Spring Arctic Oscillation-western North Pacific connection in CMIP5 models

Abstract

This study evaluates the simulation of the spring Arctic Oscillation (AO)-western North Pacific linkage based on the 16 state-of-the-art climate models from the Coupled Model Intercomparison Project Phase 5. The validation focuses on the predominant process connecting the spring AO with the East Asian summer monsoon: the formation and persistence of the spring AO-associated cyclonic anomaly over western North Pacific (WPCA) from spring to summer. The results indicate that 8 of 16 models can reproduce both the formation and persistence of the WPCA. Because the formation of the WPCA is directly related to the existence of the spring upper-level North Pacific atmospheric dipole (NPAD), the analyses suggest that a given model can reproduce the spring AO-associated NPAD if the model is capable of simulating the spring AO-associated deceleration of the subtropical westerly jet and the transient eddy activities around the westerly jet exit. Furthermore, the westerly jet anomalies are closely related to the simulated mean state of the westerly jet and the AO Pacific component, which could be further attributed to the simulated sea surface temperature biases over the equatorial Western Pacific.