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，也是推动垂直混合的关键过程。在康斯坦茨湖，能量最强的高频波通常是在盆地尺度内开尔文波陡峭的前沿产生的孤立波。该项目涉及的主要问题是层结、内部锋面的特征和湖泊地貌测量如何影响康斯坦茨湖内部锋面孤立波列的出现和性质，这些孤立波和波前在开放水域的湍流中损失了多少能量，以及孤立波列的性质沿其传播路径是如何变化的。这项研究将结合对几年来高频温度时间序列的现有数据的分析和一项新的现场实验。作为经验研究的补充，将通过数值模拟求解具有空间变化系数的Korteweg-de Vries/Korteweg-de Vries-Burgers方程来模拟内部锋面的孤立波列。由统计分析提供的孤立波幅度、孤立波出现频率的空间差异以及孤立波通过过程中能量耗散的经验估计，将为评估孤立波在从盆地尺度运动到湍流的能量通量中的作用以及在开放水域中的混合提供依据。

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.