Dissertation
Dissertation > Environmental science, safety science > Environmental pollution and its prevention > Marine pollution and its prevention

Numerical Study about Circulation in Summer and Its Impact on the Drift of Enteromorpha Prolifera in the Western Part of South Yellow Sea

Author YuXiaoJie
Tutor LouAnGang
School Ocean University of China
Course Environmental Science
Keywords FVCOM south Yellow Sea summer circulation current enteromorpha prolifera
CLC X55
Type Master's thesis
Year 2011
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From the summer of 2008 till now, there have been three times when large number of enteromorpha prolifera springs up in summer in the western part of south Yellow Sea, whose ranges cover the whole western part of the south Yellow Sea. After forming in the south, the enteromorpha prolifera drifts to the north under the effects of tidal current and the current induced by wind, and accumulates abundantly around Qingdao, Yantai and Weihai, and has a bad impact on the marine ecology, fisheries and tourism here. Especially the one happened in 2008 when lots of enteromorpha prolifera gathered in the coast of Qingdao made serious ecological hazard and ecomony loss, and affected the scenic landscapes and beach tourism revenue. Therefore, it’s necessary to establish a related model to simulate the tidal current and circulation current in summer in the western part of the south Yellow Sea and to track the path of the enteromorpha prolifera based on the current, in order to provide theoretical basis and technical support for the revelent units to intercept and catch the enteromorpha prolifera timely.In this thesis, firstly a model of tide and wind-induced circulation in the western part of the south Yellow Sea is established. The three-dimensional oceanic numerical model-FVCOM is used to simulate the M2 tide and the monthly wind-induced circulation in June of 2009. Accordingly, the tidal-induced Euler residual current and wind-induced circulation are simulated respectively, and also they are verified. Subsequently both the M2 tide and the wind are considered to simulate the circulation structure in June, 2009. Accordingly, the tidal-and-wind-induced circulation is simulated. By comparing the velocity and circulation of the model results with that of the observational data in some representative points in the computed area, it can be seen that the simulated results could reflect the circulation situation in this area accurately.Based on the tidal current and circulation current simulated above, the Lagrange particle track method is used to predict the track path of the enteromorpha prolifera in south Yellow Sea in the summer of 2009. Three numerical experiments are taken into account, including the effect of pure tidal current, tide and monthly wind in June, tide and daily wind in June. Through comparing the different drift results of the three experiments, it can be seen that: pure tidal current makes the particle move in a small cycle range, resultingly the ultimate destination depends on the tidal residual current; when both tide and monthly wind are considered, the particle basically moves in the direction of some degrees right from the wind direction, meanwhile makes periodically reciprocating motion under the influence of tide; when under the effect of tide and daily wind, the overall trajectory of the particle is still in accordance with the direction of the wind, and presents periodically reciprocating motion under the influence of tide, but in relatively tortuous path, mainly because the speed and direction of daily wind are changing constantly. In the end, through comparing the three instances above with the observational data, it can be seen that the third instance is relatively closer to the reality.The circulation current model and the drift model of enteromorpha prolifera in western part of south Yellow Sea in summer established in this study not only make a more explicit description about the tide and circulation structure in this area, and could also predict the drift path of the enteromorpha prolifera accurately. Therefore, it could provide theoretical basis and technical support for the revelent units to intercept and catch the enteromorpha prolifera timely, and have profound theoretical and significant practical meanings.

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