Process study on decadal variations of the North Pacific oceanic fronts using initialized hindcast data

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By analyzing initialized hindcast data together with the observations, we have clarified the physical processes controlling decadal variations around the oceanic fronts of the North Pacific, where the signals of the Pacific Decadal Oscillation are observed strongest. Over the subtropical front, realistic representation of the front structure and the heat transport by the ocean gyre circulation contributes to our high skill in predicting the decadal changes of the ocean temperature. Over the subarctic front, on the other hand, our error sensitivity analyses have revealed that the delayed response of the ocean to the Aleutian Low fluctuations controls the quality of our decadal hindcasts primarily through the oceanic Rossby wave adjustment. For the climate modelling and the initialization, particularly toward reducing prediction uncertainty over the subarctic front, we should further focus on these processes in the extratropical atmosphere and the tropical atmosphere-ocean coupling.