Evaluation of the Performance of CMIP5 and CMIP6 Models in Simulating the Victoria Mode–El Niño Relationship

Abstract

AbstractThe Victoria mode (VM) is the second dominant sea surface temperature mode in the North Pacific, forced by North Pacific Oscillation–like extratropical atmospheric variability. Observational studies have shown that the boreal spring VM is closely connected to the following winter El Niño, with the VM efficiently acting as a precursor signal to El Niño events. This study evaluates the relationship of the spring VM with subsequent winter El Niño in the preindustrial simulations of phases 5 and 6 of the Coupled Model Intercomparison Project (CMIP5 and CMIP6). We found that most CMIP5 and CMIP6 models can simulate the basic characteristics of the VM reasonably well. The current CMIP6 models simulate the VM–El Niño connections more realistically as compared to the earlier CMIP5 models. The analysis further suggests that the improved capability of the CMIP6 models to simulate the VM–El Niño relationship is because the CMIP6 models are better able to capture the VM-related surface air–sea thermodynamic coupling process over the subtropical/tropical Pacific and the seasonal evolution of VM-related anomalous subsurface ocean temperature in the equatorial Pacific.