Simulation and Projection of the Pacific Decadal Oscillation Based on CMIP5 Coupled Models

Historical simulation outputs from the Coupled Model Intercomparison Program Phase 5 (CMIP5) climate models with a categorization method were used in this study to evaluate the performance of coupled models in simulating the Pacific Decadal Oscillation (PDO). While several of the 40 models under examination failed to reproduce the characteristics of PDO pattern, the majority of the models can reproduce the interdecadal cycle of PDO well. The good performance of the category-1 models in simulating the PDO pattern can be attributed to the relationship of the SSTA (sea surface temperature anomaly) between tropical Pacific and North Pacific being captured by these models. Further, the impact of the decadal SST variation in the tropic Pacific on the SST variation in the North Pacific via atmospheric teleconnection was reproduced using these models. In contrast, the models with poor simulation for the PDO pattern failed to reproduce the tropics-extratropics linkage in the SST anomalies that was induced by atmospheric teleconnection. This result indicates the importance of the decadal SST variation in the Tropic Pacific for the formation of PDO. Under RCP4.5 (Representation Concentration Pathway Scenarios 4.5), it is suggested that the first EOF (empirical orthogonal function) of SST variability over the North Pacific for the 21st century is a uniform positive pattern with a corresponding time series indicating an upward trend. Meanwhile, the second leading pattern of the 21st-century EOF analyses shows the spatial variability of the PDO diploe pattern.