双月刊

ISSN 1006-9895

CN 11-1768/O4

青藏高原冬季绕流的变化特征及其对中国气候的影响
作者:
作者单位:

1.成都信息工程大学大气科学学院,高原大气与环境四川省重点实验室;2.兰州大学大气科学学院;3.河北省人工影响天气办公室

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基金项目:

国家自然科学基金


Variation Characteristics of the Westerly flow around the Tibetan Plateau in Winter and its Impact on Climate in China
Author:
Affiliation:

1.School of Atmosphere Science,Chengdu University of Information Technology,Plateau Atmosphere and environment Key Laboratory of Sichuan Province;2.School of Atmosphere Science,Lanzhou University;3.Hebei Province Weather Modification Office

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    摘要:

    利用1979~2019年NCEP/NCAR再分析资料和中国地面基本气象要素日值数据集(V3.0)的气温和降水资料,首先定义了客观表征冬季青藏高原南北两支绕流变化的指数,然后分析了其不同的变化特征,并采用相关分析、合成分析等方法初步研究了青藏高原南北两支绕流异常变化对中国气温和降水的影响机制。主要结果有:(1)青藏高原冬季北支绕流和南支绕流之间存在明显的不同变化特征。北支(南支)绕流异常强、南支(北支)绕流异常弱时,对流层中低纬度地区从高原西部到我国东部沿岸为一个大范围的异常反气旋式(气旋式)环流系统,高原中部的500hPa为一个异常反气旋(气旋)环流中心,并垂直延伸到300hPa高度(随高度向西北方向倾斜);南北两支绕流变化呈显著的负相关。(2)青藏高原冬季南北两支绕流的异常变化对我国冬季天气气候有显著影响。当青藏高原北支绕流强(弱)时,我国除东北地区气温偏低(高)、降水偏多(少)外,河套、青藏高原及长江以南地区气温偏高(低)、降水偏少(多);当南支绕流强(弱)时,全国气温普遍偏低(高),东北及新疆北部地区降水偏少(多),西南及南方大部分地区降水偏多(少)。(3)综合分析东亚对流层整层大气要素的垂直结构异常变化对我国天气气候异常的影响表明:当青藏高原北支绕流强、南支绕流弱时,35°N以北的整个对流层中都是异常西风,35°N以南850hPa以上都是异常东风,我国东部对流层大气是受青藏高原纬向异常绕流影响的“正压结构”;相应的对流层中850hPa以下底层从南到北为一致的异常西南风,850hPa以上为35°N北侧异常西北风与南侧异常东北风之间反气旋式切变、下沉运动异常,300hPa以下异常偏暖,这些不利于冷空气南下和反气旋切变加强的下沉运动增温作用,导致了我国东部大部分地区气温偏高、降水偏少。当青藏高原南支绕流强、北支绕流弱时,对流层中的纬向风异常则为明显的“斜压特征”,异常西风呈现为从对流层低层到高层、低纬度到高纬度的倾斜的带状特征,其下方自华南地区近地面到华北200hPa高度为“三角形”状的异常东风,配合相应的经向风异常、华南到华北的异常上升运动,低层为“三角形”状的异常冷气团向南切入到我国南海地区,中上层为异常偏暖的西南气流在冷气团上自南向北爬升到我国中高纬度地区,导致我国大范围的气温异常偏低、降水偏多。

    Abstract:

    Using the NCEP/NCAR reanalysis data from 1979 to 2019 and the temperature and precipitation of the daily data set of basic meteorological elements in China (V3.0), the indexes that objectively characterizes the changes of the northern and southern branch westerly flows around the Tibetan Plateau in winter are defined firstly. And then, the different characteristics of their changes are analyzed, and the influence mechanism of the abnormal changes of the two branch flows around Tibetan Plateau on the temperature and precipitation in China is preliminarily studied by means of correlation analysis and composite analysis. The main results are: (1) There are obvious different characteristics of changes between the northern and southern branch westerly flows around Tibetan Plateau in winter. When the northern branch (southern branch) flow is stronger and the southern branch (northern branch) flow is weaker, there is a large-scale anomalous anticyclone (cyclone) circulation system from the western Tibetan Plateau to the eastern coast of China in the middle-low latitudes of troposphere, and the central Tibetan Plateau is an anomalous anticyclone (cyclone) system center over 500hPa, which extends vertically to the height of 300hPa (inclining to the Northwest with the altitude). There is a significant negative correlation between the north and the south branch westerly flows of the troposphere. (2) The anomalous changes of the south/north branch westerly flows around Tibetan Plateau in winter have a significant impact on the winter weather and climate in China. When the northern branch flow of the Tibetan Plateau is stronger (weaker), the Hetao, Tibetan Plateau and the South China have relatively higher (lower) temperature and less (more) precipitation, but the lower (higher) temperature and more (less) precipitation in Northeast China. However, when the southern branch flow is stronger (weaker), the temperature is generally lower (higher) in the whole China, the precipitation is less (more) in northeastern China and northern Xinjiang, the more (less) precipitation in most parts of southwestern and southern China. (3) A comprehensive analysis the abnormal changes of the vertical structure of atmospheric elements over the East Asian troposphere influence on the China weather and climate anomalies shows: when the northern branch flow is stronger corresponding to the weaker southern branch flow, there are abnormal westerlies in the troposphere to the northern area of 35°N, and abnormal easterly winds above 850hPa to the southern area. The troposphere atmosphere over eastern China affected by the abnormal zonal flows around the Tibetan Plateau of the "Barotropic structure". The corresponding troposphere below 850hPa has a consistent anomalous southwest wind from southern to northern areas, the anticyclonic shear between the anomalous northwest wind and northeast wind above 850hPa in near 35 ° N, the abnormal descending motion and the warmer below 300hPa, these conditions are not conducive to the cold air southward movement and the anticyclone shear enhanced the effect of subsidence motion on temperature increase, as a result, the temperature is higher and the precipitation is less in most areas of eastern China. On the contrary, when the southern branch flow is stronger corresponding to the weaker northern branch flow, the abnormal zonal wind in the troposphere is an obvious "Baroclinic feature", and the anomalous westerly wind shows a slope zonal feature from lower to upper troposphere and from low latitude to high latitude. The Abnormal easterly wind of the lower troposphere is "triangle shaped 200hPa of North China, matching the meridional wind anomaly and the abnormal ascending movement from South China to North China, the "triangle shaped" abnormal cold air mass cuts southward into the South China Sea in the lower layer, the warmer southwest airflow climbs from south to north over the cold air mass to the middle and high latitudes in the upper layer, resulting in a large range of abnormally lower temperature and more than precipitation in China.

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  • 收稿日期:2020-12-10
  • 最后修改日期:2021-03-09
  • 录用日期:2021-05-07
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