珠江口外羽状锋面的湍流混合特征

The Pearl River plume(PRP) front separates the diluted water and South China Sea(SCS) water. It plays key roles in the dynamics, thermodynamics, environment, transport of material and marine culture in the northern SCS, through spreading and enhanced mixing. The spreading processes of PRP are widely studied, but the mixing processes are still unclear in the PRP front area. Based on field data and satellite data, the present project aims to reveal the mixing processes in the PRP front zone. The three-dimensional structures of temperature, salinity, velocity and the turbulent dissipation rate are firstly observed using high-resolution equipment. Then the tidal averaged velocity and turbulent velocity are estimated to quantify the vertical mixing. Through theoretical analysis, we will analyze the environmental factors (e.g., runoff, tide and wind) in the turbulence, and then set up a mixing parameterization model. Finally, we will discuss how the parameterization influences the PRP front. This study is very helpful for us to understand the transport of material across the PRP front, and is expected to support the simulation of the oceanic current.

珠江口外羽状锋面是珠江冲淡水与南海水相遇的狭窄过渡带，其羽状流通过扩散与湍流混合对南海北部陆架区动力、热力、生态环境、物质输运、海洋养殖等方面有着重要的影响。目前对珠江口外羽状流扩散的研究比较多，而对锋面区域混合特征的研究还比较薄弱。 本项目拟在前期工作的基础上，针对珠江口外的羽状锋面区域， 基于航次观测与遥感数据，观测珠江口外羽状锋面温度、盐度、流速、湍动能耗散率的三维结构，估算平均流结构与湍流微结构的湍动特征量，分析其层化与混合特征；理论分析环境因素(潮差、风、径流)对该区域湍流混合的影响,建立珠江口外羽状锋面区域的湍流混合参数化方案，探究参数化对锋面强度的影响。本项目针对锋面区域给出局域性的湍流混合分布特征及参数化方案，有助于我们理解锋面的跨物质输运，并有希望对数值模拟南海环流提供技术支持。

珠江口外羽状锋面是珠江冲淡水与南海水相遇的狭窄过渡带,其羽状流通过扩散与湍流混合对南海北部陆架区动力、热力、生态环境、物质输运、海洋养殖等方面有着重要的影响。目前对珠江口外羽状流扩散的研究比较多,而对锋面区域混合特征的研究还比较薄弱。本项目在前期工作的基础上,针对珠江口外的羽状锋面区域, 基于航次观测与遥感数据,观测了珠江口外羽状锋面温度、盐度、流速、湍动能耗散率的三维结构,估算平均流结构与湍流微结构的湍动特征量;理论分析环境因素(潮差、风、径流)对该区域湍流混合的影响。发现羽状流内部湍流混合强度大于锋面处，通过悬浮泥沙动量平衡方程，发现平流输运对泥沙起第一大作用，而湍流混合对泥沙悬浮起着第二大作用。本项目针对锋面区域给出局域性的湍流混合分布特征及泥沙悬浮机制,有助于我们理解锋面的跨物质输运,并有希望对数值模拟南海环流提供技术支持。