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欧亚大陆春季融雪量与东亚夏季风的可能联系

Linkage between Spring Eurasian Snowmelt and East Asian Summer Monsoon

  • 摘要: 通过对观测资料的分析, 本文研究了春季欧亚大陆融雪量与东亚夏季风的关系, 并初步讨论了其可能联系机制。研究表明, 春季融雪量EOF (Empirical Orthogonal Function) 第一模态表现出年代际变化特征, 这与东亚夏季风和中国夏季降水的年代际转型具有非常好的一致性。而EOF第二模态与东亚夏季风在年际尺度上具有同位相变化关系, 当春季融雪量在东西伯利亚和巴尔喀什湖附近异常偏多时, 后期在东亚地区容易出现由高纬至低纬的“负—正—负”经向波列结构。融雪量异常偏少时, 情况则相反。文中初步分析了春季融雪量异常与后期夏季东亚地区大气环流出现经向波列结构的可能联系机制, 指出东西伯利亚以及巴尔喀什湖附近异常偏多的春季融雪量能够在该地区促使位势高度场表现为正异常, 随着时间的演变, 巴尔喀什湖附近地区的高压向东移动发展, 东西伯利亚地区的高压一部分向低纬移动, 可能造成夏季东亚地区的经向波列结构, 进而对东亚的天气和气候产生影响。

     

    Abstract: The effects of spring Eurasian snowmelt on the East Asian summer monsoon (EASM) and summer precipitation in China, in addition to a possibly related physical mechanism, were investigated by using observation data. The leading mode of spring Eurasian snowmelt showed decadal variation, which has good agreement with the EASM interdecadal transition and Chinese summer rainfall. In addition, the second mode of the snowmelt variability correlates positively to EASM variability. When the snowmelt in East Siberia near Balkhash Lake increases in the spring, the EASM tends to appear in a negative-positive-negative meridional wave train structure from high to low latitudes in the summer. When snowmelt decreases, opposite conditions appear. The link mechanism of the spring snowmelt and summer atmospheric circulation in East Asia may be attributed to positive feedback between abnormal snow and atom- spheric thickness anomalies in the same regions during the same period, which promotes two high-pressure systems. Subsequently, the Balkhash Lake high-pressure system develops eastward, and part of the East Siberian high pressure system moves to lower latitudes. As a result, atmospheric circulations in East Asia may form the meridional wave train structure in the summer, which may lead to an anomalous change in the East Asian summer weather and climate.

     

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