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General Session 1: Physical oceanic processes: Dynamics and physical-biological-biogeochemical interactions |
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On the residual velocity in sigma coordinates
Tuesday 10th @ 1115-1130
Multi-function Hall
Peng Cheng* , Xiamen University
Presenter Email: pcheng@xmu.edu.cn
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| In shallow coastal regions where water surface fluctuations are not negligible compared to the mean water depth, using the sigma coordinate allows the calculation of residual velocity around the mean water surface level where the water mass is not continuous during the low water period. This study explores the essential characteristics of the residual velocity in sigma velocity through theoretical analysis and numerical experiments. The residual velocity at a sigma layer is the sum of Eulerian velocity and a part of Stokes velocity if the water elevation fluctuation is much smaller than the water depth, and, therefore, is referred to as a semi-Lagrangian velocity that is smaller than Lagrangian velocity. The residual transport velocity is closer to the Lagrangian velocity compared to the semi-Lagrangian velocity, and is equal to the Lagrangian velocity if the velocity is vertically linearly distributed. A numerical simulation of tidal waves in a semi-enclosed basin confirmed the theoretical analysis and showed that the residual velocity in sigma coordinates is reasonable approximation of the Eulerian velocity. |
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