磨刀门河口环流与咸淡水混合层化机制

Estuarine circulation and mechanism of mixing and stratification in the Modaomen Estuary

为研究磨刀门盐水混合层化特征,基于SCHISM模型,建立了三维盐度数值模型,根据实测资料对其进行验证。结合水体势能异常理论,对枯季磨刀门河口混合层化的时空变化特征及深槽与浅滩的层化机制差异进行分析。结果表明:磨刀门河口小潮时水体层化最强,中潮时水体层化最弱,且拦门沙至挂定角段水体层化始终较强。磨刀门深槽水体层化主要受纵向平流、纵向水深平均应变和垂向混合影响,而浅滩水体层化则受横向平流、横向水深平均应变和垂向混合影响;磨刀门河口表、底层水体湍动能耗散率较高,而中间水层存在低耗散区,且涨潮时湍动能耗散率比落潮时大。

To study the characteristics of mixing and stratification in the Modaomen Estuary, a three-dimensional nu- merical salinity model was established based on SCHISM and then calibrated against measured data. Combined with the theory of the water potential difference, the temporal and spatial variation characteristics of mixing and stratification in the dry season and stratification mechanism of a deep channel and shoal were studied. The results show that water stratification is the strongest during the neap tide and is the weakest during the medium tide. Saltwater from the sandbar to Guadingjiao is always highly stratified. Along-channel advection, along-channel depth-mean straining and vertical mixing are the main factors that influence the water stratification of the deep channel. While cross-channel advection, cross-channel depth-mean straining and vertical mixing are the main factors that influence the water stratifi- cation of the shoal. In addition, there is a relatively high dissipation of turbulent kinetic energy （TKE） at the surface and bottom of the water column and low TKE dissipation at the middle of it. There is an asymmetric flood/ebb tidal distribution, with the flood higher than the ebb.