A Numerical Study of Transient Rossby Waves in a Wind-driven Homogeneous Ocean.

The primitive hydrostatic equations for a rectangular homogeneous ocean with a free surface on a beta-plane are integrated numerically for 60 days from an initial state of rest and an undisturbed depth of 400 m. A series of transient Rossby waves of approximately 2000 km length form in the central and eastern basin and undergo a well-marked life cycle as they propagate westward. The northward boundary current in the west and the countercurrents in the northwest may be identified as the first standing members of a continuing series of transients, with subsequent waves reaching progressively smaller maximum amplitudes. These transient oceanic long waves display a meridional asymmetry or tilt characteristic of a nonlinear poleward eddy transport of zonal momentum, much in the manner of their atmospheric counterparts. Near-geostatic equilibrium is maintained throughout, with the meridional Ekman flow of the order of a few centimeters per second. After a spin-up period of about 12 days, the surface potential and total kinetic energy display damped oscillations with the free period of approximately 16 days, with long surface gravity waves not significantly present. 47 pp. Ref.