摘要:利用1979～2019年NCEP-DOE再分析资料，分析了亚洲中纬度冬季极端低温事件发生频次与巴伦支—喀拉海异常增暖的联系及可能机制。研究表明：巴伦支—喀拉海异常增暖通常对应西伯利亚高压异常增强及亚洲中纬度极端低温频发。进一步分析发现，伴随巴伦支—喀拉海异常增暖，新地岛、乌拉尔山附近出现位势高度正异常，在位势高度正异常的东侧、南侧对应显著的冷平流及下沉运动异常，并在近地面出现异常辐散气流，使得西伯利亚高压增强且向东南延伸。热力学方程诊断的结果表明：西伯利亚高压异常南侧东北风导致的异常冷平流、偏东风异常经过地形造成的异常上升运动以及辐射、感热、潜热交换造成的异常非绝热冷却导致亚洲中纬度近地面温度季节循环振幅增大，有利于极端低温频发。
关键词:巴伦支—喀拉海异常增暖/
极端低温/
西伯利亚高压/
热力学方程诊断
Abstract:Based on the NCEP-DOE reanalysis data during 1979–2019, this paper investigated the relationship and correlation mechanisms between the frequency of winter extremely low temperature events in mid-latitude Asia and the abnormal warming over Barents and Kara Seas. The results show that the abnormal warming over Barents and Kara Seas usually corresponds to the enhancement of Siberian high and the frequent occurrence of extreme low temperatures in mid-latitude Asia. It is found that the positive geopotential height anomaly appears over Novaya Zemlya and Urals with the abnormal warming over the Barents and Kara Seas. Significant cold advection and sinking motion anomalies appear on the east and south sides of the positive geopotential height anomaly and the abnormal divergent flow appears near the ground, which makes Siberian high strengthening and extending to Southeast. The diagnosis using thermodynamic equations further indicates that cold advection anomaly caused by the northeast wind on the south side of the Siberian high pressure anomaly, the ascending motion anomaly caused by the easterly wind anomalies passing through the terrain, and the abnormal diabatic cooling caused by radiation, sensible heat, and latent heat result in an increase in the amplitude of the near-surface temperature’s seasonal cycle in mid-latitude Asia, which in turn favors the frequent occurrence of extreme low temperatures.
Key words:Warming over the Barents and Kara Seas/
Extremely low temperature/
Siberian high/
Diagnosis with thermodynamic equations
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