Internal Solitary Waves in Lakes – a Closure Problem for Hydrostatic Models

Laboratory experiments and field observations suggest that the degeneration of basin-scale internal standing waves into packets of solitary waves is an important mechanism for the transfer of energy within the internal wavefield in lakes. Since these shorter solitary waves break at the boundaries, this process provides a flux path from the wind to the turbulent benthic boundary layer. However, numerical models that make the hydrostatic approximation cannot simulate the evolution or propagation of internal solitary waves and therefore capture this important energy flux path. The feasibility of parameterising the important effects of solitary waves in hydrostatic models is discussed. Using a simple KdV model, some initial steps are suggested towards the development of such a solitary wave closure scheme.