Tidally induced upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer

  • Lü XinGang 
  • Qiao FangLi 
  • Xia ChangShui 
  • Yuan YeLi 
Article

Abstract

MASNUM wave-tide-circulation coupled numerical model (MASNUM coupled model, hereinafter) is developed based on the Princeton Ocean Model (POM). Both POM and MASNUM coupled model are applied in the numerical simulation of the upwelling off Yangtze River estuary and in Zhejiang coastal waters in summer. The upwelling mechanisms are analyzed from the viewpoint of tide, and a new mechanism is proposed. The study suggests that the tidally inducing mechanism of the upwelling includes two dynamic aspects: the barotropic and the baroclinic process. On the one hand, the residual currents induced by barotropic tides converge near the seabed, and upwelling is generated to maintain mass conservation. The climbing of the residual currents along the sea bottom slope also contributes to the upwelling. On the other hand, tidal mixing plays a very important role in inducing the upwelling in the baroclinic sea circumstances. Strong tidal mixing leads to conspicuous front in the coastal waters. The considerable horizontal density gradient across the front elicits a secondary circulation clinging to the tidal front, and the upwelling branch appears near the frontal zone. Numerical experiments are designed to determine the importance of tide in inducing the upwelling. The results indicate that tide is a key and dominant inducement of the upwelling. Experiments also show that coupling calculation of the four main tidal constituents (M2, S2, K1, and O1), rather than dealing with the single M2 constituent, improves the modeling precision of the barotropic tide-induced upwelling.

Keywords

upwelling dynamic mechanism numerical simulation tidal movement tidal mixing front 

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Copyright information

© Science in China Press 2007

Authors and Affiliations

  • Lü XinGang 
    • 1
    • 2
    • 3
    • 4
  • Qiao FangLi 
    • 1
    • 2
  • Xia ChangShui 
    • 1
    • 2
  • Yuan YeLi 
    • 1
    • 2
  1. 1.The First Institute of OceanographyState Oceanic AdministrationQingdaoChina
  2. 2.Key Laboratory of Marine Science and Numerical Modeling (MASNUM)State Oceanic AdministrationQingdaoChina
  3. 3.Institute of OceanologyChinese Academy of SciencesQingdaoChina
  4. 4.Graduate University of the Chinese Academy of SciencesBeijingChina

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