Influence of the Northern Hemisphere annular mode on ENSO

利用41年再分析资料和大气环流模式（AGCM）研究了北半球环状模态（NAM）对厄尔尼诺/南方涛动（ENSO）的影响。春季NAM指数与次年冬季Nino-3指数之间存在显著的滞后相关性。对流层低层西风带与热带太平洋西部的西风爆发（WWB）的调制有关，在春季通常与不正运动的正相一致，并在夏季和秋季向东延伸。随后，热带太平洋东部初冬出现反映厄尔尼诺现象的暖海温异常。在AGCM实验中，海温固定为气候-月平均分布，WWB的年际调节与春季的不结盟运动变率显著相关，支持春季不结盟运动对次年冬季ENSO爆发的可能影响。

The influence of the Northern Hemisphere annular mode(NAM) on the El Nino/Southern Oscillation(ENSO) was examined using 41-year reanalysis data and an atmospheric general circulation model(AGCM). Significant lag correlations between the NAM index for spring and the Nino-3 index for the following winter were revealed. An anomalous lower tropospheric westerly associated with modulation of the westerly wind burst(WWB) over the western tropical Pacific in spring often coincided with the positive phase of the NAM and extended eastward during summer and autumn. Then, warm sea surface temperature(SST) anomalies reflecting El Nino appeared over the eastern tropical Pacific in early winter. In an AGCM experiment in which SSTs were fixed as a climatological-mean monthly distribution, the interannual modulation of WWB was significantly associated with NAM variability in spring, supporting the possible influence of the NAM in spring on an ENSO outbreak the following winter.