Saturation of the internal tide over the inner continental shelf. Part I: Observations

2021 ◽  
Author(s):  
Johannes Becherer ◽  
James N. Moum ◽  
Joseph Calantoni ◽  
John A. Colosi ◽  
John A. Barth ◽  
...  
Keyword(s):  
Energy Flux ◽  
Dissipation Rate ◽  
Internal Tide ◽  
Shallow Waters ◽  
Turbulence Energy ◽  
Flux Divergence ◽  
Central California ◽  
Turbulence Energy Dissipation ◽  
Wave Energy Flux ◽  
Inner Continental Shelf

AbstractBroadly-distributed measurements of velocity, density and turbulence spanning the inner shelf off central California indicate that (i) the average shoreward-directed internal tide energy flux (〈FE〉) decreases to near 0 at the 25 m isobath; (ii) the vertically-integrated turbulence dissipation rate (〈D〉) is approximately equal to the flux divergence of internal tide energy (∂x〈FE〉); (iii) the ratio of turbulence energy dissipation in the interior relative to the bottom boundary layer (BBL) decreases toward shallow waters; (iv) going inshore, 〈FE〉 becomes decorrelated with the incoming internal wave energy flux; and (v) 〈FE〉 becomes increasingly correlated with stratification toward shallower water.

Saturation of the internal tide over the inner continental shelf. Part II: Parameterization

2021 ◽  
Author(s):  
Johannes Becherer ◽  
James N. Moum ◽  
Joseph Calantoni ◽  
John A. Colosi ◽  
John A. Barth ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Energy Flux ◽  
Gravity Waves ◽  
Water Depth ◽  
Surf Zone ◽  
Internal Tide ◽  
Data Sets ◽  
Flux Divergence ◽  
Surface Gravity Waves ◽  
Inner Continental Shelf

AbstractHere, we develop a framework for understanding the observations presented in the accompanying paper (Part I) by Becherer et al. (2021). In this framework, the internal tide saturates as it shoals due to amplitude limitation with decreasing water depth (H). From this framework evolves estimates of averaged energetics of the internal tide; specifically, energy, 〈APE〉, energy flux, 〈FE〉, and energy flux divergence, ∂x 〈FE〉. Since we observe that 〈D〉 ≈ ∂x 〈FE〉, we also interpret our estimate of ∂x 〈FE〉 as 〈D〉. These estimates represent a parameterization of the energy in the internal tide as it saturates over the inner continental shelf. The parameterization depends solely on depth-mean stratification and bathymetry. A summary result is that the cross-shelf depth dependencies of 〈APE〉, 〈FE〉 and ∂x 〈FE〉 are analogous to those for shoaling surface gravity waves in the surf zone, suggesting that the inner shelf is the surf zone for the internal tide. A test of our simple parameterization against a range of data sets suggests that it is broadly applicable.

Sensitizing the Dissipation Equation to Irrotational Strains

1980 ◽  
Vol 102 (1) ◽  
pp. 34-40 ◽  
Author(s):  
K. Hanjalic´ ◽  
B. E. Launder
Keyword(s):  
Energy Transfer ◽  
Energy Dissipation ◽  
Boundary Layers ◽  
Dissipation Rate ◽  
Energy Dissipation Rate ◽  
Turbulent Boundary Layers ◽  
Turbulence Energy ◽  
Turbulence Energy Dissipation ◽  
Dissipation Equation

The paper recommends the addition of an extra term to the conventional approximate transport equation for the turbulence energy dissipation rate. The term may be interpreted as emphasizing the role of irrotational deformations in promoting energy transfer across the spectrum or, equivalently, of augmenting the influence of normal strains. Calculations, including the new term, are reported for the plane and round jet, and for several turbulent boundary layers. In the cases considered the addition of the new term significantly improves agreement with experiment.

