Temporal Characteristics of Pacific Decadal Oscillation (PDO) and ENSO and Their Relationship Analyzed with Method of Empirical Mode Decomposition (EMD)

Pacific Decadal Oscillation (PDO) is a long-term ENSO-like variability of the North Pacific. It is the first principal component of EOF of the North Pacific SST. ENSO is the strongest signal of annular change of global climate system. Empirical Mode Decomposition (EMD) method is applied to two types of indices.One type of index is the Pacific Decadal Oscillation (PDO) index that represents a long-term ENSO-like variability of the North Pacific. The other type of indices such as Southern Oscillation (SO) index, Nino1+2 SST, Nino3 SST, Nino4 SST and Nino3.4 SST represents ENSO. The relationship between two types of indices shows the temporal characteristics and relationships between the two phenomena. It is found that,for PDO, the good correlations with ENSO only exist on the quasi-2-7-yr timescales and decadal and multidecadal timescales, suggesting that a close relationship between PDO and ENSO only exists among some special intrinsic mode functions at lower frequency band.