2. Field Studies of Non-Linear Internal Waves in Lakes on the Globe

This chapter is devoted to the experimental techniques commonly applied in field studies of nonlinear internal waves in lakes of the world. It consists of four sections. The first attempts an overview of internal waves in many lakes on the globe and provides a summarising sketch of common measuring techniques and methods of graphical representation of collected results. The second takes a closer view on experimental methods of field observation, most being invasive, but we equally also address the modern remote-sensing techniques, which open promising, perhaps still challenging, procedures allowing a closer look at internal wave phenomena. More substantially, the specific features of the patterns of manifestation, i.e., generation and dissipation of nonlinear internal waves in lakes of different size and shape under various sets of environmental conditions, are considered. It is shown that planning experiments on nonlinear internal waves in large lakes are a far more challenging task than for smaller lakes since the range of thermodynamic processes and phenomena is much more complex, and so is the set of hydro-meteorological conditions (forcing) in stratified lakes. The third section focuses on internal wave dynamics of Lake Onego and its internal wave response during the summers of 2004/2005 and presents an exploitation of the data during the two summer field campaigns in the context of internal wave processes. The field experiments performed with the intention to investigate the generation and dissipation of nonlinear internal waves in Lake Onego are described in detail. These data are in the fourth section compared with models of nonlinear waves, which rounds out this chapter on internal waves in Lake Onego.