Energy Flux and Dissipation in Luzon Strait: Two Tales of Two Ridges

2011 ◽  
Vol 41 (11) ◽  
pp. 2211-2222 ◽  
Author(s):  
Matthew H. Alford ◽  
Jennifer A. MacKinnon ◽  
Jonathan D. Nash ◽  
Harper Simmons ◽  
Andy Pickering ◽  
...  
Keyword(s):  
Energy Flux ◽  
Spring Tide ◽  
Internal Tide ◽  
Wave Pattern ◽  
The Philippines ◽  
Luzon Strait ◽  
Net Energy ◽  
Energy Fluxes ◽  
Flux Divergence ◽  
Turbulent Dissipation

Abstract Internal tide generation, propagation, and dissipation are investigated in Luzon Strait, a system of two quasi-parallel ridges situated between Taiwan and the Philippines. Two profiling moorings deployed for about 20 days and a set of nineteen 36-h lowered ADCP–CTD time series stations allowed separate measurement of diurnal and semidiurnal internal tide signals. Measurements were concentrated on a northern line, where the ridge spacing was approximately equal to the mode-1 wavelength for semidiurnal motions, and a southern line, where the spacing was approximately two-thirds that. The authors contrast the two sites to emphasize the potential importance of resonance between generation sites. Throughout Luzon Strait, baroclinic energy, energy fluxes, and turbulent dissipation were some of the strongest ever measured. Peak-to-peak baroclinic velocity and vertical displacements often exceeded 2 m s−1 and 300 m, respectively. Energy fluxes exceeding 60 kW m−1 were measured at spring tide at the western end of the southern line. On the northern line, where the western ridge generates appreciable eastward-moving signals, net energy flux between the ridges was much smaller, exhibiting a nearly standing wave pattern. Overturns tens to hundreds of meters high were observed at almost all stations. Associated dissipation was elevated in the bottom 500–1000 m but was strongest by far atop the western ridge on the northern line, where >500-m overturns resulted in dissipation exceeding 2 × 10−6 W kg−1 (implying diapycnal diffusivity Kρ > 0.2 m2 s−1). Integrated dissipation at this location is comparable to conversion and flux divergence terms in the energy budget. The authors speculate that resonance between the two ridges may partly explain the energetic motions and heightened dissipation.

Statistics of Internal Tide Bores and Internal Solitary Waves Observed on the Inner Continental Shelf off Point Sal, California

2018 ◽  
Vol 48 (1) ◽  
pp. 123-143 ◽  
Author(s):  
John A. Colosi ◽  
Nirnimesh Kumar ◽  
Sutara H. Suanda ◽  
Tucker M. Freismuth ◽  
Jamie H. MacMahan
Keyword(s):  
Continental Shelf ◽  
Energy Flux ◽  
Solitary Waves ◽  
Internal Tide ◽  
Propagation Loss ◽  
Internal Solitary Waves ◽  
Time Behavior ◽  
Time Duration ◽  
Match Filter ◽  
Inner Continental Shelf

AbstractMoored observations of temperature and current were collected on the inner continental shelf off Point Sal, California, between 9 June and 8 August 2015. The measurements consist of 10 moorings in total: 4 moorings each on the 50- and 30-m isobaths covering a 10-km along-shelf distance and an across-shelf section of moorings on the 50-, 40-, 30-, and 20-m isobaths covering a 5-km distance. Energetic, highly variable, and strongly dissipating transient wave events termed internal tide bores and internal solitary waves (ISWs) dominate the records. Simple models of the bore and ISW space–time behavior are implemented as a temperature match filter to detect events and estimate wave packet parameters as a function of time and mooring position. Wave-derived quantities include 1) group speed and direction; 2) time of arrival, time duration, vertical displacement amplitude, and waves per day; and 3) energy density, energy flux, and propagation loss. In total, over 1000 bore events and over 9000 ISW events were detected providing well-sampled statistical distributions. Statistics of the waves are rather insensitive to position along shelf but change markedly in the across-shelf direction. Two compelling results are 1) that the probability density functions for bore and ISW energy flux are nearly exponential, suggesting the importance of interference and 2) that wave propagation loss is proportional to energy flux, thus giving an exponential decay of energy flux toward shore with an e-folding scale of 2–2.4 km and average dissipation rates for bores and ISWs of 144 and 1.5 W m−1, respectively.

Sign in / Sign up

Export Citation Format

Share Document