A teleconnection pattern of upper-tropospheric circulation anomalies over the Eurasian continent associated with the interannual variability of atmospheric convection over the tropical western North Pacific in July

Abstract

It has been well documented that the interannual variation of atmospheric convection over the tropical western North pacific (WNP) affects the East Asian climate in summer significantly, and can be influenced by the preceding winter ENSO. However, there is also a large portion of WNP convection variability that cannot be explained by the preceding ENSO. This study suggests that, particularly in July, the WNP convection anomalies are closely associated with a teleconnection pattern of upper-tropospheric circulation anomalies over the Eurasian continent, which is characterized by an anomalous cyclone over Europe, an anticyclone over Central Asia, and a zonally elongated cyclone over East Asia. This teleconnection pattern can also be detected by the first leading mode of upper-tropospheric circulation in July. The authors conclude, based on the present results and those of previous studies, that the teleconnection pattern induces WNP convection anomalies through Rossby wave breaking near the Asian jet exit region, and this impact is comparable to that of the preceding winter ENSO.摘要热带西北太平洋大气对流的年际变化对东亚夏季气候有着显著影响, 而且受到前冬ENSO的影响. 然而, 还有相当多的西北太平洋对流年际变化不能由前冬ENSO解释. 本文表明, 7月西北太平洋对流受到欧亚大陆对流层上层遥相关型的显著影响, 且这一影响与前冬ENSO的影响程度相当. 该遥相关型表现为位于欧洲的气旋式环流异常, 中亚的反气旋式环流异常和东亚带状延伸的气旋式环流异常, 并表现为7月对流层上层环流的第一主模态. 基于本文的结果并结合前人的研究, 作者认为这一遥相关型能通过亚洲急流出口区附近的罗斯贝波破碎引起西北太平洋对流异常.