Journal of Oceanography

, Volume 69, Issue 2, pp 175–190 | Cite as

Simultaneous assimilation of surface drifter data, satellite and in situ observations for improved estimates of meso-scale variability in the Kuroshio Extension Region

Original Article

Abstract

In order to better estimate meso-scale variabilities in the energetic Kuroshio Extension (KE) region, simultaneous assimilation of drifter-derived velocity data, together with satellite and in situ hydrographic data, is attempted by using a high-resolution 4-dimensional variational data assimilation (4D-VAR) system. Our experimental results, both with and without assimilation of drifter data (Exp. Drf and Exp. Ref, respectively) for the period during Aug–Oct 2005, show that the reproduced fields in Exp. Drf better reflect the observed meso-scale features such as the KE meandering jet and associated eddies. The adjoint sensitivity analysis indicates that our 4D-VAR system has the ability to provide a more realistic timeseries of the meandering jet structures that play a key role in the intergyre exchange between the subtropical and subarctic gyres in the North Pacific. In addition, the observed information from the surface drifters works to improve the subsurface structure. These results illustrate the advantage of our 4D-VAR simultaneous assimilation with the addition of drifter-derived surface velocity information.

Keywords

Data assimilation Surface drifter 4D-Var method Kuroshio Extension Mesoscale eddies 

Notes

Acknowledgments

We thank Dr. J.P. Matthews for his critical reading of our manuscript. We are grateful to two anonymous reviewers for their constructive comments. The numerical calculations are carried out on a Fujitsu Prime 590 Power HPC2500 in the Academic Center for Computing and Media Studies, Kyoto University. The present work is partly supported by Grant-in-Aid for JSPS Fellows.

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Copyright information

© The Oceanographic Society of Japan and Springer Japan 2013

Authors and Affiliations

  1. 1.Department of Geophysics, Graduate school of ScienceKyoto UniversityKyotoJapan
  2. 2.Data Research Center for Marine-Earth SciencesJapan Agency for Marine-Earth Science and TechnologyKanagawaJapan

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