太阳活动变化对东亚冬季气候的非对称影响及可能机制

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

基于1959～2013年的观测和再分析资料以及10.7 cm （2800MHz）太阳射电通量资料,本文分析了太阳活动变化与东亚冬季气候的相关关系,分析结果表明：太阳活动变化与东亚冬季大气环流有较好的相关性,且在太阳活动的强、弱时期该相关关系存在很大差异,在强太阳活动时期太阳活动变化与东亚冬季气候的联系更为显著,而在弱太阳活动时期二者之间的直接联系微弱,这表明太阳活动变化对东亚冬季气候的影响具有非对称性特征.在太阳活动较强的时期,随着太阳活动的增强,东亚中高纬对流层中层的大气环流倾向纬向型,东亚大槽减弱,850 hPa出现异常偏南风,地面上西伯利亚高压以及冬季风减弱,东亚大部分地区气温显著偏高;而在太阳活动较弱的时期,太阳活动的年际差异与东亚冬季大气环流之间几乎不存在显著联系.分析太阳活动较强和较弱时期纬向平均纬向风的差异发现,其间平流层行星波活动、热带西北太平洋海表温度的差异可能是造成这种非对称影响的重要原因.在强太阳活动时期,平流层行星波在太阳活动的异常增强年有异常的从极地向赤道的水平传播,高纬地区E-P通量（Eliassen-Palm flux）异常辐散,导致中高纬西风及北极涛动（AO）增强,同时热带西北太平洋海温异常偏冷,海陆热力差异缩小,大气环流经向度减弱,东亚冬季风偏弱.

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.