Numerical Simulation Of The Circulation And Its Driving Factors In The Bohai Sea

As an important part of coastal waters of China, Bohai Sea is significant to the natural ecological environment and economic development of the region. With the little average depth and the unique semi-enclosed structure, Bohai Sea has peculiar hydrodynamic characteristics. The material and energy transport in the Bohai Sea is mostly dependent on the circulation, therefore the study of the circulation the in the Bohai Sea and the comprehensive analysis of different driving factors of the circulation are very necessary. Based on Lagrangian particle tracing method, this study adopted the numerical simulation method to study the circulation and its driving factors in the Boahi Sea.Firstly, the Environmental Fluid Dynamics Code, based on the orthogonal curvilinear grid, was used to build the3-D baroclinic model of the Bohai Sea, considering the effects of real wind field, heat flux of the sea surface and the river discharge around the Bohai Sea. The hydrodynamic and thermohaline process of the Bohai Sea was simulated with the established model. The results of the numerical simulation, including the co-tidal charts, tidal current ellipse figures and the thermohaline field in the horizontal plane, were similar to those in the Marine Atlas. In addition, the observed tidal elevations, tidal harmonic constants and the process of the temperature and salinity were used to validate the model. The results of the comparison showed that the3-D model played the hydrodynamic characteristics and the thermohaline characteristics well.With the established model, the winter and summer circulation in the Bohai Sea was studied by Lagrangian particle tracing method. The study shows that the transport of particles behaved3-D structure was clear in the Bohai Sea. Similar circulation structures were found in the middle of the Bohai Sea, around Changxing Island and in the north of the Bohai Strait during winter and summer. The circulation in summer was stronger than that in winter.6sets of experiments were carried to find that the effects of wind and heat flux were more obvious than that of tides both in winter and summer. However, wind-driven circulation played an more important role in winter and thermohaline circulation was more important in summer. River discharge merely affected the area near the estuaries. Only considered the M2tidal constituent was not reasonable to study the lagrangian circulation current.The effects of the rectangular reclamation and the stream lined one on the circulation near the Changxing Island and the northern part of the Bohai Strait were studied with the3-D model. The comparison of the circulation structure between the case of original topography and the case of two forms of reclamation separately showed that the reclamation worked to strengthen the anticlockwise circulation near the Changxing Island in winter and to weaken the anticlockwise circulation in summer. The ability to transport water into and out of the Bohai Sea of the local waters were weakened to a certain extent. The rectangular reclamation affected the particle trajectories more obviously than the stream lined one in the north of Bohai Strait. In addition, the effects of the rectangular reclamation on the circulation in the local waters were more obvious than those of the stream lined one.