Miller, A. J., 1992:
On forced barotropic vorticity oscillations
Journal of Physical Oceanography,
Forced, nonresonant barotropic response at low frequencies (omega much less than f) and large scales(L approximately
f/beta) can be written in terms of a streamfunction, which is similar to the quasigeostrophically derived steamfunction.
However, the "nearly equilibrium" forced vorticity equation is valid on the planetary length scale and is influenced not
only by the vortex stretching induced by the driving mechanism (tides, atmospheric pressure, or Ekman-pumping
displacement) but also by beta-coupling to the divergent velocity field of the nearly equilibrium response. A similar
result follows for topographic coupling, albeit on the topographic length scale.