The Princeton ocean general circulation model (POM) was solved to investigate the interannual variability of Kuroshio volume transport. The model domain is from 30ºS to 65ºN in latitude and from 110ºE to 70ºW in longitude. The horizontal grid size of the model is 0.25ºx0.25º in longitude and latitude respectively. After running the model for 40 years from a motionless state, the model was driven from this initial field using the monthly mean fluxes from January 1st 1958 to December 31st 2001. The surface fluxes of wind stress, short wave, long wave, latent heat and sensitive heat are obtained from the reanalysis data of National Centers for Environmental Prediction/National Centersfor Atmospheric Research (NCEP/NCAR) . The salinity flux is estimated from the precipitation rate and the evaporation rate.
The volume transport of model Kuroshio was compared with the observation along ASUKA-line south of Shikoku and PN-line East China Sea. The model results shows interannual variability similar to the observation. The lag correlation between volume transport of Kuroshio and sea surface height in the north Pacific was calculated. The high correlation area appeared near the date line at 30ºN 4 years preceding the increase of Kuroshio volume transport, and this area migrates westward after that. This migration speed is close to the first baroclinic Rossby wave. These results indicate that there is a precursor of Kuroshio volume transport change, and hence the prediction of volume transport may be possible. The lag correlation with windstress curl was also investigated. It was found that the high correlation area for the sea surface height is concerned with the windstress curl anomaly with a peak at 30ºN,175ºW. The volume transport seems to be governed by the first baroclinic Rossby wave propagating westward along 30Z@N latitude line. The transport was also calculated by use of one dimensional quasi-geostrophic (QG) model. The results can explain the dominant property of Kuroshio volume transport change, and a prediction of volume transport was tried by use of a QG toy-model.1. P012. Western Boundary Currents3. Kuroshio, interannual variability4.5. O6.PC7.No8.No9.None |
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