| Wave is one of the most important factors in the ocean. It is necessary to further understand the wave characteristics for designing and constructing marine structures. In addition, the interactions between deformed/broken waves and tides in coastal waters will result in complex nearshore currents, which will have important effect on water exchange and sediment movement, and will further affect the mass transport and topography in coastal areas. With large-scale coastal engineerings being constructed in the Bohai Sea, especially along the coast of the Bohai Bay, it is quite necessary to investigate the wave characteristics of this region and the impact of waves on water exchange of nearshore waters to support the design of coastal structures as well as the protection of eco-environment.In this study, a set of numerical models were developed for simulating wave and current in the Bohai Sea, which include the tidal model based on the shallow water long wave equation, wave model SWAN(Simulating Waves Nearshore) based on wave action balance and the nearshore currents based on the concept of radiation stress. The factors affecting the results of SWAN model were analysized carefully, and then, the model was systematically calibrated using both the short-term and long-term field wind and wave data distributed at different stations throughout the whole Bohai Sea. A set of model parameters were abtained, which is applicable to the whole Bohai Sea. The numerical results by the calibrated SWAN model are in good agreement with the measured data both in different spatial scales and in different time range. The model for simulating nearshore current was verified using experimental data, and the results are in agreement with the experimental data.The calibrated SWAN model, driven by the corrected ECMWF wind field, was applied to investigate the wave characteristics in Bohai Sea. The wave field in the Bohai Sea was simulated for 20 years. The results show that, in general, both the spatial and seasonal distribution of wave heights and average periods obtained in this study are in consistent with the existed results. However, the values of the significant wave heights in some area are different to that obtained by other researchers, with the difference being 0.1m in the three major sea bays and 0.01 m to 0.1m in Bohai Center and the Bohai Strait.A water exchange model suitable for analyzing both global and local water exchange characteristics of a large-scale water body was developed by combining the particle tracking model based on random walk method and the characteristic time scales for describing water exchange such as residence time, exposure time and return coefficient. The movements the particles initially released in the Bohai Bay were simulated for three consecutive years, and then the water exchange characteristics of the Bohai Bay and the effect of waves on them were investigated through statistical analysis of the characteristic time scale and the residual current field. The results suggested that the overall water exchange in the Bohai Bay is weak, and wave affects the water exchange in Bohai Bay to some extent, which are more significant in the coastal region. Significant differences lies in the contributions of water in different regions to the water exchange of the entire Bohai Bay.Finally, the effect of the reclamation projects on water exchange characteristics of Bohai Bay was analyzed, considering the reclamation projects in the Bohai Bay that have been built and are underconstruction in recent years. The results show that the half-exchange time of the water of the Bohai Bay was shortened slightly by reclamation. The effect of reclamation on water exchange is much more significant on the water exchange throughout the coastal areas of the Bohai Bay, but not limited to the vicinity of the project regions. Regional differences are found in degree of the effects of reclamation on water exchange in different regions... |
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