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李永华, 周杰, 何卷雄, 等. 2022. 2020年6~7月西南地区东部降水异常偏多的水汽输送特征[J]. 大气科学, 46(2): 309−326. doi: 10.3878/j.issn.1006-9895.2105.21002
引用本文: 李永华, 周杰, 何卷雄, 等. 2022. 2020年6~7月西南地区东部降水异常偏多的水汽输送特征[J]. 大气科学, 46(2): 309−326. doi: 10.3878/j.issn.1006-9895.2105.21002
LI Yonghua, ZHOU Jie, HE Juanxiong, et al. 2022. Characteristics of Water Vapor Transport Associated with Abnormal Precipitation over the East of Southwestern China in June and July 2020 [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(2): 309−326. doi: 10.3878/j.issn.1006-9895.2105.21002
Citation: LI Yonghua, ZHOU Jie, HE Juanxiong, et al. 2022. Characteristics of Water Vapor Transport Associated with Abnormal Precipitation over the East of Southwestern China in June and July 2020 [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 46(2): 309−326. doi: 10.3878/j.issn.1006-9895.2105.21002

2020年6~7月西南地区东部降水异常偏多的水汽输送特征

Characteristics of Water Vapor Transport Associated with Abnormal Precipitation over the East of Southwestern China in June and July 2020

  • 摘要: 利用1961~2020年西南地区东部118个气象站逐日降水量资料和1979~2020年欧洲中期天气预报中心(ECMWF)的ERA5逐月再分析资料以及美国气象环境预报中心和美国国家大气研究中心(NCEP/NCAR)提供的逐6 h全球再分析资料,采用相关、回归、聚类、混合单粒子拉格朗日综合轨迹(HYSPLITv5.0)模型模拟等方法对2020年6~7月西南地区东部降水异常偏多特征、大尺度水汽输送特征及水汽收支状况和主要水汽源地及贡献等进行了分析,定义了关键区水汽强度指标,分析了关键区水汽强度与海温的联系。结果表明,2020年6~7月西南地区东部平均降水量异常偏多5成,为1961年以来最多,除贵州中部和四川东北部的局部地区降水较常年略偏少外,其余地区降水均较常年明显偏多。2020年6~7月200 hPa上高空急流位置偏南,西南地区东部正好位于急流轴以南地区,高层强辐散流出,低层强辐合流入,配合从低层到高层的深厚的强烈的垂直运动,为降水提供了良好的动力条件,而西太平洋副热带高压(副高)明显西伸,有利于其西南侧的暖湿气流向西南地区东部输送,使得该区域降水偏多。采用拉格朗日方法计算的定量的水汽轨迹追踪结果表明2020年6~7月西南地区东部降水的水汽路径70.5%来自于孟加拉湾、南海和阿拉伯海等南方路径,17.6%来自于北方路径,11.9%来自于局地。前冬赤道中东太平洋海温偏高和热带印度洋全区海温偏高,西太平洋副高明显偏西、偏强,孟加拉湾和南海地区为东风距平,有利于南海地区向西的水汽偏强,不利于孟加拉湾地区向东的水汽输送;与此同时,菲律宾至我国南海附近为异常反气旋,使得中南半岛北部地区为偏南风距平,有利于中南半岛北部地区向北的水汽输送偏强,共同造成西南地区东部降水偏多。

     

    Abstract: This paper analyzes the anomalous characteristics of precipitation in the east of southwestern China (ESWC) during June–July 2020 and the related large-scale characteristics of water vapor transport, water vapor budget, and water vapor source using correlation, regression, clustering, hybrid single-particle Lagrangian integrated trajectory (HYSPLITv5.0) model simulation, and other statistical methods based on the daily precipitation data of 118 stations and other reanalysis data. Some indexes of the water vapor intensity in key areas are defined, and the relationship between the water vapor intensity in key areas and sea temperature is investigated. Results show that the average precipitation in the ESWC during June–July 2020 is 50% more than that in the normal year, which is the highest since 1961. Precipitation in most areas is obviously higher than that in the normal year, except for some areas in central Guizhou and northeastern Sichuan. The configuration of the tropospheric atmospheric circulation field during June–July 2020 is a typical rainy circulation situation in the ESWC. At 200 hPa, the position of the upper jet stream leans to the south, and the ESWC is located just south of the jet axis with a strong divergence outflow from the upper layer and a strong convergence inflow from the lower layer, providing favorable dynamic conditions for precipitation. In addition, the western Pacific subtropical high (WPSH) obviously extends westward, and the warm and humid airflow in the southwest side of the WPSH is transported to the ESWC, which is conducive to more precipitation in this region. The quantitative water vapor trajectory tracking results calculated by the Lagrange method show that there are 70.5% of the water vapor paths associated with precipitation in the ESWC during June–July 2020 from the southern routes such as the Bay of Bengal, the South China Sea, and the Arabian Sea, while 17.6% and 11.9% comes from the northern route and the local area, respectively. In the previous winter, the SST (Surface Sea Temperature) of the equatorial Middle East Pacific and the Indian Ocean was relatively high, the WPSH is obviously strong and westward, resulting in the east wind anomaly in the Bay of Bengal and the South China Sea, which is favorable for the westward water vapor transport in the South China Sea but unfavorable for the eastward water vapor transport in the Bay of Bengal. Meanwhile, the anomalous anticyclone from the Philippines to the South China Sea makes the south wind anomaly in the northern part of the Indo-China peninsula, which is conducive to the strong northward water vapor transport in this area. These together resulted in more precipitation in the ESWC.

     

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