Remote Sensing And Numerical Simulation Of Coastal Water Quality

The deterioration of marine water quality and unexpected oceanic disaster often make trouble to production and life of human beings, and result in substantial economic losses. In recent years, remote sensing has attracted more and more attention by monitoring the sea surface conditions in large scale and in near real time. Numerical simualtion is widely used in marine environmental study due to its flexibility in simulating and analyzing the oceanic phenomena and changes. However, remote sensing is seriously influenced by the weather condition and limited by the aerial survey or satellite operation period. Numerical simulation is obstructed in attaining the optimal parameter, the reasonable boundary or initial condition and verifying data. Therefore, it is of great significance to combine remote sensing and numerical simulation together for overcoming one's weaknesses by acquiring the strong points of the other. In this paper, these two methods are coordinated to study the water quality and unexpected oceanic disaster in the coastal areas. The following two parts are presented in this dissertation:The first part of this dissertation deals with the routine water quality in the Hangzhou Bay. Firstly, remote sensing monitoring results show that the distribution of area-source pollution in the bay is mainly controlled by the hydrodynamic factors. So, the pollutant trajectories and the half exchange time are simulated by the COHERENS model through Lagrangian particle tracking and Euler mass transport methods to analyze the physical self-purification capability in the bay. Secondly, the shipboard observation and numerical simulation combined with remote sensing are applied to study the warm water distribution and the influence of point-source thermal pollution on the water quality in the bay. Finally, the numerical SST (sea surface temperature) and chlorophyll-a results are used to make up the blank areas caused by cloud in the satellite images, which means that the mutual promotion of the remote sensing and numerical simulation play an important role on the coastal water quality study. It is shown that the point-source thermal pollution is not serious in the Hangzhou Bay. The area-source pollution is prone to accumulate in the northwest of the bay head area and the southeast of the bay mouth area. The bay is a typical high-nutrient-low- production place with high nutrient and suspended sediment concentration and low chlorophyll concentration. The second part of this dissertation deals with the unexpected oceanic disaster. The remote sensing and numerical simulation methods are applied to study the algal bloom in coastal area around Qindao City in 2008. Firstly, the development of the algal bloom is tracked by remote sensing. Then, the phytoplankton growth in spring in the Yellow Sea and the phytoplankton transportation from the middle part of the Yellow Sea are simulated by COHERENS ecological dynamics model and the Lagrangian particle track model. Lastly, the influence of wind on the algal growth is studied by the one-dimensional ecological dynamics model. The results imply that the phytoplankton blooms firstly in the central area of the Yellow Sea, while it is impossible to get the coastal area directly and induce the local algal bloom. The sustained wind before the algal bloom is helpful to the phytoplankton growth.