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冬季亚洲两种大气环流型对云南低温事件的影响

The impact of two atmospheric circulation patterns in Asia on low-temperature events in Yunnan province during winter

  • 摘要: 利用1961—2022年云南125个国家气象站冬季逐日平均气温观测资料、NCAR/NCEP大气环流再分析资料,分析了冬季亚洲环流变化的主要类型及其对云南低温事件的影响,发现冬季亚洲500 hPa大气环流存在纬向型和经向型两种环流类型,并对云南低温事件产生明显不同的影响。纬向型环流时,冷空气从贝加尔湖直接南下,主要影响东亚东部,云南低温事件也主要发生在东部地区,此时的低温过程与乌拉尔山高压和西伯利亚高压加强、欧亚中高纬度波列的活动密切联系;而经向型时,冷空气伴随贝加尔湖地区的异常反气旋东侧偏北气流沿着东亚大陆东部沿岸南下,并在中低纬度地区以回流的形式向东南推进,活动位置偏南偏西,使得云南全省、青藏高原和东南亚低纬度地区气温偏低,此时的低温过程主要与副热带波列的活动和青藏高原海平面气压(Surface level Pressure,SLP)的正距平加强有关,与乌拉尔山和西伯利亚地区的高压加强关系不密切。

     

    Abstract: Using the daily average temperature data of 125 national meteorological observation stations and NCAR/NCEP reanalysis data from 1961 to 2022, the main patterns of Asian circulation changes in winter and their impact on low-temperature events in Yunnan province were analyzed. The results show that there are two patterns of atmospheric circulation at 500 hPa in Asia during winter, namely zonal and meridional patterns, and the impact of the two patterns on low-temperature events in Yunnan province is significantly different. During the zonal circulation pattern, the stronger cold air flows directly southward from Lake Baikal to low latitudes, mainly affecting the eastern part of East Asia. The low-temperature events in Yunnan province also mainly occur in the eastern region. At this time, the low-temperature process is closely related to the strengthening of the Ural Mountains High and the Siberian High, as well as the wave trains at mid-to-high latitudes in Eurasia. During the meridional circulation pattern, the cold air flows southward along the eastern coast of the East Asian continent with the northerly airflow of the eastern side of the anomalous anticyclone in Lake Baikal, and moves southeast in the form of backflow in mid-to-low latitude areas. The activity is located southward and westward, which is beneficial for the low temperature of Yunnan province, the Tibet Plateau, and low latitude areas in Southeast Asia. At this time, the low-temperature events are mainly related to the changes in the subtropical wave train and the strengthening of positive surface level pressure (SLP) anomalies on the Tibet Plateau, but not closely related to the strengthening of High pressure in the Ural Mountain and the Siberian.

     

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