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Abstract Estimates of turbulence kinetic energy (TKE) dissipation rate (ε) are key in understanding how heat, gas, and other climate‐relevant properties are transferred across the air‐sea interface and mixed within the ocean. A relatively new method involving moored pulse‐coherent acoustic Doppler current profilers (ADCPs) allows for estimates ofεwith concurrent surface flux and wave measurements across an extensive length of time and range of conditions. Here, we present 9 months of moored estimates ofεat a fixed depth of 8.4 m at the Stratus mooring site (20°S, 85°W). We find that turbulence regimes are quantified similarly using the Obukhov length scaleand the newer Langmuir stability length scale, suggesting that ocean‐side friction velocityimplicitly captures the influence of Langmuir turbulence at this site. This is illustrated by a strong correlation between surface Stokes driftandthat is likely facilitated by the steady Southeast trade winds regime. In certain regimes,, whereis the von Kármán constant andis instrument depth, and surface buoyancy flux capture our estimates ofwell, collapsing data points near unity. We find that a newer Langmuir turbulence scaling, based onand, scalesεwell at times but is overall less consistent than. Monin‐Obukhov similarity theory (MOST) relationships from prior studies in a variety of aquatic and atmospheric settings largely agree with our data in conditions where convection and wind‐driven current shear are both significant sources of TKE, but diverge in other regimes.
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A Model for Turbulence Spectra in the Equilibrium Range of the Stable Atmospheric Boundary Layer
Abstract Stratification can cause turbulence spectra to deviate from Kolmogorov's isotropicpower law scaling in the universal equilibrium range at high Reynolds numbers. However, a consensus has not been reached with regard to the exact shape of the spectra. Here we propose a shape of the turbulent kinetic energy and temperature spectra in horizontal wavenumber for the equilibrium range that consists of three regimes at small Froude number: the buoyancy subrange, a transition region, and the isotropic inertial subrange through dimensional analysis and substantial revision of previous theoretical approximation. These spectral regimes are confirmed by various observations in the atmospheric boundary layer. The representation of the transition region in direct numerical simulations will require large‐scale separation between the Dougherty‐Ozmidov scale and the Kolmogorov scale for strongly stratified turbulence at high Reynolds numbers, which is still challenging computationally. In addition, we suggest that the failure of Monin‐Obukhov similarity theory in the very stable atmospheric boundary layer is due to the fact that it does not consider the buoyancy scale that characterizes the transition region.
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- Award ID(s):
- 1832170
- PAR ID:
- 10453557
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Volume:
- 125
- Issue:
- 5
- ISSN:
- 2169-897X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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