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Physics of estuaries and coastal seas
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The possible effect of stratification on the vertical structure of the semidiurnal tidal ellipse in the Changjiang River estuary, China (Invited)
Monday 7th @ 1010-1030, Conference Hall
John Z. Shi* , School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University
Xiang Pu, School of Naval Architecture, Ocean and Civil Engineering, Shanghai Jiao Tong University,
Guo-Dong Hu, Survey Bureau of Hydrology and Water Resources of the Changjiang River Estuary, Changjiang Water Resources Commission, Shanghai
Presenter Email: zshi@sjtu.edu.cn |
| The possible effect of stratification on the vertical structure of the semidiurnal tidal ellipse in the Changjiang River estuary is analyzed based on obervational data. A pycnocline occurs at each station along the North Passage on a neap tide only. Calculated potential energy anomalies within the North Passage are 100 - 200 Jm-3 larger on a neap tide than on a spring tide. The tidal ellipses degenerate to rectilinear motion at each layer of the water column at each station along the North Passage, while they rotate clockwise at each station over the Hengsha Shoal. The surface-to-bottom inclination angle difference of the tidal ellipse at a seaward station is 40 degree on a neap tide but a few degrees on a spring tide. Rapid changes in the inclination angles and phrase shifts of the tidal ellipses occur at the pycnocline. An abrupt reduction in the vertical eddy viscosity at the pycnocline seems to be the major cause for the vertical variability of ellipticity, inclination angle and phase of the tidal ellipses on a strongly stratified neap tide. The surface-to-bottom ellipticy difference appears to have a positive linear relation with the overall Richardson number mainly along the North Passage on a neap tide. |
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