双月刊

ISSN 1006-9895

CN 11-1768/O4

2020年6-7月西南地区东部降水异常偏多的水汽输送特征
作者:
作者单位:

1.重庆市气候中心;2.中国科学院大气物理研究所国际气候与环境科学中心;3.南京信息工程大学气象灾害省部共建教育部重点实验室

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基金项目:

国家自然科学基金项目41875111,国家重点研发计划项目2018YFE0196000


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

1.Chongqing Climate Center;2.International Center for Climate and Environment Sciences,Institute of Atmospheric Physics,Chinese Academy of Sciences;3.Key Laboratory of Meteorological Disaster,Ministry of Education,Nanjing University of Information Science Technology

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    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ECMWF的ERA5逐月再分析资料以及NCEP/NCAR提供的逐6h全球再分析资料,采用相关、回归、聚类、拉格朗日轨迹模式HYSPLITv5.0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前期冬季海温和青藏高原积雪的联系。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月对流层高、中、低层环流场配置是西南地区东部典型多雨的环流形势:200hPa上高空急流位置偏南,致使冷空气活动较多且偏南,同时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,而西太平洋副高明显西伸,有利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。采用欧拉方法计算的定性的水汽来源和采用拉格朗日方法计算的定量的水汽轨迹追踪结果,都表明2020年6-7月西南地区东部降水的水汽主要来自于孟加拉湾、南海和阿拉伯海等南方洋面的暖湿气流,而北方的干冷空气也有水汽向该区域输送,但相对于南方海洋的水汽输送要小得多。前冬青藏高原积雪偏多,印度洋和赤道中东太平洋海温偏高,引起孟加拉湾西风减弱,南海东风偏强,中南半岛北部南风偏强,形成西太平洋副高偏西偏强的典型风场特征,有利于孟加拉湾和南海地区水汽输送偏西偏强,中南半岛地区向北的水汽输送偏强,使得西太平洋副高西南侧的水汽能够源源不断输送到西南地区东部,造成该地区降水偏多。

    Abstract:

    In this paper, the anomalous characteristics of precipitation in the east of southwestern China (ESWC) in June-July,2020 and the related large-scale characteristics of water vapor transport, water vapor budget and water vapor source are analyzed by using correlation, regression, clustering, Lagrange trajectory model HYSPLITv5.0 simulation and other statistical methods based on the daily precipitation data of 118 stations and other reanalysis data. Then some indexes of water vapor intensity in key areas are defined, and the relationship between water vapor intensity in key areas and sea temperature and snow cover in Qinghai-Tibet Plateau in early winter is investigated. The results show that the average precipitation in the ESWC in June-July, 2020 is 50% more than that in normal year, which is the highest since 1961. Precipitation in most areas is obviously higher than that in normal year, except for some areas in central Guizhou and northeastern Sichuan. The configuration of tropospheric atmospheric circulation field in June-July, 2020 is a typical rainy circulation situation in the ESWC. at 200hPa, the position of the upper jet stream leans to the south, resulting in frequent and southern cold air activity. At the same time, the ESWC is located just south of the jet axis, with strong divergence outflow from the upper layer and strong convergence inflow from the lower layer, which provides 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 conductive to more precipitation in this region. The qualitative water vapor source calculated by Euler method and the quantitative water vapor trajectory tracking results calculated by Lagrange method both show that: the water vapor associated with precipitation in the ESWC in June-July, 2020 mainly comes from the warm and humid airflow in the southern ocean, such as Bay of Bengal, South China Sea and Arabian Sea, while the dry and cold air in the north also transports water vapor to this region, but the water vapor content is much smaller than that in the southern ocean. In the previous winter, the snow cover area of the Qinghai Tibet Plateau was relatively large, and the SST of the Indian Ocean and the equatorial Middle East Pacific was relatively high, resulting in the weakening of the west wind in the bay of Bengal, the strengthening of the east wind in the South China Sea, and the strengthening of the south wind in the northern part of the Indochina Peninsula. This feature is just the typical wind field feature of the strong and westward WPSH, which is beneficial to strengthening of the westward water vapor transport in the Bay of Bengal and the South China Sea, and the strengthening of northward water vapor transport in the Indochina Peninsula. This makes the water vapor in the southwest side of WPSH continuously be transported into the ESWC, resulting in more precipitation in this region.

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  • 收稿日期:2021-01-08
  • 最后修改日期:2021-05-16
  • 录用日期:2021-05-17
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