Numerical Simulation of Hydrodynamic and Water Properties in the Yellow Sea: Tidal Effects on Changjiang River Diluted Water

Chang S. Kim, Hak Soo Lim, Dong-Young Lee
Korea Ocean R&D Institute, South Korea

and

Peter Chu
Naval Postgraduate School, Monterey, CA USA

The Yellow Sea is characterized by relatively shallow water depth, varying range of tidal action and very complex coastal geometry such as islands, bays, peninsulas, tidal flats, shoals etc. The dynamic system is controlled by tides, regional winds, river discharge, and interaction with the Kuroshio. The circulation, water mass properties and their variability in the Yellow Sea are very complicated and still far from clear understanding. Numerical simulation of using the ROMS model was conducted for monthly variation of circulation and water property in the Yellow Sea. This study demonstrates the applicability of the terrain-following ROMS model to major processes in the Yellow Sea such as distinct features of different circulation patterns, dilution of seawater due to fresh water discharge from major rivers, exchange between coastal waters and shelf waters across the tidal fronts etc.

The model adopts curvilinear grid with horizontal resolution of 3 –5 km and 20 vertical grid spacing confirming to relatively realistic bottom topography. The model was initialized with the LEVITUS annual climatological data and forced by tides and by the monthly mean air-sea fluxes of momentum, heat and fresh water derived from COADS. On the open boundaries, climatological temperature and salinity are nudged every 20 days for data assimilation.

In recently submited paper, we have simulated the general dynamic features of the circulation, temperature and salinity variation throughout the year. By applying the climatological forcing, the simulated results have been verified with long-term observed data , yielding a quite reasonable and acceptable features dominant in the Yellow Sea such as major water masses and reported currents. In this study we simulate the major effects of tidal actions on the Changjiang River Diluted Water. The horizontal dispersion and vertical structure of the buoyant flow are significantly affected by tidal action. We also compare the different dynamic features forced only by climatological forcing and by added tidal forcing. By adding the tidal forcing, it clearly shows the evolution of tidal fronts on the shelf break in spring and in autumn.