scholarly journals The Dynamics of Vortex Rossby Waves and Secondary Eyewall Development in Hurricane Matthew (2016): New Insights from Radar Measurements

2020 ◽  
Vol 77 (7) ◽  
pp. 2349-2374 ◽  
Author(s):  
Stephen R. Guimond ◽  
Paul D. Reasor ◽  
Gerald M. Heymsfield ◽  
Matthew M. McLinden
Keyword(s):  
Angular Momentum ◽  
Large Scale ◽  
Rossby Waves ◽  
Inner Core ◽  
Small Scale ◽  
Wave Kinematics ◽  
Secondary Eyewall Formation ◽  
Radial Flux ◽  
Momentum Budget ◽  
Radar Measurements

AbstractThe structure of vortex Rossby waves (VRWs) and their role in the development of a secondary eyewall in Hurricane Matthew (2016) is examined from observations taken during the NOAA Sensing Hazards with Operational Unmanned Technology (SHOUT) field experiment. Radar measurements from ground-based and airborne systems, with a focus on the NASA High-Altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) instrument on the Global Hawk aircraft, revealed the presence of ~12–15-km-wavelength spiral bands breaking from the inner-core eyewall in the downshear-right quadrant. The vorticity characteristics and calculations of the intrinsic phase speeds of the bands are shown to be consistent with sheared VRWs. A new angular momentum budget methodology is presented that allows an understanding of the secondary eyewall development process with narrow-swath radar measurements. Filtering of the governing equations enables explicit insight into the nonlinear dynamics of scale interactions and the role of the VRWs in the storm structure change. The results indicate that the large-scale (scales > 15 km) vertical flux convergence of angular momentum associated with the VRWs dominates the time tendency with smaller effects from the radial flux term. The small-scale (scales ≤ 15 km) vertical term produces weak, but nonnegligible nonlinear forcing of the large scales primarily through the Reynolds and cross-stress components. The projection of the wave kinematics onto the low-wavenumber (0 and 1) fields appears to be the more significant dynamic process. Flight-level observations show secondary peaks in tangential winds in the radial region where the VRW forcing signatures are active, connecting them with the secondary eyewall formation process.

scholarly journals Circum-nuclear molecular disks: Role in AGN fueling and feedback

2019 ◽  
Vol 15 (S359) ◽  
pp. 312-317
Author(s):  
Francoise Combes
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
High Resolution ◽  
Large Scale ◽  
Active Galaxy ◽  
Small Scale ◽  
Massive Black Hole ◽  
Molecular Outflows ◽  
Molecular Outflow

AbstractGas fueling AGN (Active Galaxy Nuclei) is now traceable at high-resolution with ALMA (Atacama Large Millimeter Array) and NOEMA (NOrthern Extended Millimeter Array). Dynamical mechanisms are essential to exchange angular momentum and drive the gas to the super-massive black hole. While at 100pc scale, the gas is sometimes stalled in nuclear rings, recent observations reaching 10pc scale (50mas), may bring smoking gun evidence of fueling, within a randomly oriented nuclear gas disk. AGN feedback is also observed, in the form of narrow and collimated molecular outflows, which point towards the radio mode, or entrainment by a radio jet. Precession has been observed in a molecular outflow, indicating the precession of the radio jet. One of the best candidates for precession is the Bardeen-Petterson effect at small scale, which exerts a torque on the accreting material, and produces an extended disk warp. The misalignment between the inner and large-scale disk, enhances the coupling of the AGN feedback, since the jet sweeps a large part of the molecular disk.

scholarly journals Magnetic and velocity fields in a dynamo operating at extremely small Ekman and magnetic Prandtl numbers

2017 ◽  
Vol 47 (4) ◽  
pp. 261-276
Author(s):  
Ján Šimkanin ◽  
Juraj Kyselica
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Inner Core ◽  
Strong Field ◽  
Boussinesq Approximation ◽  
Velocity Fields ◽  
Small Scale ◽  
Prandtl Numbers ◽  
Core Rotation ◽  
Inner Core Rotation

