Numerical simulation of construction project environmental impact on the tides and tidal currents in Aojiang offshore of Wenzhou

This paper have collected the measured tides and certain tidal current data in different stages of many projects during past three to five years near the Aojiang River. The harmonic method is used to analyze tide and tidal current data observed at five stations in the sea adjacent to Aojiang River. The results show that the tide is mainly regular and semidiumal in the sea near Aojiang of Wenzhou. The tidal amplitudes of M2 constituent are between 170 cm - 193 cm and the lags are between 260~ - 280~, According to the comparison of analytical results of harmonic constants of these stations in 2007, 2010 and 2011, the maximum change of tidal amplitudes and phase-lag range for the main semidiurnal tides （M2, $2, N2）, the diurnal tide （K1, O1） and the shallow water tide （M4, MS4, M6） are 1.8 cm - 4.4 cm and 3~ - 7~, respectively. After analyzing the tide and tidal current characteristics of Aojiang River, this paper uses an unstructured grid and Finite-Volume Coastal Ocean Model （FVCOM） to test the results of simulation. The simulated results agree well with the measured data. The new shoreline and depth which are produced by the construction projects closed in important major years, and the tide and tidal current field for the new shoreline and depth are constructed, which describe the superimposed influences of construction engineering in Aojiang estuary.

Three-dimensional numerical simulation for tide and tidal current in the Beibu Gulf

By means of three dimensional POM model,which computes the eddy viscosity coefficient based on two order turbulent closed model,the tide and tidal current in the Beibu Gulf are simulated with fine grid.In the computed region,six islands are considered and the bottom friction coefficients are taken to be various values from the difference of sea region.Acquired tidal harmonic constants are compared with that of 81 tidal observatories.The absolute mean error of K 1 constituent amplitude is 4 6 cm and of the lag is 9°.The absolute mean error of O 1 constituent amplitude is 5 6 cm and of the lag is 7°.The absolute mean error of M 2 constituent amplitude is 6 2 cm and of the lag is 15°.The tide,tidal current,residual water level and tide induced residual current,as well as the vertial distribution of horizontal velocity in this sea region are analysed by the simulated results.

A detection model of underwater topography with a series of SAR images acquired at different time

underwater topography is one of oceanic features detected by Synthetic Aperture Radar.Underwater topography SAR imaging mechanism shows that tidal current is the important factor for underwater topography SAR imaging.Thus under the same wind field condition,SAR images for the same area acquired at different time include different information of the underwater topography.To utilize synchronously SAR images acquired at different time for the underwater topography SAR detection and improve the precision of detection,based on the detection model of underwater topography with single SAR image and the periodicity of tidal current,a detection model of underwater topography with a series of SAR images acquired at different time is developed by combing with tide and tidal current numerical simulation.To testify the feasibility of the presented model,Taiwan Shoal located at the south outlet of Taiwan Strait is selected as study area and three SAR images are used in the underwater topography detection.The detection results are compared with the field observation data of water depth carried out by R/V Dongfanghong 2,and the errors of the detection are compared with those of the single SAR image.All comparisons show that the detection model presented in the paper improves the precision of underwater topography SAR detection,and the presented model is feasible.

Modelling of the barotropic processes in the Bohai Sea

The barotropic processes of tides, tidal currents, wind-driven currents and the interaction of winds andtides in the Bobai Sea are investigated with a three-dimensional shelf sea model. The tides and tidal currents are wellsimulated. The main characteristics of tides and tidal currents, such as the types of tides and tidal currents, co-tidaland co-range charts, co-current charts, tidal ellipses, mean tidal currents and tidal residual currents are presented. Apair Of cyclonic and anticyclonic headland eddies in the northern Bohai Straits is discovered. The tidal currents have little vertical structure except close to the sea bottom. Driven by strong winds, the currents have a significant three-dimensional structure. In response to coastal geometry and bottom friction, the wind drift in the upper layers is in the direction of the wind or slightly to the right. In depth, considerable compensating currents maintain a circulation balance. The interaction of winds and tides is locally strong. The oscillating tidal currents play a role of dissipating energy. Thus the usual purely wind-driven currents in the area of weak residual tidal currents are often overestimated in theabsence of tides.