Dynamical Statistic Analysis of Decadal Anomalies of Air-Sea Circulation in the North Pacific during Winter

In this paper, the Complex Empirical Orthogonal Function (CEOF) and wavelet analysis methods are employed to study the decadal variations of the first and second modes of atmospheric and oceanic circulation in the North Pacific during winter. The relationships between them and the Pacific Decadal Oscillation (PDO) and North Pacific Gyre Oscillation (NPGO) mode are also discussed. The correlations between the time coefficients of the first two modes and the PDO and NPGO index are reasonably high, and the wavelet analysis of the time coefficients show obvious decadal periods of about 22 and 12 years, respectively, which are the same as the decadal variations of the PDO and NPGO mode. The regression coefficient field of the first two time coefficients with the SST Anomalies (SSTAs) is quite similar to the spatial distribution of the PDO and NPGO mode. The spatial distributions of the first two modes of atmospheric circulation anomalies resemble those of the Aleutian low (AL) mode and North Pacific Oscillation (NPO) mode, which can be defined as the wind field mode of the AL mode and NPO mode, while the first two modes of oceanic flow anomalies are defined as the flow field mode of the PDO and NPGO mode for the same reason. In addition, the distributions of vertical velocity calculated from the near-surface circulation anomalies of the two modes are similar to that of the PDO and NPGO mode, which demonstrates the importance of dynamical variation caused by vertical motion in the formation of the PDO and NPGO mode, and the oceanic circulation anomalies acts as a medium in this process.