Influences of Lateral Boundary Forcings on the 2020 Extreme Meiyu in the Yangtze‐Huaihe River Valley
Influences of Lateral Boundary Forcings on the 2020 Extreme Meiyu in the Yangtze‐Huaihe River Valley
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DOI：
10.1029/2023jd038836
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发表时间：
2023-09
期刊：
影响因子：
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通讯作者：
Xiaoyu Zhu;Yijia Hu;Xuguang Sun;Zhong Zhong-Zhong;Y. Ha;Yunying Li
中科院分区：
文献类型：
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作者：
Xiaoyu Zhu;Yijia Hu;Xuguang Sun;Zhong Zhong-Zhong;Y. Ha;Yunying Li
江淮流域每年夏季都有梅雨。它的强度、分布和季节内变化受来自不同方向的大气强迫的影响很大，如来自南方的季风西南风、东部的西太平洋副热带高压、北部的大气长波活动和来自西部的西南涡等。利用区域气候模式4.6（RegCM4.6）研究了不同方向的大气强迫对2020年极端梅雨的贡献。一系列的敏感性实验进行了现实或气候平均的侧边界条件。结果表明，南方季风西风带向黄海高分辨率云系输送水汽和热量，与北方频繁的大气长波活动带来的冷空气交汇，形成了这次极端梅雨。频繁的北方冷空气可以抬升暖空气，提供不稳定条件，使降水分布类似于东亚地区的遥相关型。东部稳定的西太平洋副高将2020年梅雨带长期锚定在YHTV上。此外，不同方向的大气强迫对2020年梅雨演变的贡献随时间变化。6月10日以前，东部的西太平洋副热带高压对梅雨演变的贡献最大。6月11日至7月3日，南、北大气强迫的联合作用占主导地位。7月3日至10日，北方冷空气起主要作用。
Meiyu occurs in Yangtze‐Huaihe River valley (YHRV) every summer. Its intensity, distribution, and intraseasonal variation are greatly influenced by atmospheric forcings from different directions, such as the monsoon southwesterlies from the south, the western Pacific subtropical high (WPSH) in the east, the atmospheric longwave activities in the north, the southwest vortex from the west, and so on. In this study, to explore the contributions of the atmospheric forcings from different directions to 2020 extreme Meiyu, Regional Climate Model version 4.6 (RegCM4.6) is employed. A series of sensitivity experiments are conducted with realistic or climatological averaged lateral boundary conditions. The results show that the monsoon westerlies from the south transport moisture and heat to YHRV, converge with the cold air brought by the frequent atmospheric longwave activities in the north, and result in this extreme Meiyu. The frequent cold air from the north can lift warm air, provide unstable conditions, and make the distribution of precipitation similar to the teleconnection pattern in East Asia. The stable WPSH in the east anchors the 2020 Meiyu rainband to the YHTV for a long time. In addition, the contributions of the atmospheric forcings from different directions to evolution of 2020 Meiyu change with time. Before 10 June, the WPSH in the east mainly contributes to the Meiyu evolution. From 11 June to 3 July, the combined effects of atmospheric forcings from the south and north are dominant. From 3 July to 10 July, the cold air from the north plays a major role.