ISSN 1006-9895

CN 11-1768/O4

Asymmetric Impact of Solar Activity on the East Asian Winter Climate and Its Possible Mechanism
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    Abstract:

    The relationship between solar activity and the East Asian Winter Climate (EAWC) was investigated using observation and reanalysis data and solar 10.7 cm radio flux data from 1959 to 2013. The results show that solar activity correlates well with the winter atmospheric circulation over East Asia (EA). However, interestingly, this relationship exhibits large differences between strong and weak solar activity periods, suggesting an asymmetric solar influence on the EAWC. Further investigation indicates that the linkage between solar activity and the EAWC is robust during active solar periods, while during inactive phases, the connection is fairly weak in comparison. During the active solar period, with strengthening of solar activity, the geopotential height in the mid-troposphere increases significantly over the mid-latitudes of the EA, resulting in a weakened East Asian Trough (EAT). Meanwhile, southerly anomalies exist at 850 hPa over EA, and the Siberian high is weakened in addition to the East Asian Winter Monsoon (EAWM) at the surface, giving rise to significantly positive temperature anomalies in most parts of the EA. Nevertheless, during inactive solar periods, there is almost no obvious link between the interannual variability of solar activity and the East Asian winter atmospheric circulation. Comparison of the strong solar period with the weak period shows that the abnormal planetary wave activity and Sea Surface Temperature (SST) anomalies over the northwestern Pacific could be crucial for such an asymmetric solar influence. During the active solar period, when solar activity becomes stronger, planetary waves in the stratosphere propagate toward the equator abnormally, resulting in the divergence of the Eliassen-Palm flux in high-latitude areas and enhancement of the Arctic Oscillation and high-latitude westerlies. Meanwhile, the SST in the tropical northwestern Pacific decreases with the increase in solar activity, which reduces the thermal contrast between the Eurasian continent and the Pacific, and weakens the meridional flow patterns, resulting in an inactive EAWM.

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History
  • Received:June 17,2014
  • Revised:October 20,2014
  • Adopted:
  • Online: July 08,2015
  • Published: