Pacific Decadal Oscillation and its relation to the extratropical atmospheric variation in CMIP5

It is investigated how the simulated Pacific Decadal Oscillation (PDO) differs among various coupled general circulation models (CGCMs), and how it is related to the simulated atmospheric variation in the North Pacific. The dataset of the historical runs of the 26 CGCMs reported to the Coupled Model Intercomparison Project Phase 5 are used. It is shown that the differences in the PDO pattern among 26 CGCMs are closely related to diverse displacements of the simulated Aleutian Low (AL), that is, the PDO pattern is highly dependent on longitudinal and latitudinal position of the anomalous AL associated with the PDO (PDO-related AL; AL(PDO)). In addition, it is demonstrated that in the models that have the southward shift of the AL(PDO), the North Pacific sea surface temperature anomalies (SSTAs) associated with the PDO tend to modulate the atmospheric circulation strongly, implying strong two-way feedback between ocean and atmosphere. Therefore, this gives relatively strong persistency of the PDO. It is also found that the PDO in these models is highly correlated with the variation of the Kuroshio Extension current, implying that ocean dynamical processes play an important role in developing SSTAs.