Joint principal component: wavelet analysis of atmospheric teleconnection: the North Atlantic Oscillation case

The impact of the North Atlantic Oscillation (NAO) on synoptic conditions in Ukraine can not be considered as fully defined as the territory of Ukraine is located at the transitional boundary of processes associated with the NAO. As a rule, common methods based on the principal component analysis (PCA) can not reveal the impact of the NAO. Moreover, the analysis of synopticscale processes based on the data with the one-day (or lesser) discreteness is affected by noise. In this paper, the wavelet analysis is used jointly with the PCA to determine time intervals when a linkage between the NAO and processes over Ukraine was significant. Such an approach allowed revealing the time intervals during the cold seasons, when simultaneous variations of synoptic conditions in North Atlantic and Eastern Europe occurred at quasisynoptic time scales. Usually, that process is observed not very often, but simultaneous variations can be in progress during a few weeks. The coherent changes of synoptic conditions do not depend on the strength and phase of the NAO and can be both in-phase and anti-phase. The significant wavelet coherence is probably registered when two intensive synoptic processes different from general synoptic situation are observed.