|
Title: Horizontal structure and excitation of primary motions in a strongly stratified lake Authored by: Shimizu, K., Imberger, J. and Kumagai, M. Abstract:
The horizontal structure and excitation of basin-scale internal waves and gyres in Lake Biwa were investigated. A normal mode analysis in the horizontal plane was extended to a layer-stratified basin with irregular bathymetry in order to obtain the horizontal modal structure and a set of decoupled evolutionary equations for each individual mode. It is shown that the horizontal structure of the basin-scale internal waves consists of cyclonic (anticyclonic) internal waves in separate elliptic cells, each following the dispersion relationship of Kelvin (Poincaré) waves in an elliptic basin. The decoupled equations for the amplitude of individual modes were used to show that even spatially uniform winds can preferentially excite internal wave modes depending on the wind direction. On the other hand the spatial distribution of wind stress curl over the lake primarily determines the horizontal structure of gyres that are formed in response to the stress. Comparison of the modal analysis results with results from a three-dimensional hydrodynamic simulations which included non-linear effects, damping and a continuous stratification, showed that the modal equations accurately predicted the horizontal structure of the induced internal motions (waves and gyres) and the amplitude of the motions in the early stages of the excitation of the gyres, but the amplitudes progressively deviated with time.
Reference: Shimizu, K., Imberger, J. and Kumagai, M., 2007, Horizontal structure and excitation of primary motions in a strongly stratified lake, 52: 2641-2655 Keywords: internal waves, ELCOM, Kelvin, Poincare, gyres |
Publications options:
Browse by year: |
