Vertical structure of tidal currents in the Xuliujing Section of Changjiang River Estuary |
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Authors: | Zhigao Chen Ya Ban Xiaoye Chen Dajun Li Shengping Wang |
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Institution: | 1.Faculty of Geomatics, East China University of Technology, Nanchang 330013, China2.Chongqing Academy of Metrology and Quality Inspection, Chongqing 401120, China3.Nanjing White Shark Surveying and Mapping Technology Co., Ltd, Nanjing 210038, China4.Key Laboratory of Marine Environmental Survey Technology and Application, Ministry of Natural Resources, Guangzhou 510300, China |
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Abstract: | Three long-term fixed acoustic Doppler current profilers were first used for investigating the vertical structure of tidal currents in Xuliujing Section of Changjiang River Estuary. Moreover, three different periods (spring, summer and fall) were also considered for investigating seasonal variations. The semi-diurnal tides were the most energetic, with along-channel speed of up to 80 cm/s for M2 constituent, which dominates at all stations with percent energy up to 65%–75% during seasons. The shape of tidal ellipses of the most energetic semi-diurnal constituent M2 showed obvious polarization of the flow paralleling to the riverbank, with the minor semi-axis being generally less than 20% of the major one. The maximum velocity of mean current is appeared in top layers at all the three stations, and the velocity decreased with the depth. The seasonal variations of direction are also observed, which is probably caused by complex local topography since the erosion and deposition in riverbed. Observed vertical variation of four parameters of M2 ellipses, agreed well with the optimally fit frictional solutions in top and middle layers. However, there was an obvious difference between frictional model and observed data in the lower water column. Discrepancies are probably on account of stratification, which strengthens in summer and fall due to the freshening influence of the Changjiang River Estuary outflow. |
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Keywords: | vertical structure seasonal variations tidal current mean current acoustic Doppler current profiler Changjiang River Estuary |
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