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Ocean Dynamics

, Volume 65, Issue 4, pp 523–538 | Cite as

Analysis of the northern South China Sea counter-wind current in winter using a data assimilation model

  • Jiping XieEmail author
  • Jiang Zhu
  • Laurent Bertino
  • Francois Counillon
Article
Part of the following topical collections:
  1. Topical Collection on Coastal Ocean Forecasting Science supported by the GODAE OceanView Coastal Oceans and Shelf Seas Task Team (COSS-TT)

Abstract

The South China Sea Warm Current (SCSWC) has drawn considerable attentions in the past decade due to its characteristic of flowing against the wind direction along the coast of Southeast China during winter. Observational monitoring of the SCSWC is yet insufficient to firmly assess of the property of this current. Prior modeling attempts have been carried out in idealized or simplified framework, e.g., coarse resolution, unrealistic wind forcing, artificial bathymetry, and/or missing dynamical processes. It is still unclear to what extent the above approximations may affect the properties of the SCSWC. In this study, a state-of-the-art data assimilation system of the South China Sea has been integrated from 1993 to 2005. The system uses the Hybrid Ocean Model (HYCOM) with tidal forcing and is forced with realistic atmospheric forcing. In order to ensure a more realistic positioning of the mesoscale features, the system assimilates along-track altimetry data with the Ensemble Optimal Interpolation (EnOI) to investigate the properties of the SCSWC for the period 1996–2005. The properties of the SCSWC in winter time are investigated and found: the current mainly follows the 100 m isobaths and exists from immediately below the surface to the depth of 50 m with a baroclinic structure; the main core is located at 20–30 m depths and is composed of water warmer than the shelf water; and the width of the current is less than 100 km. Meanwhile, based on the daily output, it was shown that the current is highly transient in January. Additional simulations without tidal forcing and without assimilation suggest that the transient property of the current is mainly driven by the atmospheric forcing while the mesoscale eddies enhance its variability. On the contrary, tidal forcing seems to reduce the strength of the SCSWC, as expected from tidal rectifying of the current.

Keywords

South China Sea counter-wind current Hybrid Coordinate Ocean Model Tidal forcing Ensemble Optimal Interpolation Eddy kinetic energy 

Notes

Acknowledgments

The authors are grateful to two anonymous reviewers for their insightful comments that were helpful in improving the paper. This study was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA01020304), the National Science Foundation of China (Grant No. 41276027), and a grant of CPU time from the Norwegian Supercomputing Project (NOTUR II grant number nn2993k).

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Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  • Jiping Xie
    • 1
    • 2
    Email author
  • Jiang Zhu
    • 2
  • Laurent Bertino
    • 1
  • Francois Counillon
    • 1
  1. 1.Nansen Environmental and Remote Sensing CenterBergenNorway
  2. 2.Institute of Atmospheric PhysicsChinese Academy of SciencesBeijingChina

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