过去600年中国西南地区极端旱涝事件的重建与分析

RECONSTRUCTION AND ANALYSIS OF EXTREME DROUGHT AND FLOOD EVENTS IN SOUTHWEST CHINA IN THE PAST 600 YEARS

以历史文献为主要资料,采用百分位阈值法重建了过去600年(1400~2000年)中国西南地区发生概率为10%的极端旱涝事件序列,发现:1700年是西南地区极端旱涝事件的转折点,之前极端干旱年份多于极端洪涝年份,之后极端洪涝年份多于极端干旱年份。现代暖期,极端旱涝事件发生频率与强度偏高,但皆未超过历史时期的峰值。在偏暖湿时,极端旱涝事件偏少,极端洪涝年多于极端干旱年;在偏冷干时,极端旱涝事件均较多,极端干旱年发生概率高于极端洪涝年;在小冰期和现代暖期内极端旱涝事件有不同的冷暖对应模式。西南地区极端旱涝事件的发生与亚洲季风有着密切的关系,且南亚夏季风的影响更为突出,1700年前后极端旱涝事件的转折对应了南亚夏季风的转折。南亚夏季风偏强时,极端旱涝事件偏少且极端洪涝事件发生概率高于极端干旱事件,南亚夏季风偏弱时则反之。ENSO在年际尺度上对极端旱涝事件发生有重要影响。PDO在年代际和多年代际尺度上通过影响亚洲季风,进而影响到西南地区极端旱涝事件。

In the research field of Chinese historical climate,historical documents play an irreplaceable role because of their relatively clear physical mechanism and high spatial-temporal resolution.The materials of this paper were mainly historical documents,including official history,local chronicles,anthologies,archives,inscriptions and other historical materials.The spatial range of this paper is Southwest China(31°~21°N,97°~111°E),which is affected by the South Asian monsoon and East Asian monsoon,and the time range spans the Little Ice Age and the Modern Warm Period.This study reconstructed the extreme drought and flood events in Southwest China in the past600 years(1400~2000 A.D.)by using the Drought and Flood Grade Method and the Percentile Threshold Method.The research showed that:1700 A.D.was the turning point of extreme drought and flood events.Before 1700 A.D.,there were more extreme drought events than extreme flood events,while there were more extreme drought events after 1700 A.D.In the Modern Warm period,the frequency and intensity of extreme drought and flood events were at high level,but they did not exceed the peak in the past 600 years.When the area was warm and wet,extreme drought and flood events were less,while the former ones were less than the later,The distribution of extreme drought and flood events had different corresponding patterns between the Little Ice Age and the Modern Warm period.The occurrence of extreme events in Southwest China is closely related to the Asian monsoon,and the influence of the South Asian summer monsoon is more prominent.The turning point of extreme events in 1700 A.D.corresponds to the turning point of the South Asian summer monsoon.When the South Asian summer monsoon was strong,the extreme events were less and the probability of extreme flood events was higher,and vice versa.ENSO played an important role on the interannual scale.PDO influenced extreme drought and flood events in Southwest China on the decadal and multigenerational scales by influencing the Asian monsoon.This study could be helpful to understand the response of regional climate to climate change and the impact of Asian monsoon system on regional extreme drought and flood events.