Intermittency of near-bottom turbulence in tidal flow on a shallow shelf
Article first published online: 11 MAY 2010
Copyright 2010 by the American Geophysical Union.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 115, Issue C5, May 2010
How to Cite
2010), Intermittency of near-bottom turbulence in tidal flow on a shallow shelf, J. Geophys. Res., 115, C05006, doi:10.1029/2009JC005325., , , , and (
- Issue published online: 11 MAY 2010
- Article first published online: 11 MAY 2010
- Manuscript Accepted: 20 NOV 2009
- Manuscript Revised: 22 SEP 2009
- Manuscript Received: 12 FEB 2009
 The higher-order structure functions of vertical velocity fluctuations (transverse structure functions (TSF)) were employed to study the characteristics of turbulence intermittency in a reversing tidal flow on a 19 m deep shallow shelf of the East China Sea. Measurements from a downward-looking, bottom-mounted Acoustic Doppler Velocimeter, positioned 0.45 m above the seafloor, which spanned two semidiurnal tidal cycles, were analyzed. A classical lognormal single-parameter (μ) model for intermittency and the universal multifractal approach (specifically, the two-parameter (C1 and α) log-Levy model) were employed to analyze the TSF exponent ξ(q) in tidally driven turbulent boundary layer and to estimate μ, C1, and α. During the energetic flooding tidal phases, the parameters of intermittency models approached the mean values of ≈ 0.24, 1 ≈ 0.15, and ≈ 1.5, which are accepted as the universal values for fully developed turbulence at high Reynolds numbers. With the decrease of advection velocity, μ and C1 increased up to μ ≈ 0.5–0.6 and C1 ≈ 0.25–0.35, but α decreased to about 1.4. The results explain the reported disparities between the smaller “universal” values of intermittency parameters μ and C1 (mostly measured in laboratory and atmospheric high Reynolds number flows) and those (μ = 0.4–0.5) reported for oceanic stratified turbulence in the pycnocline, which is associated with relatively low local Reynolds numbers Rλw. The scaling exponents ξ(2) of the second-order TSF, relative to the third-order structure function, was also found to be a decreasing function of Rλw, approaching the classical value of 2/3 only at very high Rλw. A larger departure from the universal turbulent regime at lower Reynolds numbers could be attributed to the higher anisotropy and associated intermittency of underdeveloped turbulence.