scholarly journals A study of the effect of internal wave induced turublence on small scale temperature structure in shallow water.

1973 ◽  
Author(s):  
Julian Edward. Minard ◽  
Noel E. J. Boston ◽  
Edward Bennett. Thornton
Keyword(s):  
Internal Wave ◽  
Shallow Water ◽  
Small Scale ◽  
Temperature Structure ◽  
Scale Temperature ◽  
Wave Induced

scholarly journals Unpredictability of internal M<sub>2</sub>

2007 ◽  
Vol 4 (2) ◽  
pp. 303-323
Author(s):  
H. van Haren
Keyword(s):  
Internal Wave ◽  
Tidal Energy ◽  
Short Wave ◽  
Small Scale ◽  
Tidal Waves ◽  
North East ◽  
Background Density ◽  
Continental Slopes ◽  
Shelf Sea ◽  
Wave Induced

Abstract. Current observations from a shelf sea, continental slopes and the abyssal North-East Atlantic Ocean are all dominated by the semidiurnal lunar (M2) tide. It is shown that motions at M2 vary at usually large barotropic and coherent baroclinic scales, >50 km horizontally and >0.5 H vertically. H represents the waterdepth. Such M2-scales are observed even close to topography, the potential source of baroclinic, "internal" tidal waves. In contrast, incoherent small-scale, ~10 km horizontally and ~0.1 H vertically, baroclinic motions are dominated around f, the local inertial frequency, and/or near 2Ω≈S2, the semidiurnal solar tidal frequency. Ω represents the Earth's rotational vector. This confirms earlier suggestions that small-scale baroclinic M2-motions generally do not exist in the ocean in any predictable manner, except in beams very near (<10 km horizontally) to their source. As a result, M2-motions are not directly important for generating shear and internal wave induced mixing in the ocean. Indirectly however, they may contribute to ocean mixing if transfer to small-scale motions at f and/or S2 can be proven. Also far from topography, small-scale motions are found at either or both of the latter frequencies. Different suggestions for the scales at these particular frequencies are discussed, ranging from the variability of "background" density gradients and associated divergence and focusing of internal wave rays to the removal of the internal tidal energy by non-linear interactions. It is noted that near f and S2 the short-wave inertio-gravity wave bounds are found in the limit of very weak stratification, which are often observed in small-scale near-homogeneous layers.

Centimeter-scale-resolution airborne temperature measurements in clouds and in marine surface layer during EUREC4A 

2021 ◽  
Author(s):  
Stanisław Król ◽  
Szymon Malinowski ◽  
Wojciech Kumala ◽  
Jakub Nowak ◽  
Robert Grosz ◽  
...  
Keyword(s):  
Surface Layer ◽  
Sampling Rate ◽  
Temperature Measurements ◽  
Small Scale ◽  
Temperature Structure ◽  
Scale Temperature ◽  
Marine Surface Layer ◽  
Marine Surface ◽  
Temperature Records

&lt;p&gt;&lt;span&gt;Characterization of small-scale temperature structure of convective clouds and their environment is crucial to understand turbulent entrainment, mixing and its effect on cloud dynamics and microphysics. A newly constructed ultra-fast thermometer UFT2, developed from the former UFT-M, allowing for temperature measurements in clouds with the resolution better than few centimeters, was deployed on the British Antarctic Survey Twin-Otter research aircraft in the course of the EUREC4A research campaign. The goal was to perform first ever fine-scale temperature characterization of subtropical marine warm cumulus clouds.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;The prototype instrument worked relatively well and allow to collect data from 7 of 17 research flights, including hundreds of cloud penetrations and segments of flights in the marine surface layer. Data, collected with 20 kHz sampling rate, after filtering and averaging allowed to achieve physical resolution of ~3cm at ~60m/s true air speed of the aircraft.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Performance of the UFT-2 sensor and its calibration will be discussed. The discussion will be illustrated with examples of multi-scale temperature records collected in cloud interiors, cloud edges, cloud shells at various altitudes as well as in the marine surface layer ~30 m above the sea level.&lt;/span&gt;&lt;/p&gt;

scholarly journals Numerical Investigation of Solitary Internal Wave-Induced Global Instability in Shallow Water Benthic Boundary Layers

2006 ◽  
Vol 36 (5) ◽  
pp. 784-812 ◽  
Author(s):  
Peter J. Diamessis ◽  
Larry G. Redekopp
Keyword(s):  
Boundary Layer ◽  
Internal Wave ◽  
Shallow Water ◽  
Water Column ◽  
Separation Bubble ◽  
Vertical Direction ◽  
Finite Difference Schemes ◽  
Global Instability ◽  
Solitary Internal Wave ◽  
Wave Induced

