Diverse influences of spring Arctic Oscillation on the following winter El Nino-Southern Oscillation in CMIP5 models

This study evaluates the ability of 35 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5) historical climate simulations, in reproducing the connection between boreal spring Arctic Oscillation (AO) and its following winter El Nino-Southern Oscillation (ENSO). The spring AO-winter ENSO correlations range from - 0.41 to 0.44 among the 35 models for the period of 1958-2005. Ensemble means of the models with positive and negative AO-ENSO correlations both show strong spring sea surface temperature (SST) cooling in the subtropical North Pacific during a positive phase of spring AO, which is conducive to occurrence of a La Nina event in the following winter. However, the models with positive AO-ENSO relations produce a pronounced spring cyclonic anomaly over the subtropical northwestern Pacific and westerly anomalies over the tropical western Pacific (TWP). These westerly wind anomalies bring SST warming and positive precipitation anomalies in the tropical central-eastern Pacific (TCEP) during the following summer, which would maintain and develop into the following winter that support an El Nino-like pattern in the TCEP via a positive air-sea feedback mechanism. By contrast, the models with negative AO-ENSO connections fail to reproduce the spring AO-related cyclonic anomaly over the subtropical northwestern Pacific and westerly wind anomalies in the TWP. Thus, these models would produce a La Nina-like pattern in the subsequent winter. Difference in the spring AO-associated atmospheric anomalies over the subtropical North Pacific among the CMIP5 models may be attributed to biases of the models in simulating the spring climatological storm track.