A SIMPLE-MODEL FOR THE SYMMETRY PROPERTIES OF NONLINEAR WIND-DRIVEN OCEAN CIRCULATION

It is shown that the symmetry properties of barotropic nonlinear wind driven ocean circulation, as presented in the numerical simulations of Veronis (1966a,b), can easily be derived analytically for large Ekman number, the so-called ''small beta regime'', and for any strength of the nonlinearity, by a perturbation expansion in the inverse Ekman num ber. The solution is a superposition of a vorticity monopole, dipole a nd quadrupole, the symmetry properties of which are qualitatively the same as those of the Veronis' sequence. It is also shown that the Vero nis' sequence does not lead to the inertial Fofonoff (1954) mode, but that the latter is the limit of another sequence in the parameter plan e spanned by the Rossby and Ekman numbers.