Study On Spatio-Temporal Variation Of Water Environmental Parameters In Semi-enclosed Bay

The hydrodynamics and mass transport characteristics in estuarine and coastal zones are basis for understanding the interactions between physical processes and marine ecosystem dynamics. The study on residual current structure, the transportation of water body and mass composition within the typical semi-enclosed bay are carried out by numerical simulation. Meanwhile, the spatio-temporal variation of water environmental parameters such as transport time scales are numerically modeled and studied. A marine ecosystem model consisting of lower trophic levels is developed and applied to the water environment system of a typical semi-enclosed bay.The current and the mass transportation are studied based on the three dimensional incompressible viscous fluid dynamics model and the tracing techniques including both Eulerian approach and Lagrangian particle tracing approach are applied. The vertical hybrid-layered sigma coordinate is implemented in the model in order to enhance the numerical resolution in the upper layers of the bay.The structures of residual current caused by different dynamic forces including tide, wind, river run-off etc. in the semi-enclosed bay are studied. The calculated results of the Euler residual current and the Lagrange residual current are compared. Moreover, transport time scales such as residence time and age are introduced into the numerical model, and the patterns showed in their histograms of different areas and in the seasonal variation of horizontal distribution are discussed. We also compare the computed difference of transport time scales between Lagrangian particle trajectory method and Eulerian artificial tracer. Results show mass transport characteristics within the bay and water exchange characteristics between ocean and the semi-enclosed bay, all of which are foundation for the understanding of mass transportation in the water environment system.Based on the three dimensional hydrodynamical model, long-term variations of temperature and salinity are simulated, which is necessary for the prediction of statement variables such as dissolved oxygen and phytoplankton biomass. Good agreement is found between the in-situ data and the numerical calculated results. Further the biological module including the loops of nitrogen and phosphorus is developed and coupled to the three dimensional hydrodynamical model. The biological module is applied to the corresponding sea area in a simple case. It shows that the biological module coupled to the three dimensional hydrodynamic model has the potential to be used for the prediction of dissolved oxygen and organism biomass in marine ecosystem.