Three-dimensional wind-induced baroclinic circulation in rectangular basins

We present results of various circulation scenarios for the wind-induced currents in two vertically stratified rectangular basins of constant depth with different sizes; these are obtained with the aid of a semi-spectral semi-implicit finite difference code developed in Haidvogel DB, Wilkin JL, Young R. J. Comput. Phys. 94 (1991) 151-185 and Wang Y, Hutter K. J. Comput. Phys. 139 (1998) 209-241. Our focus is to see whether the code allows reproduction of the many well-known processes exhibited in stratified waters of a lake basin on the rotating Earth. Often, the internal dynamics exhibits Kelvin- and Poincare-type oscillations, whose periods depend upon the stratification and the geometry of the basin and which persist for a long time, the attenuation being the result of the turbulent dissipation mechanisms. It is shown that the numerical dissipation of our code can be sufficiently restricted that such wave dynamics obtained with it is realistically persistent for typical time scales of physical limnology. Direct responses to wind forcing and the oscillating behaviour after wind secession are studied and numerical results are illustrated for longitudinal and transverse winds, respectively. By solving the eigenvalue problem of the linearized shallow water equations of two-layered closed rectangular basins, the interpretation of the oscillations as Kelvin- and Poincare-type waves is corroborated. (C) 2000 Elsevier Science Ltd. All rights reserved.