Tj. Boyd et al., HIGH-FREQUENCY INTERNAL WAVES IN THE STRONGLY SHEARED CURRENTS OF THEUPPER EQUATORIAL PACIFIC - OBSERVATIONS AND A SIMPLE SPECTRAL MODEL, J GEO RES-O, 98(C10), 1993, pp. 18089-18107
Statistics of high-frequency (0.24.5 cph) fluctuations are derived fro
m moored upper ocean measurements of currents and temperatures at four
latitudes spanning the equator along 140-degrees-W. Some of the more
unusual statistics include (1) nonunity ratios of kinetic energy to po
tential energy; (2) nonunity ratios of zonal to meridional kinetic ene
rgy; (3) nonzero current-temperature coherence amplitudes, with depth-
dependent phases; and (4) high vertical coherence amplitudes, with app
roximately 180-degrees phases, between current measurements spanning t
he thermocline. A simple model of shear-modified internal waves is emp
loyed to gain insight into the causes of the latitudinal variability o
f the statistics. Much of this variability can be attributed to the ve
rtical advection of significantly different mean vertical shears by a
spectrum of internal waves. The statistics also suggest that the spect
rum of high-frequency internal waves in the upper equatorial Pacific d
iffers in important ways from canonical spectral models. The statistic
s are consistent with a model based on vertical modes which neglect ad
vection by the mean flow, provided the energy in the first mode is muc
h less than (about 0.3 times) that in the spectrum described by Garret
t and Munk (1972, 1975, 1979) and Munk (1981) and two to four times as
much energy propagates eastward as westward. Some of the statistics a
re inconsistent with the simple internal wave model examined, possibly
indicating contamination by mooring motion.