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John M. Toole and Stanley P. Hayes

Abstract

An analysis of finescale horizontal-velocity shear and density data collected along 110°W longitude in the equatorial Pacific is presented. The measurements were made with the free-fall velocity–density profiler, TOPS. Twenty-five deployments are used to investigate the variability in the depth interval 150–900 m. In this interval the shear and strain fields are dominated by finescale structures. The extra-equatorial latitude band 4–10°N exhibits shear and strain spectra as well as Richardson number (Ri) statistics that are consistent with midlatitude internal-wave model predictions. Approaching the equator, an enhancement of shear and strain variance is found along with an accompanying increase in the occurrence of Ri less than ¼. Consistent with previous studies, the present measurement suggest that the 13°C thermostad is turbulently mixed. A high occurrence of Ri less than ¼ is also found below the thermostad and in the latitude range 2–4°S. The implications of these observations are discussed along the representativeness of the present measurements.

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Richard W. Reynolds, Ants Leetmaa, Klaus Arpe, Christopher Gordon, Stanley P. Hayes, and Michael J. McPhaden

Abstract

Surface wind analyses from three data assimilation systems are compared with independent wind observations from six buoys located in the Pacific within 8 deg of the equator. The period of comparison is 6 months (February to July 1987), with daily sampling.

The agreement between the assimilation systems and the independent buoy data is disappointing. The longterm mean differences between the buoy and the assimilated zonal and meridional winds are as large as 3.1 m s−1, which is comparable to the size of the means themselves. The zonal and meridional daily wind correlations range between 0.66 and 0.17. The wind field agreement was actually better among the different systems than between any system and the buoys. However, the agreement among the analysis products was usually better for the zonal winds than for the meridional winds. For the time period and locations presented, the comparisons with the independent data show that no assimilation system is clearly superior to any of the others.

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