近日，中国科学院大气物理研究所袁星研究员等对气候变化下2022年长江特大干旱进行了多尺度成因分析。2024年7月3日出版的《中国科学：地球科学》发表了这项成果。

研究人员简要概述了2022年夏季特大干旱的海洋和陆地因素，并估计了气候变化的风险。研究利用土壤湿度百分位数作为干旱指标，发现干旱在2个月内扩大到整个长江流域，8月底80%的流域处于严重干旱状态。2022年特大干旱的强度和发生速度都是过去62年来的第一次。重现期分别为86年和259年。综合分析结果表明，春季拉尼娜现象能促进长江流域从5-6月的湿润/正常状态向7-8月干旱状态的突变，有利于2022年突发性干旱强度和发生速度的增加。

线性回归分析还表明，这次前所未有的强度与太平洋年代际涛动的负相位相关。通过耦合强度指数量化土壤水分和水汽压亏缺，发现2022年7-8月长江流域存在较强的陆—气耦合。CMIP6气候模式的归因显示，在自然气候营力作用下，陆—气耦合使类似2022年的突发性干旱强度和发生速度的风险分别增加了61%±6%和64%±7%，而耦合和人为气候变化的协同作用使发生突发性干旱的风险分别增加了75%±22%和85%±12%。研究结果强调了陆地—大气耦合与人为气候变化在加剧突发性干旱中的作用。

据悉，2022年长江特大突发性干旱具有强度大、时空发展快等特点，并伴有持续的反气旋环流异常。然而，鉴于干旱的多尺度性质，这一极端事件的原因仍然令人难以捉摸。

附：英文原文

Title: Multiscale causes of the 2022 Yangtze mega-flash drought under climate change

Author: Xing YUAN, Yumiao WANG, Shiyu ZHOU, Hua LI, Chenyuan LI

Issue&Volume: 2024/07/03

Abstract: The 2022 Yangtze mega-flash drought is characterized by strong intensity and rapid development both in time and space, accompanied by a persistent anticyclonic circulation anomaly. However, the causes of the extreme event remain elusive given the multiscale nature of drought. Here we presented a brief overview for the oceanic and terrestrial causes of the mega-flash drought during the summer of 2022, and estimated the risk in a changing climate. Using the soil moisture percentile as the drought index, it was found that the drought expanded to the entire Yangtze River basin within two months, with 80% of basin under severe drought conditions at the end of August. Both the intensity and onset speed of the 2022 mega-flash drought were ranked as the first during the past 62years, with return periods of 86 and 259years, respectively. The results of composite analysis showed that the spring La Nia can facilitate the abrupt change from a wet/normal condition in May–June to drought in July–August over the Yangtze River basin, which was beneficial for the increase of flash drought intensity and onset speed in 2022. The analysis through the linear regression also indicated that the unprecedented intensity was associated with the negative phase of the Pacific Decadal Oscillation. Quantified by a coupling strength index for soil moisture and vapor pressure deficit, it was found that there was a strong land-atmosphere coupling over the Yangtze River basin during July–August 2022. The attribution by using CMIP6 climate models suggested that land-atmosphere coupling increased the risks of flash drought intensity and onset speed like 2022 by 61%±6% and 64%±7% under natural climate forcings, and the synergy of coupling and anthropogenic climate change would increase the risks by 75%±22% and 85%±12%. Our findings emphasized the role of land-atmosphere coupling combined with anthropogenic climate change in intensifying flash droughts.

DOI: 10.1007/s11430-024-1356-x

Source: https://www.sciengine.com/SCES/doi/10.1007/s11430-024-1356-x