南京师范大学Yan Mi与Liu Jian等合作研究团队在最新研究中，报道了全新世东亚副热带西风急流与东亚夏季风在不同时期的共同演化，及其对中国降水格局的影响。2025年2月24日出版的《中国科学：地球科学》杂志发表了这项成果。

一般认为，东亚副热带西风急流（EASWJ）与东亚夏季风（EASM）的相互作用，是影响中国降水模式演变的关键动力因素。利用末次极大期以来的瞬态气候演化模拟结果，应用多元经验正交函数（MVEOF）分析方法，研究人员分析了全新世早、中、晚三个时期EASWJ和EASM的协同演化关系，及其对中国降水格局的影响。结果表明，全新世不同时段的第一次MVEOF模态，在东亚季风强度异常上均表现出非相位关系。

然而，在全新世晚期，急流变得更宽、更倾斜。在它们共同演化过程中形成的二次环流的影响下，中国东部在全新世早期和中期表现为南北走向的“南涝北旱”或“南旱北涝”的偶极型降水，而中国北方则表现为东西走向的“西湿东干”或“东湿西干”的偶极型降水。而在全新世晚期，整个地区呈现区域一致的降水格局。在此模式下，全新世中晚期的降水主要以趋势变化为主。第二次MVEOF模态表明，全新世早期东亚副热带东移和急流蒸汽轴缩短导致东亚季风减弱，导致中国东部呈现南北偶极降水模式，华北呈现区域一致降水模式。

全新世中期，东西副热带北上，东西副热带增强时，中国东部和华北地区均出现了双极降水模式，而华北地区的水汽状况不明显，反之亦然。在全新世晚期，东亚副热带和东亚副热带的强度异常在温带呈非同相关系，在亚热带呈同相关系，导致中国东部呈三极降水模式，在华北呈偶极降水模式。在此模式下，全新世中晚期的降水主要以百年振荡为主。受EASWJ和EASM共同演化关系影响的降水模式与重构降水资料吻合较好，从动力机制角度解释了重构资料中观测到的降水模式。

附：英文原文

Title: The co-evolution of East Asian subtropical westerly jet and East Asian summer monsoon during different time periods in the Holocene and its influence on precipitation patterns in China

Author: Yawen LIU, Mi YAN, Jian LIU, Sumin WANG, Zhengyu LIU, Liang NING, Ziyi WANG

Issue&Volume: 2025/02/24

Abstract: Generally, the interaction between the East Asian subtropical westerly jet (EASWJ) and the East Asian summer monsoon (EASM) is regarded as a critical dynamic factor in the evolution of precipitation patterns in China. Using simulation results from the transient climate evolution since the last glacial maximum, this study applies the multivariate empirical orthogonal function (MVEOF) analysis method to investigate the co-evolution relationships of the EASWJ and the EASM during the early, middle, and late Holocene, as well as their influence on precipitation patterns in China. The results indicate that all the first MVEOF modes in different time periods of the Holocene display an out-of-phase relationship in the intensity anomaly between the EASWJ and the EASM. However, the jet stream is wider and more tilted in the late Holocene. Under the influence of secondary circulations formed during their co-evolution, a north-south dipolar precipitation pattern in eastern China (“flood in the south and drought in the north” or “drought in the south and flood in the north”) and an east-west dipolar pattern in northern China (“wet in the west and dry in the east” or “wet in the east and dry in the west”) are found in the early and middle Holocene, while in the late Holocene a regionally-consistent precipitation pattern is witnessed across the whole region. In this mode, the precipitation in the middle and late Holocene is primarily dominated by trend changes. The second MVEOF mode reveals that the EASM weakens when the EASWJ shifts eastward and the jet steam axis shortens during the early Holocene, resulting in a north-south dipolar precipitation pattern in eastern China and a regionally-consistent pattern in northern China. In the middle Holocene, dipolar precipitation patterns are also observed in both eastern China and northern China when the EASWJ moves northward and the EASM strengthens, while the moisture condition in North China is less pronounced, and vice versa. In the late Holocene, the intensity anomalies of the EASWJ and the EASM exhibit an out-of-phase relationship in the temperate zone and an in-phase relationship in the subtropical zone, leading to a tripolar precipitation pattern in eastern China and a dipolar pattern in northern China. In this mode, the precipitation during the middle and late Holocene is primarily dominated by centennial oscillations. The precipitation patterns influenced by the co-evolution relationship between EASWJ and EASM correspond well with the reconstructed precipitation data, providing an explanation for the precipitation patterns observed in the reconstructed data from the perspective of dynamical mechanisms.

DOI: 10.1007/s11430-024-1505-3

Source: https://www.sciengine.com/SCES/doi/10.1007/s11430-024-1505-3