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Seasonal differences in the evolution of damped basin‐scale internal waves in a shallow stratified lake
Author(s) -
Shimizu Kenji,
Imberger Jörg
Publication year - 2010
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2010.55.3.1449
Subject(s) - internal wave , dissipation , mechanics , amplitude , forcing (mathematics) , boundary layer , kelvin wave , physics , geophysics , infragravity wave , geology , atmospheric sciences , meteorology , mechanical wave , wave propagation , longitudinal wave , quantum mechanics , thermodynamics
The evolution of damped basin‐scale internal waves was investigated using a modal analysis for layer‐stratified rotating lakes. A simple model for homogeneous oscillatory boundary layers was incorporated into the modal analysis to predict damping rates of individual internal‐wave modes, enabling the prediction of their evolution under wind forcing and bottom friction. Application of the method to Lake Kinneret indicated a different dynamic balance in summer and spring, despite the continuous presence of large amplitude internal waves in the two seasons. In summer, strong diurnal winds continuously excited the dominant Kelvin waves, but the relatively strong damping (e‐folding damping times ∼ 3 d) suppressed their amplitudes. In spring, wind forcing was again strong, but intermittent, and it was weaker damping (e‐folding damping times ∼ 10 d) that allowed the dominant Poincareé waves to persist until the next wind event. The significant difference in the damping times was due to the difference in the periods and the structure of the internal waves as well as the bottom boundary‐layer thickness, which limited the Ekman transport and energy dissipation within the boundary layer.