Abstract The time-dependent boundary layer induced by a weakly nonlinear solitary internal wave in shallow water is examined through direct numerical simulation. Waves of depression and elevation are both considered. The mean density field corresponds to that typical of the coastal ocean and lakes where the lower fraction of the water column is subject to the stabilizing effect of a diffuse stratification. Sufficient resolution of the “inviscid” dynamics of the boundary layer is ensured through use of a Legendre spectral multidomain discretization scheme in the vertical direction. At higher Reynolds numbers, where the simulations become underresolved, because of restrictions in available computational resources, spectral accuracy and numerical stability at the scales of physical interest are preserved through use of a penalty scheme in the vertical and explicit spectral filtering. Thus, a highly accurate description of the qualitative dynamics of the wave-induced global instability is possible and finescale physical mechanisms critical to the appearance of this instability are not smeared out by the high artificial dissipation inherent in lower-order finite-difference schemes. Results indicate that, for a wave amplitude exceeding a critical value, the global instability occurs in regions near the bottom boundary where the wave induces an adverse pressure gradient. The structure of the associated separation bubble is modified through the establishment of coherent and synchronous dynamics, characterized by elevated levels of bottom shear stress and a periodic shedding of coherent vortex structures. Although details of the vortex shedding depend on the particular wave forcing involved, these vortical structures always ascend high into the water column. All findings suggest that this global instability is a potent mechanism for benthic turbulence, mixing, and possible sediment resuspension in shallow waters, presumably even more intense than the nominal turbulent boundary layer.

scholarly journals Unpredictability of internal M<sub>2</sub>

Ocean Science ◽  
2007 ◽  
Vol 3 (2) ◽  
pp. 337-344 ◽  
Author(s):  
H. van Haren
Keyword(s):  
Internal Wave ◽  
Tidal Energy ◽  
Short Wave ◽  
Small Scale ◽  
Tidal Waves ◽  
North East ◽  
Background Density ◽  
Continental Slopes ◽  
Shelf Sea ◽  
Wave Induced

Abstract. Current observations from a shelf sea, continental slopes and the abyssal North-East Atlantic Ocean are all dominated by the semidiurnal lunar (M2) tide. It is shown that motions at M2 vary at usually large barotropic and coherent baroclinic scales, >50 km horizontally and >0.5 H vertically. H represents the waterdepth. Such M2-scales are observed even close to topography, the potential source of baroclinic, "internal" tidal waves. In contrast, incoherent small-scale, ~10 km horizontally and ~0.1 H vertically, baroclinic motions are dominated around f, the local inertial frequency, and/or near 2Ω≈S2, the semidiurnal solar tidal frequency. Ω represents the Earth's rotational vector. This confirms earlier suggestions that small-scale baroclinic M2-motions generally do not exist in the ocean in any predictable manner, except in beams very near, <10 km horizontally, to their source. As a result, M2-motions are not directly important for generating shear and internal wave induced mixing. Indirectly however, they may contribute to ocean mixing if transfer to small-scale motions at f and/or S2 and at high internal wave frequencies can be proven. Also far from topography, small-scale motions are found at either one or both of the latter frequencies. Different suggestions for the scales at these particular frequencies are discussed, ranging from the variability of "background" density gradients and associated divergence and focusing of internal wave rays to the removal of the internal tidal energy by non-linear interactions. Near f and S2 particular short-wave inertio-gravity wave bounds are found in the limits of strong and very weak stratification, which are often observed in small-scale layers.

scholarly journals 3–D Models of Galaxy Magnetic Fields with Spiral Shocks

1990 ◽  
Vol 140 ◽  
pp. 133-134
Author(s):  
J. Panesar ◽  
A.H. Nelson
Keyword(s):  
Gas Flow ◽  
Density Wave ◽  
Shock Velocity ◽  
Small Scale ◽  
Hydrodynamic Simulation ◽  
Dynamo Equation ◽  
Scale Turbulence ◽  
Wave Induced ◽  
The Magnetic Field ◽  
Stellar Density

We report here some preliminary results of 3–D numerical simulations of an α–ω dynamo in galaxies with differential rotation, small–scale turbulence, and a shock wave induced by a stellar density wave. We obtain the magnetic field from the standard dynamo equation, but include the spiral shock velocity field from a hydrodynamic simulation of the gas flow in a gravitational field with a spiral perturbation (Johns and Nelson, 1986).

Diffusion Experiments with a Global Discontinuous Galerkin Shallow-Water Model

2009 ◽  
Vol 137 (10) ◽  
pp. 3339-3350 ◽  
Author(s):  
Ramachandran D. Nair
Keyword(s):  
Shallow Water ◽  
Discontinuous Galerkin ◽  
Water Model ◽  
Order System ◽  
Small Scale ◽  
Shallow Water Model ◽  
First Order ◽  
Advection Diffusion Equation ◽  
Diffusion Scheme ◽  
Cubed Sphere

Abstract A second-order diffusion scheme is developed for the discontinuous Galerkin (DG) global shallow-water model. The shallow-water equations are discretized on the cubed sphere tiled with quadrilateral elements relying on a nonorthogonal curvilinear coordinate system. In the viscous shallow-water model the diffusion terms (viscous fluxes) are approximated with two different approaches: 1) the element-wise localized discretization without considering the interelement contributions and 2) the discretization based on the local discontinuous Galerkin (LDG) method. In the LDG formulation the advection–diffusion equation is solved as a first-order system. All of the curvature terms resulting from the cubed-sphere geometry are incorporated into the first-order system. The effectiveness of each diffusion scheme is studied using the standard shallow-water test cases. The approach of element-wise localized discretization of the diffusion term is easy to implement but found to be less effective, and with relatively high diffusion coefficients, it can adversely affect the solution. The shallow-water tests show that the LDG scheme converges monotonically and that the rate of convergence is dependent on the coefficient of diffusion. Also the LDG scheme successfully eliminates small-scale noise, and the simulated results are smooth and comparable to the reference solution.

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