Aj. Miller et al., THE FORTNIGHTLY AND MONTHLY TIDES - RESONANT ROSSBY WAVES OR NEARLY EQUILIBRIUM GRAVITY-WAVES, Journal of physical oceanography, 23(5), 1993, pp. 879-897
The fortnightly and monthly tides are discussed in the light of recent
sea level observations and numerical modeling results. Within the tid
e gauge network of the low-latitude Pacific, the fortnightly tide is s
hown to possess a large-scale phase lag of roughly 10-40 degrees. Alth
ough the nonequilibrium part of the fortnightly tide is traditionally
thought to be dominated by Rossby wave dynamics, it is shown, via glob
al shallow-water modeling studies, that this large-scale phase lag is
explicable in terms of remotely forced gravity waves whose origin is m
ainly in the Arctic Ocean. Although future observations outside the lo
w-latitude region of the Pacific may eventually reveal Rossby wave exc
itation, the fortnightly tidal signal in the tide gauge network at han
d appears to reveal at most only weak excitation of Rossby waves compa
red to the phase lag due to remotely forced gravity waves. The observe
d monthly tide appears to be only slightly closer to equilibrium than
the fortnightly tide. The reason for this remains unclear since the mo
nthly tide is less affected by the remotely forced gravity waves than
the fortnightly tide.