Properties of solitary wave trains at internal fronts in Lake Constance

在湖泊和海洋的温跃层中，高频内波被认为是湍流动能的主要来源和驱动垂直混合的关键过程。在康斯坦斯湖，能量最高的高频波通常是在盆地尺度内开尔文波的陡坡前缘产生的孤立波。本项目主要研究的问题是：分层、内锋特征和湖泊形态如何影响康斯坦斯湖内锋孤立波列的发生和性质，这些孤立波和波前在开放水域湍流中损失了多少能量，以及孤立波列的性质如何沿着其传播路径变化。这项研究将把几年来高频温度时间序列的现有数据分析与一项新的实地试验结合起来。通过数值模拟求解具有空间变化系数的Korteweg-de Vries / Korteweg-de Vries- burgers方程来模拟内锋面的孤立波列，以补充实证研究。统计分析提供的孤立波振幅的空间差异、发生频率以及孤立波通过过程中能量耗散的经验估计，将为评估孤立波对从盆地尺度运动到湍流的能量通量和对开放水域混合的作用提供依据。

In the thermocline of lakes and oceans high-frequency internal waves are considered to be the major source of turbulent kinetic energy and a key process driving vertical mixing. In Lake Constance the most energetic high-frequency waves are typically solitary waves generated at the steepened front of the basin scale internal Kelvin wave. The main questions addressed in this project are how stratification, the characteristics of the internal front and lake-morphometry affect the occurrence and properties of solitary wave trains at the internal front in Lake Constance, how much energy is lost from these solitary waves and the wave front to turbulence in the open water and how the properties of solitary wave trains change along their path of propagation. The study will combine the analysis of existing data on high-frequency temperature time series from several years with a new field experiment. The empirical investigations will be complemented by numerical modeling solving the Korteweg-de Vries / Korteweg-de Vries-Burgers equation with spatially varying coefficients to simulate solitary wave trains at the internal front. The spatial differences in solitary wave amplitude, the frequency of the occurrence of solitary waves provided by the statistical analysis and the empirical estimates of energy dissipation during the passage of solitary waves will provide a basis to assess the role of solitary waves for the energy flux from basin scale motion to turbulence and for mixing in the open water.