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尹秋超, 王璐, 葛子安, 等. 2024. 中国夏季极端高温日数年际变化的主要模态及产生机理[J]. 大气科学, 48(X): 1−17. DOI: 10.3878/j.issn.1006-9895.2305.22245
引用本文: 尹秋超, 王璐, 葛子安, 等. 2024. 中国夏季极端高温日数年际变化的主要模态及产生机理[J]. 大气科学, 48(X): 1−17. DOI: 10.3878/j.issn.1006-9895.2305.22245
YIN Qiuchao, WANG Lu, GE Zian, et al. 2024. Dominant Modes of Interannual Variation in Extremely-High-Temperature Days in Summer in China and Associated Mechanisms [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 48(X): 1−17. DOI: 10.3878/j.issn.1006-9895.2305.22245
Citation: YIN Qiuchao, WANG Lu, GE Zian, et al. 2024. Dominant Modes of Interannual Variation in Extremely-High-Temperature Days in Summer in China and Associated Mechanisms [J]. Chinese Journal of Atmospheric Sciences (in Chinese), 48(X): 1−17. DOI: 10.3878/j.issn.1006-9895.2305.22245

中国夏季极端高温日数年际变化的主要模态及产生机理

Dominant Modes of Interannual Variation in Extremely-High-Temperature Days in Summer in China and Associated Mechanisms

  • 摘要: 本文基于1961~2017年中国逐日最高温度资料(CN05.1),通过经验正交函数分解(EOF)揭示了中国夏季极端高温日数(EHTD)年际变化的主导模态,探究了导致各模态形成的关键影响因子和相关物理机制。结果表明:(1)第一模态表现为横贯中国的纬向型分布,该模态主要与北极涛动(AO)有关。AO正位相时从北欧向南传播的罗斯贝波列加强横贯中国的纬向高压异常。(2)第二模态表现为经向偶极子型分布,该模态主要受从北大西洋向东亚地区传播的极地—欧亚型遥相关波列(POL)和赤道西太暖池区上升支加强局地哈德来环流的共同影响,使得华南地区(中国北方)受高压(低压)的控制。前两个模态的极端高温日数增加均与局地高压异常造成的降水减少引起的入射太阳短波辐射增加有关。(3)第三模态的分布集中在青藏高原,主要受从地中海向下游传播的纬向波列的影响。与该波列对应的环流异常一方面会造成水汽辐散、上升运动减弱,从而使得云量减少、向下的云—短波辐射增加,另一方面会造成大气增温、从而使得晴空向下的长波辐射增加,二者共同为极端高温日数增加提供有利条件。本研究结果将有助于加深对中国夏季极端高温变化特征的认识,并为未来开展极端高温的季节预测提供理论参考。

     

    Abstract: This study utilizes daily maximum temperature data (CN05.1) in China from 1961 to 2017 to reveal the dominant modes of interannual variation in the number of summer extremely-high-temperature days (EHTD) through empirical orthogonal function analysis. It further explores the key factors and underlying physical mechanisms leading to each identified mode. The results show that: (1) The first mode is characterized by a zonal distribution across China and is closely associated with the Arctic Oscillation (AO). A Rossby wave train originating from northern Europe and moving southward increases the zonal high anomaly across China when the AO exhibits a positive phase. (2) The second mode shows a meridional dipole pattern, mainly influenced by the Polar–Eurasian teleconnection wave train spreading from the North Atlantic Ocean to East Asia. Further, sea surface temperature anomalies in the western tropical Pacific enhance the local Hadley cell, placing southern China under high-pressure systems and northern China under low-pressure systems. The increase in EHTDs observed in the first two modes is attributed to increased incident solar radiation caused by reduced precipitation owing to local high-pressure anomalies. (3) The distribution of the third mode is concentrated in the Tibetan Plateau, which is mainly influenced by a zonal wave train propagating downstream from the Mediterranean Sea. The circulation anomalies corresponding to the wave train cause the divergence of water vapor and weakening of upward motion, decreasing cloud cover and increasing downward cloudy-sky shortwave radiation. Simultaneously, it causes atmospheric warming, increasing downward clear-sky longwave radiation. Both effects create favorable conditions for an increase in the number of EHTDs. The results of this study deepen the understanding of the characteristics of extremely high temperatures during summer in China, offering a theoretical reference for the seasonal prediction of EHTDs in the future.

     

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