Marine Science Faculty Publications

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The kinematics of planetary waves originating from instability of the nearsurface equatorial currents are reported on using velocity measurements from an array of acoustic Doppler current profilers deployed in the equatorial Pacific during the Tropical Instability Wave Experiment. A distinctive wave season was observed from August to December 1990, with wave energy confined primarily above the core of the Equatorial Undercurrent. Particle motions in the horizontal plane are described by eccentric ellipses oriented toward the north, but tilting into the cyclonic shear of the South Equatorial Current. The tilt is maximum near the surface just north of the equator and decreases to the south and with depth. The distribution of wave variance is narrowband in both frequency and zonal wavenumber, with central period, zonal wavelength, and westward directed phase propagation estimated to be 500 hours, 1060 km, and 59 cm s(-1), respectively. Neither the meridional nor the vertical wavenumber component is statistically different from zero. These results generally agree with previous findings on tropical instability waves from the Atlantic and Pacific Oceans, and, in the undersampled arena of geophysical measurements, they provide an example where statistical inference is supported by an ensemble of independent measurements.

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Journal of Geophysical Research, v. 100, issue C5, p. 8677-8693

Copyright 1995 by the American Geophysical Union.