Relationship between Pacific Decadal Oscillation and the Extratropical Atmospheric Variation in CMIP5

Abstract:

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. We analyzed the spatial pattern of the PDO from the dataset of the historical runs of the 26 CGCMs of the Coupled Model Intercomparison Project Phase 5 (CMIP5). Our result shows that the inter-model diversity in the PDO pattern is 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). It is particularly interesting 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 SST feedback to the atmospheric circulation in mid-latitudes. This is supported by showing that these models have 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 can play an important role in developing SSTAs.