Description of the Perturbations of Oceanic Geostrophic Currents with Linear Vertical Velocity Shear Taking into Account Friction and Diffusion of Density

2019 ◽  
Vol 55 (2) ◽  
pp. 207-217 ◽  
Author(s):  
N. P. Kuzmina ◽  
S. L. Skorokhodov ◽  
N. V. Zhurbas ◽  
D. A. Lyzhkov
Keyword(s):  
Vertical Velocity ◽  
Velocity Shear ◽  
Geostrophic Currents ◽  
And Diffusion

scholarly journals Seasonal Modulation of Eddy Kinetic Energy and Its Formation Mechanism in the Southeast Indian Ocean

2011 ◽  
Vol 41 (4) ◽  
pp. 657-665 ◽  
Author(s):  
Fan Jia ◽  
Lixin Wu ◽  
Bo Qiu
Keyword(s):  
Indian Ocean ◽  
Kinetic Energy ◽  
Vertical Velocity ◽  
Baroclinic Instability ◽  
Mesoscale Eddy ◽  
Eddy Kinetic Energy ◽  
Velocity Shear ◽  
Austral Spring ◽  
Eddy Activity ◽  
South Indian

Abstract Mesoscale eddy activity in the southeast Indian Ocean (15°–30°S, 60°–110°E) is investigated based on available satellite altimetry observations. The observed sea level anomaly data show that this region is the only eastern basin among the global oceans where strong eddy activity exists. Furthermore, the eddy kinetic energy (EKE) level in this region displays a distinct seasonal cycle with the maximum in austral summer and minimum in austral winter. It is found that this seasonal modulation of EKE is mediated by baroclinic instability associated with the surface-intensified South Indian Countercurrent (SICC) and the underlying South Equatorial Current (SEC) system. In austral spring and summer the enhanced flux forcing of combined meridional Ekman and geostrophic convergence strengthens the upper-ocean meridional temperature gradient, intensifying the SICC front and its vertical velocity shear. Modulation of the vertical velocity shear results in the seasonal changes in the strength of baroclinic instability, leading to the seasonal EKE variations in the southeast Indian Ocean.

scholarly journals Subsurface maxima in buoyant fish eggs indicate vertical velocity shear and spatially limited spawning grounds

2018 ◽  
Vol 64 (3) ◽  
pp. 1239-1251 ◽  
Author(s):  
Kjersti Opstad Strand ◽  
Frode Vikebø ◽  
Svein Sundby ◽  
Ann Kristin Sperrevik ◽  
øyvind Breivik
Keyword(s):  
Vertical Velocity ◽  
Velocity Shear ◽  
Fish Eggs ◽  
Spawning Grounds

scholarly journals Description of the perturbations of oceanic geostrophic currents with linear vertical velocity shear taking into account friction and diffusion of density

2019 ◽  
Vol 55 (2) ◽  
pp. 73-85
Author(s):  
N. P. Kuzmina ◽  
S. L. Skorokhodov ◽  
N. V. Zhurbas ◽  
D. A. Lyzhkov
Keyword(s):  
Vertical Velocity ◽  
Maximum Flow ◽  
Arctic Basin ◽  
Stable Stratification ◽  
Short Wave ◽  
Velocity Shear ◽  
The Arctic ◽  
Mesoscale Structures ◽  
Wide Range ◽  
Geostrophic Flows

A spectral problem of Orr-Sommerfeld type for describing stable and unstable disturbances of oceanic geostrophic flows with linear vertical velocity shear is considered. Calculations of eigenvalues, increments of growth rate of unstable modes, and eigenfunctions of the fastest growing disturbances are presented. It is found that the instability of the flow is observed over a wide range of horizontal scales: in addition to long-wave perturbations with a phase velocity exceeding the maximum flow velocity and perturbations with scales of the Rossby radius, short-wave modes with scales much smaller than the Rossby radius (sub-mesoscale structures) exist. The results of the model are used to describe intrusions in the Arctic basin, which are observed under conditions of absolutely stable stratification.

scholarly journals The Kinematics of the Planetary Nebulae in the Large Magellanic Cloud

1989 ◽  
Vol 131 ◽  
pp. 352-352
Author(s):  
Stephen J. Meatheringham ◽  
Michael A. Dopita ◽  
Holland. C. Ford ◽  
B. Louise Webster
Keyword(s):  
Vertical Velocity ◽  
Rotation Curve ◽  
Velocity Dispersion ◽  
Transverse Velocity ◽  
Planetary Nebulae ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Radial Velocities ◽  
Solar Neighbourhood ◽  
And Diffusion

The radial velocities of a total of 94 Planetary Nebulae (PN) in the Large Magellanic Cloud (LMC) have been determined. The kinematics of the population of planetary nebulae is compared with the H I data in the context of a re-analysis of the survey by Rohlfs et al. (1984), taking into account the transverse velocity of the LMC. We find that the best solution for this transverse velocity is 275±65 km s−1, and that the LMC is near perigalacticon. This is consistent with a maximum Galactic mass of order 4.5 × 1011M⊙ out to 51 kpc the rotation curve obtained after correction for this velocity implies a mass of (4.6 × 0.3) × 109 M⊙ within a radius of 3 degrees, or about 6 × 109 M⊙, total. The rotation solution for the PN population is essentially identical with that of the H I, but the vertical velocity dispersion of 19.1 km s−1 is much greater than the value of 5.4 km s−1 found for the H I. This increase in velocity dispersion is consistent with it being the result of orbital heating and diffusion operating in the LMC in a manner essentially identical with that found for the solar neighbourhood.

Meridional Circulation, Turbulence, and Diffusion Processes in Stars

1976 ◽  
Vol 32 ◽  
pp. 109-116 ◽  
Author(s):  
S. Vauclair
Keyword(s):  
Convection Zone ◽  
Diffusion Processes ◽  
Meridional Circulation ◽  
Diffusion Time ◽  
Work In Progress ◽  
First Results ◽  
Stellar Envelopes ◽  
And Diffusion ◽  
Turbulence And Diffusion ◽  
Hr Diagram

This paper gives the first results of a work in progress, in collaboration with G. Michaud and G. Vauclair. It is a first attempt to compute the effects of meridional circulation and turbulence on diffusion processes in stellar envelopes. Computations have been made for a 2 Mʘstar, which lies in the Am - δ Scuti region of the HR diagram.Let us recall that in Am stars diffusion cannot occur between the two outer convection zones, contrary to what was assumed by Watson (1970, 1971) and Smith (1971), since they are linked by overshooting (Latour, 1972; Toomre et al., 1975). But diffusion may occur at the bottom of the second convection zone. According to Vauclair et al. (1974), the second convection zone, due to He II ionization, disappears after a time equal to the helium diffusion time, and then diffusion may happen at the bottom of the first convection zone, so that the arguments by Watson and Smith are preserved.

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