| 东亚和南亚季风协同作用对西南地区夏季降水的影响 |
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| 引用本文： | 王映思,肖天贵,董雪峰,李勇,赵平.东亚和南亚季风协同作用对西南地区夏季降水的影响[J].气象学报,2021,79(4):541-557. |
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| 作者姓名： | 王映思 肖天贵 董雪峰 李勇 赵平 |
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| 作者单位： | 1.成都信息工程大学，成都，610225 |
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| 基金项目： | 第二次青藏高原综合科学考察研究项目（2019QZKK010408）、灾害天气国家重点实验室项目（2019LASW-B02）、气象预报业务关键技术发展专项（YBGJXM2020-04-01） |
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| 摘 要： | 为探究东亚夏季风（EASM，East Asian summer monsoon）和南亚夏季风（SASM，South Asian summer monsoon）相互作用及其强弱变化对西南地区夏季降水的影响，利用1979—2019年西南地区161站逐日降水观测资料和ERA-5提供的1979—2019年全球再分析资料，通过对比西南地区夏季标准化降水指数与东亚和南亚夏季风强度指数的相关，提出了东亚夏季风和南亚夏季风的4类协同作用，并分析了4类季风协同作用对西南地区降水的影响。结果表明:（1）EASM和SASM存在强EASM-强SASM、强EASM-弱SASM、弱EASM-弱SASM和弱EASM-强SASM 4类季风协同作用，其对应的协同年降水特征分别为四川盆地西部型、西南全区一致型、四川全盆地型及西南东部型。（2）强EASM-强SASM年，西太平洋副热带高压偏东偏弱，伊朗高压偏西偏弱，印度半岛东北部与中国南海存在两个气旋式环流，EASM将中国南海—西太平洋的水汽输送至西南地区，西南地区整体水汽辐合较弱，多下沉运动，降水较少，成都平原存在较明显的水汽辐合，上升运动明显，降水较多。强EASM-弱SASM年，西太平洋副热带高压偏东偏弱，伊朗高压偏东偏强，反气旋式环流与气旋式环流位于印度半岛南部与西太平洋，EASM将中国南海—西太平洋的水汽输送至西南地区，西南地区有明显的水汽辐合和上升运动，降水较多。弱EASM-弱SASM年，西太平洋副热带高压西伸与东伸的伊朗高压打通，低纬度地区无明显的环流圈，孟加拉湾西侧水汽向北输送至四川盆地，并伴有明显的上升运动，其余地区水汽辐散，气流下沉，降水较少。弱EASM-强SASM年则与强EASM-弱SASM年基本相反。
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| 关 键 词： | 东亚夏季风 南亚夏季风 协同作用 西南地区 夏季降水 |
| 收稿时间： | 2021/1/4 0:00:00 |
| 修稿时间： | 2021/5/1 0:00:00 |
Influence of East Asian monsoon and South Asian monsoon synergy on summer precipitation in Southwest China |
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| WANG Yingsi,XIAO Tiangui,DONG Xuefeng,LI Yong,ZHAO Ping.Influence of East Asian monsoon and South Asian monsoon synergy on summer precipitation in Southwest China[J].Acta Meteorologica Sinica,2021,79(4):541-557. |
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| Authors: | WANG Yingsi XIAO Tiangui DONG Xuefeng LI Yong ZHAO Ping |
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| Institution: | 1.Chengdu University of Information Technology，Chengdu 610225，China2.Chinese Academy of Meteorological Sciences，Beijing 100081，China3.National Meteorological Centre，Beijing 100081，China |
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| Abstract: | In order to explore the interaction between the East Asian summer monsoon (EASM) and the South Asian summer monsoon (SASM) and its influence on summer precipitation in Southwest China, daily precipitation observations collected at 161 stations in Southwest China from 1979 to 2019 and the global reanalysis data of ERA-5 from 1979 to 2019 are used to compared the correlations of the standardized precipitation index in Southwest China with the intensity indexes of the East Asian and South Asian summer monsoons. Four types of monsoon synergy between EASM and SASM are proposed, and the influences of the four types of monsoon synergy on the precipitation in Southwest China are analyzed. The results show that: (1) There are four types of monsoon synergy in EASM and SASM: Strong EASM-strong SASM, strong EASM-weak SASM, weak EASM-weak SASM and weak EASM-strong SASM. The corresponding cooperative annual precipitation characteristics are the western Sichuan basin type, the whole Southwest consistent type, the whole Sichuan basin type and the eastern Southwest type. (2) In strong EASM-strong SASM years, the western Pacific subtropical high is weaker than normal and shifts to the east, the Iranian high is weaker than normal ad shifts to the west, and there are two cyclonic circulations located in the northeast of the Indian Peninsula and the South China Sea, respectively. The EASM transports water vapor from the South China Sea and the western Pacific to Southwest China. The water vapor convergence in Southwest China is weak with more descending motions and less precipitation. However, there exist obvious water vapor convergence and ascending motions in Chengdu Plain, leading to more precipitation there. In the strong EASM-weak SASM years, the western Pacific subtropical high is weaker and shifts to the east, and the Iranian high is stronger and located to the east of its normal position. The anticyclonic circulation and cyclonic circulation are located in the south of the Indian Peninsula and the western Pacific, respectively. The EASM transports water vapor from the South China Sea and the western Pacific to Southwest China. Significant water vapor convergence and upward movement develop in the southwest, resulting in more precipitation. In weak EASM-weak SASM years, the western Pacific subtropical high extends westward and connects with the Iranian high that extends eastward, while there is no obvious circulation loop in the low latitudes. Water vapor in the west of the Bengal Bay is transported northward to Sichuan Basin, accompanied by obvious upward movements. In other areas, water vapor is divergent with sinking air flow, and precipitation is less than normal. In the weak EASM-strong SASM years, the situation is basically opposite to that in the strong EASM-weak SASM years. |
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| Keywords: | East Asian summer monsoon South Asian summer monsoon Synergy effect Southwest China Summer precipitation |
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