Experimental evaluation of the characteristics of vertical mixing in an oceanic thermohalocline on the basis of fine-structure spectra of advection, salt fingers, and small-scale internal waves

1999 ◽  
Vol 10 (2) ◽  
pp. 131-160
Author(s):  
O. I. Efremov ◽  
N. A. Panteleev
Keyword(s):  
Fine Structure ◽  
Internal Waves ◽  
Experimental Evaluation ◽  
Vertical Mixing ◽  
Small Scale ◽  
Salt Fingers

scholarly journals Strong Modulation of Short Wind Waves and Ka-Band Radar Return Due to Internal Waves in the Presence of Surface Films. Theory and Experiment

2021 ◽  
Vol 13 (13) ◽  
pp. 2462
Author(s):  
Stanislav A. Ermakov ◽  
Irina A. Sergievskaya ◽  
Ivan A. Kapustin
Keyword(s):  
Phase Velocity ◽  
Internal Waves ◽  
Wind Waves ◽  
Strong Increase ◽  
Small Scale ◽  
Surface Films ◽  
Ka Band ◽  
Steady Current ◽  
Backscatter Modulation ◽  
Resonance Surface

Strong variability of Ka-band radar backscattering from short wind waves on the surface of water covered with surfactant films in the presence of internal waves (IW) was studied in wave tank experiments. It has been demonstrated that modulation of Ka-band radar return due to IW strongly depends on the relationship between the phase velocity of IW and the velocity of drifting surfactant films. An effect of the strong increase in surfactant concentration was revealed in convergent zones, associated with IW orbital velocities in the presence of a “resonance” surface steady current, the velocity of which was close to the IW phase velocity. A phenomenological model of suppression and modulations in the spectrum of small-scale wind waves due to films and IW was elaborated. It has been shown that backscatter modulation could not be explained by the modulation of free (linear) millimeter-scale Bragg waves, but was associated with the modulation of bound (parasitic) capillary ripples generated by longer, cm–dm-scale waves—a “cascade” modulation mechanism. Theoretical analysis based on the developed model was found to be consistent with experiments. Field observations which qualitatively illustrated the effect of strong modulation of Ka-band radar backscatter due to IW in the presence of resonance drift of surfactant films are presented.

Generation of vertical fine structure in inhomogeneous flow by inertial-gravity internal waves

1993 ◽  
Vol 4 (4) ◽  
pp. 307-315
Author(s):  
A. A. Belobrov ◽  
A. A. Slepyshev ◽  
V. S. Shamov
Keyword(s):  
Fine Structure ◽  
Internal Waves ◽  
Inhomogeneous Flow

scholarly journals Dependence of Model Energy Spectra on Vertical Resolution

2016 ◽  
Vol 144 (4) ◽  
pp. 1407-1421 ◽  
Author(s):  
Michael L. Waite
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Vertical Mixing ◽  
Energy Spectra ◽  
Small Scale ◽  
Rossby Number ◽  
Vertical Resolution ◽  
Wide Range ◽  
Qualitative Shape ◽  
Vertical Grid

Abstract Many high-resolution atmospheric models can reproduce the qualitative shape of the atmospheric kinetic energy spectrum, which has a power-law slope of −3 at large horizontal scales that shallows to approximately −5/3 in the mesoscale. This paper investigates the possible dependence of model energy spectra on the vertical grid resolution. Idealized simulations forced by relaxation to a baroclinically unstable jet are performed for a wide range of vertical grid spacings Δz. Energy spectra are converged for Δz 200 m but are very sensitive to resolution with 500 m ≤ Δz ≤ 2 km. The nature of this sensitivity depends on the vertical mixing scheme. With no vertical mixing or with weak, stability-dependent mixing, the mesoscale spectra are artificially amplified by low resolution: they are shallower and extend to larger scales than in the converged simulations. By contrast, vertical hyperviscosity with fixed grid-scale damping rate has the opposite effect: underresolved spectra are spuriously steepened. High-resolution spectra are converged except for the stability-dependent mixing case, which are damped by excessive mixing due to enhanced shear over a wide range of horizontal scales. It is shown that converged spectra require resolution of all vertical scales associated with the resolved horizontal structures: these include quasigeostrophic scales for large-scale motions with small Rossby number and the buoyancy scale for small-scale motions at large Rossby number. It is speculated that some model energy spectra may be contaminated by low vertical resolution, and it is recommended that vertical-resolution sensitivity tests always be performed.

Magnetic Tube Scale and Electron Acceleration from the Fine Structure of Microwave Bursts

1993 ◽  
Vol 141 ◽  
pp. 279-282
Author(s):  
Huang Guang-Li
Keyword(s):  
Fine Structure ◽  
Single Pulse ◽  
Small Scale ◽  
Short Time Scale ◽  
Magnetic Tube ◽  
Solar Radio Bursts ◽  
Microwave Source ◽  
Tearing Modes ◽  
Cyclotron Maser ◽  
Short Time

AbstractA typical microwave burst with fine structures (type Hand) observed by the Dwingloo multi-channel spectrometer is proposed as evidence of a magnetic tube with a small scale and acceleration of electron beams with a short time scale at the source. It is predicted from the observations and theory that the average velocity of non-thermal electrons is about 0.1c and the density of the beam is about 104 cm−3. There is a micro-magnetic tube with a scale length of six hundred kilometers at the microwave source. There is also a quasi-periodic (~ 20 ms) evolution of the beam energy, which may be accelerated by tearing modes. The spectrum of the burst can be explained by the non-uniformity of the magnetic field. The evolution of the spectrum during a single pulse may result from the electron cyclotron maser instability. Hence, information from the fine structure of the spectrum of solar radio bursts is very important for understanding the mechanism of solar flares.

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