| The winter storm event, a familiar synoptic phenomenon in winter of the Bohai Sea and Yellow Sea, has the important effect on the circulation and sediment transport. However, few works has been carried on this subject by high resolution wind stress, heat flux and wave. Thus in this study, a 3-D numerical model, ECOMSED, coupled with shallow sea wave model, SWAN was used to study the effect of winter storm event on the circulation and sediment transport, taking the event on 19 to 21 December in the winter of 1999~2000 as an example. The model was driven by 6-h wind stress and surface heat flux in the Bohai Sea and Yellow Sea. Due to the Ekman transport, water was accumulated along the Subei and water level decreased over 50 cm to 100 cm in the Liaodong Bay and north Yellow Sea. Almost all the area the water temperature decreased 2 to 4oC, while the water temperature in the southeastern Yellow Sea increased 1oC at the bottom which indicated the effect of heat advection due to the strengthen Yellow Sea Warm Current. The mud ridge to the southeast of Shandong Peninsula can be described as result of winter storm event. High concentration sediment was transported from the northeast of the Shandong Peninsula to the southeast and deposited in the area of weak circulation. 0.5cm mud accumulation can be found to the southeast of Shandong Peninsula due to one storm event. And the net sediment flux is 3 and 4 times more than the effect of climitological wind, respectively from the Bohai Strait to Yellow Sea and from north Yellow Sea to the south.During the winter storm event, the phase of water level and circulation are 0.5 and 1 day lagged to the wind, respectively. Furthermore, field observation in the Yellow Sea also showed the 12 to 48 hours phase difference between wind and northern currents. The numerical experiment indicated that the positive pressure gradient, due to water accumulation in the south Yellow Sea, was the main force to drive the northward flow. Water adjustment made the maximum northward current lag behind the maximum northerly wind by 1day. And it took almost 10 and 20 days respectively for the surface slope to adjust to a stable state as the wind started and stopped. The combination effect of weak speed and phase lag of the wind driven compensation current can be used to explain the one month phase delay between the beginning/ending of winter northwesterly wind and the emergence/disappearance of the warm tongue in the Yellow Sea detected from the satellite SST data. And the sensitivity experiments indicated that the Coriolis force and topography played major roles in the westward shift path of the Yellow Sea Warm Current in the Yellow Sea.Different effect of heat advection and surface heat flux on the Yellow Sea heat budget in winter was still in heat debate. There was heat loss all over the Yellow Sea during winter and the winter averaged heat content change decreased with an area averaged rate of - 106 W m-2. Comparing with the similar horizontal distribution and winter averaged value of surface heat flux of -150 W m-2 averaged from four data sources, we conclude that surface heat flux played a dominant role in the YS heat content change during winter, while the effect of positive heat advection of the YSWC can account for between 17 % and 41% of the YS heat content change, calculated by four different heat flux data sets. During a winter storm event in winter of 1999 to 2000, the heat content change is -241Wm-2, while the effect of surface net heat flux is -281Wm-2, thus the heat advection transported 40Wm-2 heat into the Yellow Sea, which is two times more than the climatologic effect.On the one hand, sediments can be resuspended and transported by tidal current. On the other hand, tidal current can be affected by high sediment concentration by stratified bottom boundary layer. Tidal shear front off the Yellow River mouth is the result of tidal dynamics. Thus the mechanism of this front and its effect on the sediment distribution off the river mouth were studied. The sensitivity numerical experiments showed that the topography with a strong slope off the Yellow River mouth was a determining factor for the front generation, and a parallel orientation between the major axes of ellipses and co-tidal lines of maximum tidal current was a necessary condition. While the bottom friction and the river runoff had no effect on the front location but affected the front intensity, the front generation was not sensitive to the coastline variation. The study concluded that the bottom slope off the river mouth induces a strong variation in the bottom stress in a cross-shore direction, which produces both maximum phase gradient and sediment concentration variability across the tidal shear front. As for the sediment distribution in the Bohai Sea and Yellow Sea, it is high sediment concentration in the shallow water along Subei, Korea, in Bohai Strait and Liaodong Bay, which are resuspended by strong tidal currents. The high sediment concentration can stratify the bottom boundary layer, reduce the bottom shear stress then damp the sediment resuspension. Therefore, the sediment concentration was significantly reduced in above places, and the tidal amplitude and phase were increased and delayed.Therefore, based on the simulation of the circulation and sediment transport during the winter storm event, the formation of mud ridge to the southeast of Shandong Peninsula was described in dynamic method. The phase lag of Yellow Sea Warm Current to the northerly wind and westward shift path were discussed. Based on the satellite data and numerical simulation, the heat budge of Yellow Sea and Bohai Sea in winter was studied by discussing the effect of heat advection and surface heat flux. The generation mechanism of tidal shear front off the Yellow River mouth was first studied and its effect on the sediment distribution off the river mouth was also described. Although the effect of high sediment concentration on the tidal dynamics was studied in this work, it still needs further detailed study. |
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