FY 1980

Vertical wave number spectra of temperature fine structure in the equatorial Pacific

Hayes, S.P., and C.J. Powell

J. Geophys. Res., 85(C7), doi: 10.1029/JC085iC07p04029, 4029–4035 (1980)

We report observations of vertical fine structure in temperature along a meridional section from 10°N to 2°S at 125°W in the eastern Pacific. Structures are studied in two depth intervals, 300-600 m and 690-990 m, which are below the major influence of the surface currents and the equatorial undercurrent. On the basis of the TS relationship and the reasonably linear temperature and density profiles in these depth intervals, temperature fluctuations are used to infer vertical displacement fluctuations. We observed that vertical displacement spectra at the northern end (5°N to 10°N) of the section are consistent with mid-latitude observations. At the equator the spectral level increases by almost 1 order of magnitude. Displacement spectra from the two depth intervals scale in a manner consistent with a WKBJ approximation. The increase is more pronounced for wave lengths longer than 10 m. From a 13 hour time series on the equator, we observed that the increased variance at high wave number (k > 0.02 cycle m) was associated with high-frequency changes (f > 0.08 cph), while the low wave number variance was associated with lower frequencies.