春季北大西洋涛动与东亚夏季风年际关系的转变及其可能成因分析  

Change of the relationship between spring NAO and East Asian summer monsoon and its possible mechanism

作　　者：左金清[1,2] 李维京[1] 任宏利[1] 陈丽娟[1] 

机构地区：[1]中国气象局气候研究开放实验室,北京100081 [2]半干旱气候变化教育部重点实验室/兰州大学,兰州730000

出　　处：《地球物理学报》2012年第2期384-395,共12页Chinese Journal of Geophysics

基　　金：国家科技支撑项目(2007BAC29B04;2009BAC51B05);公益性行业(气象)科研专项(GYHY200806009;GYHY200806005;GYHY200906021);国家自然科学基金项目(40805028;41005038);973计划(2010CB950404)共同资助

摘　　要：本文的相关分析表明,在1948～2009年期间东亚夏季风(EASM)与前期春季(4～5月)北大西洋涛动(NAO)之间存在显著的年际相关关系,但这种关系具有明显的年代际变化特征,即在1970s发生了由正相关到负相关的转变.进一步的合成分析指出,春季NAO与EASM之间年际相关关系的转变,与春季和前期冬季(12～3月)北大西洋海盆尺度的海-气耦合模,即NAO-海温异常(SSTA)三极子耦合模的影响作用密切相关.春季NAO异常对EASM年际变化的影响主要依赖于前者所激发的SSTA三极子模态由春季到夏季的记忆性.然而,该模态不但受到春季NAO的控制,而且还会受到前冬NAO-SSTA三极子耦合模的增强或削弱作用,其中后者的影响作用具有明显的年代际变化特征.在1970s之前,前冬NAO-SSTA三极子耦合模对春季SSTA三极子模态存在明显的非对称作用,即前者主要对后者的正位相异常存在显著的削弱作用;在1970s之后,前者对后者正/负位相异常的影响作用均不明显.因此,在春季NAO对称作用与前冬NAO-SSTA三极子耦合模非对称作用的共同影响下,春季NAO与SSTA三极子模态的年际相关关系存在显著年代际变化,进而引起了春季NAO与EASM的年际相关关系在1970s的转变.The relationship between East Asian Summer Monsoon （EASM） and North Atlantic Oscillation （NAO） was examined by using correlation analysis for the period from 1948 to 2009. It was showed that the EASM was well correlated with the previous spring （April-May） NAO on annual timescale. But their relationship was characterized by large decadal variations, with change of sign from positive to negative in the 1970s. Composite analysis revealed that this change was closely related to the spring and pre-winter （December-March） ocean-scale atmosphere-ocean coupling mode, i.e. the NAO-SSTA （sea surface temperature anomaly） tripolepattern, over the North Atlantic Ocean. The effect of spring NAO on the annual variability of EASM depends on the persistence of SSTA tripole pattern induced by the spring NAO itself. However, this pattern was not only controlled by the spring NAO, but also influenced by the pre-winter NAO-SSTA tripole coupling mode, the effect of which was decadal unstationary. Before the 1970s, the effect of pre-winter NAO-SSTA tripole coupling mode on the spring NAO is asymmetric, i.e. the former only has a significant weakening effect on the positive phase of the latter. After the 1970s, the effect of the former on both the positive and negative phases of the latter was negligible. Therefore, the symmetric effect of spring NAO combined with the asymmetric effect of pre-winter NAO-SSTA tripole coupling mode caused the decadal unstationary relationship between the spring NAO and SSTA tripole pattern, resulting in change of the NAO-EASM relationship in the 1970s.

关 键 词：东亚夏季风 北大西洋涛动(NAO) 海温异常(SSTA) 三极子模态 

分 类 号：P732[天文地球—海洋科学]