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Comparison of Thermal Variance Dissipation Rates from Moored and Profiling Instruments at the Equator

ScholarsArchive at Oregon State University

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Title Comparison of Thermal Variance Dissipation Rates from Moored and Profiling Instruments at the Equator
Names Perlin, A. (creator)
Moum, J. N. (creator)
Date Issued 2012-09 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by American Meteorological Society and can be found at: http://journals.ametsoc.org/loi/atot.
Abstract As a quantitative test of moored mixing measurements using [subscript χ]pods, a comparison experiment was conducted at 0°, 140°W in October–November 2008. The following three measurement elements were involved: (i) NOAA’s Tropical Atmosphere Ocean (TAO) mooring with five [subscript χ]pods, (ii) a similar mooring 9 km away with seven [subscript χ]pods, and (iii) Chameleon turbulence profiles at an intermediate location.

Dissipation rates of temperature variance and turbulent kinetic energy are compared. In all but 3 of 17 direct comparisons 15-day mean values of [subscript χT] agreed within 95% bootstrap confidence limits computed with the conservative assumption that individual 1-min [subscript χ]pod averages and individual Chameleon profiles are independent. However, significant mean differences occur on 2-day averages. Averaging in time reduces the range (95%) in the observed differences at two locations from a factor of 17 at 1-day averaging time to less than a factor of 2 at 15 days, presumably reflecting the natural variability in both the turbulence and the small-scale fluid dynamics that lead to instability and turbulence.

The motion of [subscript χ]pod on a mooring beneath a surface buoy is complex and requires a complete motion package to define in detail. However, perfect knowledge of the motion of the sensor tip is not necessary to obtain a reasonable measure of [subscript χT]. A sampling test indicated that the most important motion sensor is a pressure sensor sampled rapidly enough to resolve the surface wave–induced motion.
Genre Article
Topic Turbulence
Identifier Perlin, A., J. N. Moum, 2012: Comparison of Thermal Variance Dissipation Rates from Moored and Profiling Instruments at the Equator. Journal of Atmospheric and Oceanic Technology, 29, 1347–1362. doi: http://dx.doi.org/10.1175/JTECH-D-12-00019.1

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