The propagation of long, first mode, baroclinic planetary waves in eddy-res
olving quasigeostrophic general circulation models is studied. Recent TOPEX
/Poseidon observations argue oceanic first-mode planetary waves move with s
peeds other than those predicted by simple theory. These data have prompted
theoretical analyses of wave propagation in a mean flow, with the results
suggesting mean shear can have a controlling effect on the planetary wave g
uide. Some of the predicted effects appear to be relevant to the observatio
ns, while others are less obvious. This, coupled with other explanations fo
r the observations, motivates the calculations.
Based on these experiments, the authors suggest that the predicted effects
of mean shear on wave propagation are consistent with those computed in a f
ully geostrophically turbulent ocean. These are that a two-layer model miss
es the dominant component of long-wave interaction with a mean flow, a thre
e-layer model captures this interaction qualitatively, and the correction t
o wave propagation is in the direction opposite to the mean flow. Quantitat
ive comparisons between the theory and the numerical experiments are good i
n the northern latitudes and questionable in the southern latitudes. Reason
s for the southern discrepancy are offered.