Simulation of SST variability in the North Pacific Ocean and ENSO by an interactive ensemble coupled model

An interactive ensemble (IE) platform is established based on one standard coupled (SC) climate model by the Center for Earth System Science, Tsinghua University. This platform enables the couple of the ensemble of multiple atmospheric models or multiple realizations of one atmospheric model with other model components including the ocean model, land model and the sea ice model. In this study, seven realizations of the atmospheric model with different initial states are coupled with other model components. The integrations of 100 years are used to analyze the simulation of the SST variance in the North Pacific Ocean and ENSO, which are compared to the results from SC. The results show that the IE procedure reduces the variance of SST by more than 85% in the middle and high latitudes of the North Pacific, indicating that much of the SST variability is driven by the atmospheric noise. Moreover, the influence from the atmosphere is mainly through the turbulent heat flux over the ocean surface. The low-frequency period of about 8 years for the SST over Kuroshio extension and central subtropical gyre region in the North Pacific Ocean is mainly forced by the internal atmospheric dynamics. The IE model has more reasonable simulation about the relationship between ENSO and SST in the central North Pacific subtropical gyre region, and the connection between ENSO and middle-high latitude SST in the North Pacific Ocean, while the SC model could not reproduce these phenomena. This implies that strong atmospheric noise will mask out the relationship between ENSO and extratropical SST in the Pacific Ocean. The IE coupled model can reproduce the Pacific-North America (PNA) teleconnection pattern associated with ENSO and its impact on the SST through the turbulent heat flux, which is the main factor for the reproduction of the relationship between ENSO and middle-high latitude SST in the North Pacific. The above analysis validates the reasonable simulation of the proposed IE model. The IE model is proved to have potential application in the study of the air-sea interaction.