Interannual and interdecadal variabilities in the Pacific in an MRI coupled GCM |
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Authors: | S Yukimoto M Endoh Y Kitamura A Kitoh T Motoi A Noda T Tokioka |
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Institution: | (1) Meteorological Research Institute, 1-1 Nagamine, Tsukuba, Ibaraki 305, Japan, JP;(2) Japan Meteorological Agency, Tokyo 100, Japan, JP |
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Abstract: | Interannual and interdecadal variabilities in the Pacific are investigated with a coupled atmosphere-ocean GCM developed
at MRI, Japan. The model is run for 70 years with flux adjustments. The model shows interannual variability in the tropical
Pacific which has several typical characteristics shared with the observed ENSO. A basin-scale feature of the principal SST
variation for the ENSO time scale shows negative correlation in the central North Pacific with the tropical SST, similar to
that of the observed one. Associated variation of the model atmosphere indicates an intensification of the Aleutian Low and
a PNA-like teleconnection pattern as a response to the tropical warm SST anomaly. The ENSO time scale variability in the midlatitude
ocean consists of the westward propagation of the subsurface temperature signal and the temperature variation within the shallow
mixed layer forced by the anomalous atmospheric heat fluxes. For the interdecadal time scale, variation of the SST is simulated
realistically with a geographical pattern similar to that for the ENSO time scale, but it has a larger relative amplitude
in the northern Pacific. For the atmosphere, spatial structure of the variation in the interdecadal time scale is also similar
to that in the ENSO time scale, but has smaller amplitude in the northern Pacific. Long oceanic spin-up time (>∼10 y) in the
mid-high latitude, however, makes oceanic response in the interdecadal time scale larger than that in the ENSO time scale.
The lagged-regression analysis for the ocean temperature variation relative to the wind stress variation indicates that interdecadal
variation of the ocean subsurface at the mid-high latitudes is considered as enhanced ocean gyre spin-up process in response
to the atmospheric circulation change at the mid-high latitudes, remotely forced by the interdecadal variation of the tropical
SST.
Received: 6 November 1995 / Accepted: 19 April 1996 |
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