi, Xizang
聂拉木县冲堆普2002年泥石流成因分析及防治对策
Debris flows of Chongdui gully in Nyalam county, 2002: cause and control
气温对西藏冰湖溃决事件的影响
Impact of temperature on glacier-lake outbursts in Tibet
2013年西藏嘉黎县“7·5”冰湖溃决洪水成因及潜在危害
The cause and potential hazard of glacial lake ooutburst flood occurred on July 5, 2013 in Jiali county, Tibet
波曲流域冰湖及其溃决灾害链特征分析
Investigation of loess collapsible cracks around the Datonghe-Qinwangchuan diversion project
冰碛湖溃决泥石流流量计算方法
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