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东亚冬季气温异常冷暖反转模态的非对称特征及其维持机制

Asymmetric Characteristics and Maintenance Mechanisms of the East Asian Winter Temperature Anomaly Reversal Mode

  • 摘要: 东亚地区气温异常的冷暖反转是全球变暖背景下冬季最重要的气候现象之一。和冬季平均气温异常相比,冷暖反转现象的气候预测不确定性更大,其造成的不利影响也更为重大。本文基于1980/81−2022/23年冬季大气再分析资料,利用季节经验正交分解和合成分析方法,分析了东亚冬季气温冷暖反转模态的年际变化特征。结果表明,虽然东亚冬季气温冷暖反转模态的不同过程都与西伯利亚高压、欧亚大气遥相关和北极极涡异常的季节内相互作用有关,但“暖转冷”过程的年际变率明显强于“冷转暖”过程,说明冷暖反转模态的年际变化存在明显的非对称性。在“暖转冷”过程中,前冬类似东大西洋/西俄罗斯型的大气遥相关正位相在后冬转为负位相,西伯利亚高压随之逐渐增强,后冬东亚地区冷空气更为活跃。而在“冷转暖”过程中,冬季北极极涡强度由弱变强,西伯利亚高压随之由强变弱,有利于东亚地区出现前冬冷、后冬暖的温度异常特征。进一步分析表明,冬季La Niña背景下的北大西洋和热带印度洋海温异常是“暖转冷”过程的可能影响因子,而秋末巴伦支-喀拉海海冰异常偏少则是“冷转暖”过程的潜在前兆信号,说明大气下垫面外强迫差异是造成东亚冬季冷暖反转模态不同过程强度不对称的重要原因。因此,东亚冬季冷暖反转现象的气候预测需要考虑不同大气下垫面外强迫影响的多样性。

     

    Abstract: The reversal of temperature anomalies from warm to cold and vice versa in the East Asian region is a significant climatic phenomenon occurring during the winter season under the context of global warming. Compared to the variability of seasonal-mean winter temperature anomalies, the climate prediction uncertainty for the reversal phenomenon is greater, and its adverse effects are more significant. In this study, seasonal empirical orthogonal decomposition and composite analysis were performed on atmospheric reanalysis data from the winters of 1980/81 to 2022/23 to investigate the interannual variability of the East Asian winter temperature anomaly reversal mode (TARM). The results indicate that although the different processes of the East Asian winter TARM are related to intraseasonal reversals of the Siberian High, the Eurasian teleconnection, and the Arctic vortex anomalies, the interannual variability of the “warm-to-cold” mode is significantly stronger than that of the “cold-to-warm” mode, suggesting a pronounced asymmetry in the interannual variability of TARM. In the “warm-to-cold” mode, the lower-level Siberian High strengthens over time: the positive phase of the East Atlantic–West Russia–like teleconnection in early winter shifts to a negative phase in late winter, leading to more active cold air. Conversely, in the “cold-to-warm” mode, the intensity of the winter Arctic vortex shifts from weak to strong, and subsequently, the Siberian High weakens, favoring the appearance of temperature anomalies that are cold in early winter and warm in late winter. Further analysis shows that the North Atlantic and tropical Indian Ocean sea surface temperature anomalies with La Niña are important factors influencing the “warm-to-cold” mode, while a reduction in the Barents–Kara sea ice in November acts as a precursor signal for the “cold-to-warm” mode. Therefore, the diversity of underlying atmospheric conditions is an important cause of the asymmetry of the East Asian winter TARM. Therefore, climate prediction for the East Asian winter TARM should consider the diversity of the underlying atmospheric conditions.

     

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