HIGH-FREQUENCY INTERNAL WAVES IN THE STRONGLY SHEARED CURRENTS OF THEUPPER EQUATORIAL PACIFIC - OBSERVATIONS AND A SIMPLE SPECTRAL MODEL

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.