祁连山地区过去500 a年代际旱涝事件演化及驱动因素分析

doi:10.12118/j.issn.1000－6060.2023.070

摘要/Abstract

摘要：

祁连山地区是气候变化敏感区和生态环境脆弱区，年代际重大干旱事件对其植被、冻土等生态要素影响显著。根据前人所重建的干湿变化数据集，分析了祁连山地区过去500 a年代际旱涝事件的发生规律、演化趋势及可能的驱动机制。结果表明：（1）祁连山地区近几十年来气候呈现明显的湿润化趋势，且1951年之后的变湿趋势已超出了历史时期自然变率范围。（2）亚洲夏季降水数据集对研究区历史干湿状况代表性良好，该地区过去7次年代际干旱事件降水差异显著，其中严重程度最高的是1786—1796年干旱；4次年代际湿润事件持续时间差异显著，持续时间最长的是发生在1968—2009年长达42 a的湿润事件。（3）年代际旱涝事件受气候外强迫和海温内部变率综合影响，太平洋和大西洋年代际海温模态变化及二者位相组合是调节祁连山年代际旱涝事件的关键因子。太阳辐射与祁连山降水呈同相位变化，火山活动则主要影响年代际干旱事件。研究强调长时间背景对评估当前祁连山地区气候异常的重要性，并建议评估未来该地区发生重大旱涝事件风险时需综合考虑外强迫和海温内部变率的不确定性。

关键词: 年代际旱涝, 小冰期, 气候驱动因素, 祁连山

Abstract:

Qilian Mountains is a climate-sensitive area in the arid areas of northwest China, where extreme megadrought events considerably impact vegetation, frozen soil, and other ecological elements. This paper uses three hydroclimate reconstruction datasets to analyze the occurrence, evolution, and possible driving mechanism of megadrought and pluvial events in the Qilian Mountains over the past 500 years. The results showed that the climate in the Qilian Mountains has shown a clear wetting trend since the recent decades, and the wetness trend after 1951 has exceeded the range of natural variability in the historical period. The RAP dataset provided a good representation of the historical dry and wet conditions in the study area. Significant variations were observed in precipitation during the past seven megadrought events in the region, with the highest severity occurring during the drought period of 1786—1796. Furthermore, considerable variations were noted in the duration of the four megapluvial events, with the longest duration being a wet event that lasted for 42 years from 1968 to 2009. Megadrought and pluvial events were influenced by climate forcing and internal variability of sea surface temperatures (SST). The decadal SST modes in the Pacific and Atlantic Oceans and their phase combinations were key factors regulating the megadrought and pluvial events in the Qilian Mountains. Solar radiation exhibited an in-phase variation with the precipitation in the Qilian Mountains, while volcanic activity primarily affected megadrought events. This study highlights the importance of a long-term perspective for assessing current hydroclimate anomalies in the Qilian Mountains and including possible roles of external forcing and sea surface temperature variability in assessing the future megadrought and pluvial risks in this region.

Key words: megadrought/pluvial events, Little Ice Age, driving factors, Qilian Mountain

任子健, 王江林, 徐贺年, 秦春. 祁连山地区过去500 a年代际旱涝事件演化及驱动因素分析[J]. 干旱区地理, 2024, 47(2): 214-227.

REN Zijian, WANG Jianglin, XU Henian, QIN Chun. Evolution and driving factors of megadrought and pluvial events in the Qilian Mountains during the past 500 years[J]. Arid Land Geography, 2024, 47(2): 214-227.

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数据集信息	RAP	MADA	IGGPRE
来源	Shi等^[31]	Cook等^[32]	Shi等^[33]
时间	1470—2013年	1300—2005年	1470—2000年
季节	6—8月	6—8月	5—9月
分辨率	2.0°×2.0°	2.5°×2.5°	0.5°×0.5°
代用指标	453个树轮年表71条DWI	327个树轮年表	372个树轮年表107条DWI
方法	DWI的水平变换与外推，树木年轮的PPR	PPR	PPR
范围	9.75°~56.25°N 60.25°~144.25°E	10.00°~57.50°N 60.00°~145.00°E	18.00°~54.00°N 72.00°~136.00°E

影响因素	来源	年份	代用指标
TSI	Lean^[37]	850—2016年	1610年以前：冰芯和树轮记录；1610—1882年：模型估计；1610年以后：观测记录
AOD	Crowley^[38]	1000—1998年	克里特岛和格陵兰岛的2个冰芯记录
PDO	Macdonald等^[39]	993—1996年	北美的2个树轮年表
AMV	Wang等^[40]	800—2010年	环北大西洋地区的46个气候代用记录

互相关	平滑前	平滑前1951—2000年	10 a平滑
RAP&IGGPRE	0.48^**	0.38^**	0.85^**
RAP&MADA	0.31^**	0.32^*	0.64^**

旱涝事件	RAP	IGGPRE	MADA
年代际干旱事件	1 1475—1500（26）	1475—1502（28）	1475—1500（26）
	2 1582—1591（10）	-	1585—1602（18）
	3 1622—1631（10）	-	-
	4 1634—1655（22）	1645—1659（15）	1645—1655（11）
	5 1683—1703（21）	1685—1730（46） 1685—1730（46）	-
	6 1706—1725（20）	1685—1730（46） 1685—1730（46）	1709—1719（11）
	7 1786—1796（11）	1788—1799（12）	-
	-	-	1919—1933（15）
年代际湿润事件	-	-	1526—1553（28）
	1 1560—1579（20）	1560—1583（24）	-
	-	-	1607—1621（15）
	-	-	1798—1812（15）
	2 1898—1910（13）	1887—1912（26）	-
	3 1938—1951（14）	1940—1952（13）	-
	4 1968—2009（42）	1966—1996（31）	1978—1992（15）

影响因素	回归分析		共线性分析
影响因素	回归系数	显著性	膨胀系数（VIF）
TSI	0.459	**	1.027
AOD	-0.012	-	1.194
PDO	0.088	*	1.068
AMV	0.185	**	1.187