scholarly journals Temperature Microstructure beneath Surface Gravity Waves

2004 ◽  
Vol 21 (11) ◽  
pp. 1747-1757 ◽  
Author(s):  
Craig L. Stevens ◽  
Murray J. Smith
Keyword(s):  
Energy Dissipation ◽  
Structure Function ◽  
Gravity Waves ◽  
Dissipation Rate ◽  
Water Surface ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Surface Gravity ◽  
Reliable Estimate ◽  
Surface Gravity Waves

Abstract Oceanic turbulence very near the water surface controls heat, momentum, energy, and mass transfer at the air–sea interface. This study examines the use of a rising temperature microstructure profiler for determination of the rate of turbulent energy dissipation ε beneath a water surface dominated by wind-driven surface gravity waves. Under short-fetch wind waves there is sufficient turbulent energy to generate an inertial-convective subrange. Thus, as well as the conventional Batchelor spectrum fitting approach, ε can be estimated using the temperature spectrum at lower wavenumbers. The inertial-convective subrange-derived turbulent energy dissipation rate εi compares well with the Batchelor spectrum method εb for higher dissipation rates. Sensor limitations mean that these estimates will be a lower bound. The highest dissipation rate estimates were in the uppermost data bin, indicating the importance of resolving right to the surface. Velocimeter results show that the surface waves modulate the rise velocity of the profiler, with variations reaching 75% of the deep water profiler speed. This increases the uncertainty in the transformation of spectra from frequency to wavenumber space using Taylor's frozen-field hypothesis. The use of an inertial convective structure-function-derived energy dissipation rate avoids this transformation. However, the structure function results are not encouraging as they provide a very poor estimate due to the sensitivity of the calculations and the low signal-to-noise ratio in the data. Repeated profiling illustrates the variability of turbulence intensity near the surface and also enables a reliable estimate of the background temperature gradient to be derived. This provides an improved estimate of vertical diffusion of heat.

scholarly journals Tidal signatures in mesospheric turbulence

2006 ◽  
Vol 24 (2) ◽  
pp. 453-465 ◽  
Author(s):  
C. M. Hall ◽  
S. Nozawa ◽  
A. H. Manson ◽  
C. E. Meek
Keyword(s):  
Energy Dissipation ◽  
Gravity Waves ◽  
High Latitude ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Propagation Direction ◽  
Semidiurnal Tide ◽  
Medium Frequency ◽  
Semidiurnal Variation

Abstract. We search for the presence of tidal signatures in high latitude mesospheric turbulence as parameterized by turbulent energy dissipation rate estimated using a medium frequency radar, quantifying our findings with the aid of correlation analyses. A diurnal periodicity is not particularly evident during the winter and spring months but is a striking feature of the summer mesopause. While semidiurnal variation is present to some degree all year round, it is particularly pronounced in winter. We find that the maximum in the summer 24-h variation corresponds to that of the westward phase of the diurnal tide, and that the maximum in the winter 12 h variation corresponds to that of the southward phase of the semidiurnal tide. This information is used to infer the horizontal propagation direction of gravity waves: during the summer the eastward direction is consistent with closure of the summer vortex, while in winter the inferred directions require more complex arguments.

The evolution of turbulent bursts: the b—ε model

1994 ◽  
Vol 5 (4) ◽  
pp. 537-557 ◽  
Author(s):  
M. Bertsch ◽  
R. Dal Passo ◽  
R. Kersner
Keyword(s):  
Partial Differential Equations ◽  
Energy Dissipation ◽  
Energy Density ◽  
Differential Equations ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Self Similar ◽  
Similar Solutions ◽  
Semi Empirical

We study the semi-empirical b—ε model which describes the time evolution of turbulent spots in the case of equal diffusivity of the turbulent energy density b and the energy dissipation rate ε. We prove that the system of two partial differential equations possesses a solution, and that after some time this solution exhibits self-similar behaviour, provided that the system has self-similar solutions. The existence of such self-similar solutions depends upon the value of a parameter of the model.

scholarly journals The formation of strip-like vortex motion by surface gravity waves

2021 ◽  
Vol 2056 (1) ◽  
pp. 012033
Author(s):  
A V Poplevin ◽  
S V Filatov ◽  
A A Levchenko
Keyword(s):  
Gravity Waves ◽  
Wave Vector ◽  
Water Surface ◽  
Vortex Flow ◽  
Vortex Motion ◽  
Surface Contamination ◽  
Surface Gravity ◽  
Surface Gravity Waves ◽  
Measured Dependence ◽  
Effect Of Surface

Abstract We studied experimentally the generation of vortex flow by non-collinear gravity waves with a frequency of 2.34 Hz. The vortices formed on the water surface have the form of stripes, the width L=π/(2k sin θ) of which is determined by the wave vector k and the angle between them, and the length is determined by the size of the system. We demonstrate that the measured dependence Ω(t) can be described within the recently developed model that considers the Eulerian contribution to the generated vortex flow and the effect of surface contamination.

