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Barotropic response in a lake to wind-forcing

Wang, Yongqi and Hutter, Kolumban and Bäuerle, Erich (2001):
Barotropic response in a lake to wind-forcing.
19, In: Annales Geophysicae, (3), European Geosciences Union, pp. 367-388, ISSN 0992-7689, DOI: 10.5194/angeo-19-367-2001,
[Online-Edition: http://www.ann-geophys.net/19/367/2001/angeo-19-367-2001.htm...],
[Article]

Abstract

We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled. Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation.

Item Type: Article
Erschienen: 2001
Creators: Wang, Yongqi and Hutter, Kolumban and Bäuerle, Erich
Title: Barotropic response in a lake to wind-forcing
Language: English
Abstract:

We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled. Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation.

Journal or Publication Title: Annales Geophysicae
Volume: 19
Number: 3
Publisher: European Geosciences Union
Uncontrolled Keywords: Oceanography: general (limnology) – Oceanography: physical (Coriolis effects; general circulation)
Divisions: Study Areas
16 Department of Mechanical Engineering
16 Department of Mechanical Engineering > Fluid Dynamics (fdy)
Study Areas > Study Area Mechanic
Date Deposited: 30 Aug 2011 14:39
DOI: 10.5194/angeo-19-367-2001
Official URL: http://www.ann-geophys.net/19/367/2001/angeo-19-367-2001.htm...
Additional Information:

doi:10.5194/angeo-19-367-2001

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