The Numerical Simulation Of The River Plume And Salinity Front In The Pearl River Estuary During The Dry Season

Some scholars indicated that the plume front along west coast is the significant hydrodynamic feature of the Pearl River estuary during the winter dry season. Until now, the study about plume and salinity front of the Pearl River estuary is few. The plume and salinity front is the important bio-geochemistry zone in the estuary, it greatly affects the sedimentation and topography evolution of the estuary, and the convergence of the front is benefit to gather pollutants which has great effect to the protection of environment. Consequently, it is necessary to do more research about plume and salinity front in the Pearl River estuary.In this paper, a high-resolution estuary-river integrated 3D circulation model FVCOM was established for the river plume in the Pearl River estuary(PRE). The spatial varied wind field which calculated by Weather Research and Forecasting Model is applied to the model. The results of the model is matched with the observations very well. It demonstrated that the model could predict a very accurate hydrology and hydrodynamic feature of the river plume and fronts in the Pearl River estuary.The detailed features of the plume and salinity fronts in the Pearl River estuary are analyzed with the model. Based on the salinity、dynamic and energy input characteristics of the water zone, the plume water can be divided into three parts: Riverine plume, estuarine plume and coastal plume. Three salinity fronts are formed between the boundaries of the three plumes each other and coastal water. The features and structures of the three plumes and fronts are highly variable with the tidal cycle both at surface and bottom.To survey the dynamic factors of the formation of the three plumes and salinity fronts, we do several numerical experiments. The results indicated that : 1) The riverine front(first front) in the pearl estuary has complicated dynamical feature, it’s formation is associated with river discharge, tide and wind.But the riverine discharge is the main reason of the formation of the riverine front. 2) The Ekman transport caused by the northeast monsoon is the main reason of the formation of the estuarine front(second front). 3) The coastal front(third front) is the interface of the plume water and coastal water, so it is always be here regardless the tide and wind. But it is sensitive to the wind. When the wind stress to be increased, the coastal front will be stronger, and be more close to the west shore. 4) The tidal stirring will weaken the effect of the wind. In other words, the existence of tide will be weaken the strength of the estuarine front and coastal front. But tide is very important to the formation of the local plume around the qi’ao island which appears at ebb and belong to the first front.