Surface Gravity Waves

2017 ◽  
Author(s):  
John A. Adam
Keyword(s):  
Gravity Waves ◽  
Water Waves ◽  
Water Surface ◽  
Wave Pattern ◽  
The Body ◽  
Surface Gravity ◽  
Shallow Water Waves ◽  
Ship Waves ◽  
Surface Gravity Waves ◽  
Basic Fluid

This chapter deals with the underlying mathematics of surface gravity waves, defined as gravity waves observed on an air–sea interface of the ocean. Surface gravity waves, or surface waves, differ from internal waves, gravity waves that occur within the body of the water (such as between parts of different densities). Examples of gravity waves are wind-generated waves on the water surface, as well tsunamis and ocean tides. Wind-generated gravity waves on the free surface of the Earth's seas, oceans, ponds, and lakes have a period of between 0.3 and 30 seconds. The chapter first describes the basic fluid equations before discussing the dispersion relations, with a particular focus on deep water waves, shallow water waves, and wavepackets. It also considers ship waves and how dispersion affects the wave pattern produced by a moving object, along with long and short waves.

Inertial-Convective Subrange Estimates of Thermal Variance Dissipation Rate from Moored Temperature Measurements

2010 ◽  
Vol 27 (11) ◽  
pp. 1950-1959 ◽  
Author(s):  
Yanwei Zhang ◽  
James N. Moum
Keyword(s):  
Temperature Gradient ◽  
Gravity Waves ◽  
Dissipation Rate ◽  
Vertical Motion ◽  
Unknown Origin ◽  
Surface Gravity ◽  
Measured Signal ◽  
Vertical Temperature ◽  
Surface Gravity Waves ◽  
Wave Induced

Abstract A procedure for estimating thermal variance dissipation rate χT by scaling the inertial-convective subrange of temperature gradient spectra from thermistor measurements on a Tropical Atmosphere Ocean (TAO) equatorial mooring, maintained by NOAA’s National Data Buoy Center, is demonstrated. The inertial-convective subrange of wavenumbers/frequencies is contaminated by the vertical motion induced by the pumping of the surface float by surface gravity waves through the local vertical temperature gradient. The uncontaminated signal can be retrieved by removing the part of the measured signal that is coherent with the signal induced by surface gravity waves, which must be measured independently. An estimate of χT is then obtained by fitting corrected spectra to theoretical temperature gradient spectra over the inertial-convective subrange (0.05 < f < 0.5 Hz); this estimate is referred to as χTIC. Here χTIC was calculated over 120-min intervals and compared with estimates of χTo determined by scaling temperature gradient spectra at high wavenumbers (viscous-convective and viscous-diffusive subranges). Large differences up to a factor of 20 and of unknown origin occur infrequently, especially when both background currents and vertical temperature gradients are weak, but the results herein indicate that 75% of the data pairs are within a factor of 3 of each other. Tests on 15-, 30-, 60-, 120-min intervals demonstrate that differences between the two methods are nearly random, unbiased, and less than estimates of natural variability determined from unrelated experiments at the same location. Because the inertial-convective subrange occupies a lower-frequency range than is typically used for turbulence measurements, the potential for more routine measurements of χT exists. The evaluation of degraded signals (resampled from original measurements) indicates that a particularly important component of such a measurement is the independent resolution of the surface wave–induced signal.

Turbulent energy dissipation rate measurements by coherent lidar

1995 ◽  
Author(s):  
Viktor A. Banakh ◽  
Natalia N. Kerkis ◽  
Igor N. Smalikho ◽  
Friedrich Koepp ◽  
Christian Werner
Keyword(s):  
Energy Dissipation ◽  
Dissipation Rate ◽  
Turbulent Energy ◽  
Energy Dissipation Rate ◽  
Turbulent Energy Dissipation Rate ◽  
Coherent Lidar
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