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前冬北大西洋涛动与1月欧洲降水联系的年代际增强

Strengthened Linkage between November/December North Atlantic Oscillation and Subsequent January European Precipitation after the Late 1980s

[2021-03-03]


  【中文介绍】

   

  北大西洋涛动(North Atlantic Oscillation, NAO)模态变率与欧洲气候联系密切,是气候预测的有效因子;但是由于NAO本身具有年际与年代际变化特征,其与气候变化的联系并不稳定。


  基于多套再分析及观测资料,本研究主要研究了冬季NAO与欧洲降水联系的年代际变化。19世纪80年代后期以后,前冬北大西洋涛动与1月欧洲降水的联系变得显著:前冬NAO正位相对应北大西洋-欧洲地区1月“偶极型”降水异常,即冰岛以南降水偏多、亚速尔以东降水偏少。这种年代际转变是由北大西洋涛动的内部变率变化造成的:19世纪80年代后期以后,北大西洋上空加剧的风暴轴活动引起北大西洋海温异常,这种异常一直向下延伸到温跃层中部;海温异常持续到次年1月影响局地大气环流,进而形成降水分布异常。此外,地球系统模式大型集合试验数据也证实了气候内部变率对前冬北大西洋涛动与1月降水在80年代后期以后联系增强的影响。

 

  【英文介绍】

   

   This work investigates the non-synchronous relationship between the North Atlantic Oscillation (NAO) and winter European precipitation. The results indicate that the linkage between early-winter (November and December) NAO and the following January precipitation and atmospheric circulation over the Atlantic-Europe sectors became statistically significant after the late-1980s. Before the late-1980s, January precipitation and atmospheric circulation are weakly correlated with early-winter NAO. After the late-1980s, by contrast, the positive phase of the early-winter NAO is generally followed by an anomalous meridional dipole pattern with barotropic structure over the North Atlantic, which provides conditions for more (less) precipitation south of Iceland (east of Azores). Further analysis elucidates that this regime shift may be partly attributed to the change of early-winter NAO which is concurrent with significant change in the intensity of the synoptic and low-frequency eddy interaction over the Atlantic-Europe sectors. Anomalous positive sea level pressure and geopotential height, along with zonal wind anomalies associated with a positive early-winter NAO over the North Atlantic are more significant and extend more northeastward after the late-1980s, which may be induced by an intensified transient eddy feedback after the late-1980s, as well as the enhanced storm track activity over the North Atlantic. Thus, early-winter NAO can induce significant ocean temperature anomalies in the North Atlantic after the late-1980s, which extend downward into the middle parts of the thermocline and persist until the following January to trigger NAO-like atmospheric circulation pattern. Analyses from the Community Earth System Model large ensemble simulations indicate the effects of internal climate variability on such a strengthened linkage.


  【关键图表



图1. 1960/61-1986/87年(左列)和1987/88-2013/14年(右列)两个时段基于前冬NAO指数回归的1月降水异常分布。

                                

  引用格式       

              

  Liu, Y., and He, S. 2020. Strengthened Linkage between November/December North Atlantic Oscillation and Subsequent January European Precipitation after the Late 1980s, Journal of Climate, 33(19), 8281-8300.












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