自20世纪90年代中后期夏季巴伦支海海冰与秋季中国西南地区干旱的联系加强
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国家重点研发计划项目(2017YFA0603802);国家自然科学基金资助项目(41730964);南方海洋科学与工程广东省实验室(珠海)创新团队建设项目(311021001)


Strengthened relationship between summer Barents Sea ice and autumn Southwest China drought after the mid- and late-1990s
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    摘要:

    研究夏季7—8月巴伦支海海冰和秋季9—11月中国西南地区干旱的年际变化的联系,并探讨了其可能机制。结果表明:1979—1997年夏季巴伦支海海冰和秋季中国西南地区干旱在年际尺度上相关不显著,但到1998—2019年,海冰和干旱指数的相关系数增长至-0.69,置信水平达到99%。当夏季7—8月巴伦支海海冰增多时,有利于秋季9—11月中国西南地区发生干旱;当夏季7—8月巴伦支海海冰减少时,则反之。进一步分析其原因可知:1998—2019年,当夏季巴伦支海海冰异常偏多时,海冰异常可以持续到秋季,导致巴伦支海表面湍流热通量负异常,新地岛以西地区的大气变得更加稳定,激发了异常下沉运动。通过异常经向环流作用,进一步促进地中海附近出现上升运动。由此产生的地中海北部对流层高层300 hPa异常辐散风激发了罗斯贝波,波列沿着55°N向东传播,在贝加尔湖地区向南传播至中国北部和西南地区,导致中国西南和华东地区上空出现异常高压,这有利于中国西南地区降水减少、温度升高,进而导致干旱发生。此外,相比于1979—1997年,1998—2019年夏季巴伦支海海冰更大的年际变率可能是导致二者联系加强的一个重要原因。

    Abstract:

    This paper studies the relationship between summer sea ice concentration in the Barents Sea from July to August and autumn drought in Southwest China from September to November, and discusses the possible mechanisms.It is found that the correlation coefficient of interannual variation of autumn drought index in Southwest China and summer sea ice concentration in the Barents sea increases significantly to -0.69 (significant at 99% confidence level) during 1998—2019, whereas they are not well correlated during 1979—1997.When summer sea ice concentration in the Barents Sea increases, it is beneficial for autumn drought occurrence in Southwest China, and vice versa.Further results illustrate that, when there is positive summer sea ice concentration anomalies in the Barents Sea during 1998—2019, the anomalies can persist into autumn, leading to negative surface turbulent heat flux anomalies over the Barents Sea.Thus, the atmosphere in the area west of Novaya Zemlya becomes more stable, triggering anomalous descending motion there.It further induces anomalous ascending motion around the Mediterranean via the anomalous meridional circulation.The resultant anomalous divergent wind in the upper troposphere (300 hPa) of the northern Mediterranean triggers a Rossby wave.The wave train propagates eastwards along 55°N and then begins to spread southwards around the Baikal Lake to North and Southwest China, resulting in an anomalous high over Southwest China to East China.The anomalous high is conducive to the reduced precipitation and higher temperature over Southwest China, resulting in drought there.Additionally, compared with that in 1979—1997, the larger interannual variability of summer sea ice concentration in the Barents Sea during 1998—2019 may be an important reason for the strengthened relationship.

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宦杜斌,范可,徐志清.2022.自20世纪90年代中后期夏季巴伦支海海冰与秋季中国西南地区干旱的联系加强【J】大气科学学报.45.2:167.178

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  • 收稿日期:2021-11-13
  • 最后修改日期:2022-01-15
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  • 在线发布日期: 2022-05-05
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