• Doron, P., , Bertolucci L. , , Katz J. , , and Osborn T. R. , 2001: Turbulence characteristics and dissipation estimates in the coastal ocean bottom boundary layer from PIV data. J. Phys. Oceanogr., 31, 21082134.

    • Search Google Scholar
    • Export Citation
  • Gregg, M. C., , Peters H. , , Wesson J. C. , , Oakey N. S. , , and Shay T. J. , 1985: Intensive measurements of turbulence and shear in the Equatorial Undercurrent. Nature, 318, 140144.

    • Search Google Scholar
    • Export Citation
  • Lien, R., , Caldwell D. R. , , Gregg M. C. , , and Moum J. N. , 1995: Turbulence variability at the equator in the central Pacific at the beginning of the 1991-1993 El Niño. J. Geophys. Res., 100 (C4), 68816898.

    • Search Google Scholar
    • Export Citation
  • Lien, R., , D’Asaro E. , , and McPhaden M. , 2002: Internal waves and turbulence in the upper central equatorial Pacific: Lagrangian and Eulerian observations. J. Phys. Oceanogr., 32, 26192639.

    • Search Google Scholar
    • Export Citation
  • Lorke, A., , and Wuest A. , 2005: Application of coherent ADCP for turbulence measurements on the bottom boundary layer. J. Atmos. Oceanic Technol., 22, 18211828.

    • Search Google Scholar
    • Export Citation
  • Lueck, R. G., , Huang D. , , Newman D. , , and Box J. , 1997: Turbulence measurement with a moored instrument. J. Atmos. Oceanic Technol., 14, 143161.

    • Search Google Scholar
    • Export Citation
  • McPhee, M. G., 1992: Turbulence heat flux in the upper ocean under sea ice. J. Geophys. Res., 97 (C4), 53655379.

  • Moum, J. N., , and Caldwell D. R. , 1985: Local influences on shear flow turbulence in the equatorial ocean. Science, 230, 215315.

  • Moum, J. N., , and Nash J. D. , 2009: Mixing measurements on an equatorial ocean mooring. J. Atmos. Oceanic Technol., 26, 317336.

  • Moum, J. N., , Gregg M. C. , , Lien R. C. , , and Carr M. , 1995: Comparison of turbulence kinetic energy dissipation rate estimates from two ocean microstructure profilers. J. Atmos. Oceanic Technol., 12, 346366.

    • Search Google Scholar
    • Export Citation
  • Moum, J. N., , Klymak J. M. , , Nash J. D. , , Perlin A. , , and Smyth W. D. , 2007: Energy transport by nonlinear internal waves. J. Phys. Oceanogr., 37, 19681988.

    • Search Google Scholar
    • Export Citation
  • Moum, J. N., , Lien R.-C. , , Perlin A. , , Nash J. D. , , Gregg M. C. , , and Wiles P. J. , 2009: Sea surface cooling at the equator by subsurface mixing in tropical instability waves. Nat. Geosci., 2, 761765, doi:10.1038/NGEO657.

    • Search Google Scholar
    • Export Citation
  • Moum, J. N., , Nash J. D. , , and Smyth W. D. , 2011: Narrowband high-frequency oscillations at the equator. Part I: Interpretation as shear instabilities. J. Phys. Oceanogr., 41, 397411.

    • Search Google Scholar
    • Export Citation
  • Nash, J. D., , and Moum J. N. , 1999: Estimating salinity variance dissipation rate from microstructure conductivity measurements. J. Atmos. Oceanic Technol., 16, 263274.

    • Search Google Scholar
    • Export Citation
  • Osborn, T. R., 1980: Estimates of the local rate of vertical diffusion from dissipation measurements. J. Phys. Oceanogr., 10, 8389.

  • Osborn, T. R., , and Cox C. S. , 1972: Oceanic fine structure. Geophys. Fluid Dyn., 3, 321345.

  • Pamadi, B. N., 2004: Performance, Stability, Dynamics, and Control of Airplanes. AIAA, 780 pp.

  • Sun, C., , Smyth W. D. , , and Moum J. N. , 1998: Dynamic instability of stratified shear flow in the upper equatorial ocean. J. Geophys. Res., 103 (C5), 10 32310 337.

    • Search Google Scholar
    • Export Citation
  • Walchko, K. J., 2002: Low cost inertial navigation: Learning to integrate noise and find your way. M.S. thesis, Dept. of Electrical and Computer Engineering, University of Florida, 80 pp. [Available online at http://www.mil.ufl.edu/publications/thes_diss/Kevin_Walchko_thesis.pdf.]

  • Wiles, P. J., , Rippeth T. P. , , Simpson J. H. , , and Hendricks P. J. , 2006: A novel technique for measuring the rate of turbulence dissipation in the marine environment. Geophys. Res. Let., 33, L21608, doi:10.1029/2006GL027050.

    • Search Google Scholar
    • Export Citation
  • Williams, A. J., , Tochko J. S. , , Koehler R. L. , , Gross T. F. , , Grant W. D. , , and Dunn C. V. R. , 1987: Measurement of turbulence with an acoustic current meter array in the oceanic bottom boundary layer. J. Atmos. Oceanic Technol., 4, 312327.

    • Search Google Scholar
    • Export Citation
  • Zhang, Y., , and Moum J. N. , 2010: Inertial-convective subrange estimates of thermal variance dissipation rate from moored temperature measurements. J. Atmos. Oceanic Technol., 27, 19501959.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 41 41 5
PDF Downloads 29 29 4

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

View More View Less
  • 1 College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon
© Get Permissions
Restricted access

Abstract

As a quantitative test of moored mixing measurements using χpods, 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 χpods, (ii) a similar mooring 9 km away with seven χpods, 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 χT agreed within 95% bootstrap confidence limits computed with the conservative assumption that individual 1-min χpod 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 χpod 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 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.

Corresponding author address: A. Perlin, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331. E-mail: aperlin@coas.oregonstate.edu

Abstract

As a quantitative test of moored mixing measurements using χpods, 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 χpods, (ii) a similar mooring 9 km away with seven χpods, 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 χT agreed within 95% bootstrap confidence limits computed with the conservative assumption that individual 1-min χpod 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 χpod 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 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.

Corresponding author address: A. Perlin, College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331. E-mail: aperlin@coas.oregonstate.edu
Save