Internal wave weather in a stratified lake

Thermistor chain data collected in Lake Biwa (Japan) during a period of str ong stratification were used to determine the nature of the water column re sponse to wind forcing. The evolution of the basin-scale waves in the lake were reproduced in three-dimensional numerical simulations and the time var iability of the internal wave spectrum is discussed based on spectral analy sis of the thermistor chain records. Severe winds associated with the passa ge of three typhoons during the sampling period excited basin-scale Kelvin and Poincare waves, which, by interaction with the topography of the lake a nd non-linear effects, generate trains of high-frequency internal waves. Ti me-frequency analysis of the temperature signals suggests that the omega(-2 ) slope of the internal wave spectrum is probably the result of the composi tion of groups of waves with high intermittence travelling through the wave guide. The observed rapid decay of internal wave energy after severe wind events seemed to be due mostly to high dissipation at the sloping boundarie s of the lake.