热带季节内振荡与北大西洋涛动年际变化的关系

摘要

Using K-means clustering algorithms, four weather regimes over the North Atlantic–European region are obtained. Moreover, the relationship between the Madden–Julian Oscillation (MJO) in the tropics and the four weather regimes over the North Atlantic–European region is investigated. It is found that the winter mean North Atlantic Oscillation (NAO) index can be characterized by the number of days of NAO events calculated by K-means clustering algorithms. During two periods, 1978–1990 (P1) and 1991–2010 (P2), phase 3 (6) of the MJO leads to a positive (negative) NAO regime. In particular, the MJO is found to be very important for the NAO transition during P1, but unimportant during P2. When the MJO is within the first (sixth) phase during P1, the NAO event can transit from the weak negative (positive) phase to the positive (negative) phase. However, only the transition between dipole and wave train patterns is evident during P2, when the MJO is in the first phase.%　　运用K均值聚类法将冬季北大西洋及欧洲地区的天气流型分为4种不同的流型。研究了不同阶段8种不同位相的热带季节内振荡（MJO）与这4种流型的年际变化的关系。通过一系列的对比试验发现，K均值聚类法划分得到的不同位相的北大西洋涛动（NAO）的天数能很好地反映NAO指数；无论是在1978～1990年（简称为P1阶段）还是在1991～2010年（简称为P2阶段），MJO第3（6）位相影响NAO正（负）位相；但在P1阶段存在NAO的位相转换，当MJO处于第1位相时，NAO由弱的负位相转换为正位相，当MJO处于第6位相时， NAO由正位相转换为负位相；而在P2阶段NAO并没有明显的位相转换，当MJO处于第1位相时，NAO由偶极子结构转换为波列结构。