AbstractNumerical simulations of the geodynamo are becoming more realistic because of advances in computer technology. Here, the geodynamo model is investigated numerically at the extremely low Ekman and magnetic Prandtl numbers using the PARODY dynamo code. These parameters are more realistic than those used in previous numerical studies of the geodynamo. Our model is based on the Boussinesq approximation and the temperature gradient between upper and lower boundaries is a source of convection. This study attempts to answer the question how realistic the geodynamo models are. Numerical results show that our dynamo belongs to the strong-field dynamos. The generated magnetic field is dipolar and large-scale while convection is small-scale and sheet-like flows (plumes) are preferred to a columnar convection. Scales of magnetic and velocity fields are separated, which enables hydromagnetic dynamos to maintain the magnetic field at the low magnetic Prandtl numbers. The inner core rotation rate is lower than that in previous geodynamo models. On the other hand, dimensional magnitudes of velocity and magnetic fields and those of the magnetic and viscous dissipation are larger than those expected in the Earth’s core due to our parameter range chosen.

Rossby-wave driven zonal flows in the ionospheric E-layer

2007 ◽  
Vol 73 (1) ◽  
pp. 131-140 ◽  
Author(s):  
T. D. KALADZE ◽  
D. J. WU ◽  
O. A. POKHOTELOV ◽  
R. Z. SAGDEEV ◽  
L. STENFLO ◽  
...  
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Maximum Growth ◽  
Present Theory ◽  
Finite Amplitude ◽  
Maximum Growth Rate ◽  
Small Scale ◽  
Reynolds Stresses ◽  
Zonal Flows ◽  
Coupled Equations

Abstract.A novel mechanism for the generation of large-scale zonal flows by small-scale Rossby waves in the Earth's ionospheric E-layer is considered. The generation mechanism is based on the parametric excitation of convective cells by finite amplitude magnetized Rossby waves. To describe this process a generalized Charney equation containing both vector and scalar (Korteweg–de Vries type) nonlinearities is used. The magnetized Rossby waves are supposed to have arbitrary wavelengths (as compared with the Rossby radius). A set of coupled equations describing the nonlinear interaction of magnetized Rossby waves and zonal flows is obtained. The generation of zonal flows is due to the Reynolds stresses produced by finite amplitude magnetized Rossby waves. It is found that the wave vector of the fastest growing mode is perpendicular to that of the magnetized Rossby pump wave. Explicit expression for the maximum growth rate as well as for the optimal spatial dimensions of the zonal flows are obtained. A comparison with existing results is carried out. The present theory can be used for the interpretation of the observations of Rossby-type waves in the Earth's ionosphere.

The Central Barrier, Asymmetry and Random Phase in Chaotic Transport and Mixing by Rossby Waves in a Jet

1998 ◽  
Vol 08 (06) ◽  
pp. 1131-1152 ◽  
Author(s):  
Huijun Yang
Keyword(s):  
Large Scale ◽  
Rossby Waves ◽  
Random Phase ◽  
Kinematic Model ◽  
Global Bifurcation ◽  
Heteroclinic Orbit ◽  
Phase Speed ◽  
Small Scale ◽  
Transport And Mixing ◽  
Geophysical Flow

The central barrier, asymmetry and random perturbation in transport and mixing by Rossby waves in a jet were investigated by simple kinematic model. Two complementary methods were used: A high-resolution Lagrangian Field Advection Model (FAM) and a finite-time Lyapunov exponent analysis. The present study revealed the following: (1) A central barrier can be formed in two Rossby waves without shear flow as well as in a jet, (2) the central barrier may occur in the region with maximum jet speed relative to the phase speed of the traveling wave, whereas the chaotic mixing most likely occurs near the critical lines; the central barrier widens as the phase speed of traveling waves relative to the jet speed increases, (3) asymmetry of wave-breaking is directly related to asymmetry of the critical line location in a jet, (4) the central barrier survives small random perturbations, (5) global bifurcation from a homoclinic orbit to a heteroclinic orbit and global chaos are two main mechanisms for the central barrier destruction. The results suggest that the small scale motions and random processes may not significantly affect the major character of Lagrangian transport and mixing by large-scale geophysical flow. Also potential vorticity mixing provides a unique kinematic and dynamic view of many features of the geophysical flow.

Demonstration of balance-based space averaging and modelling in view of blading—diffuser interaction

2003 ◽  
Vol 217 (4) ◽  
pp. 461-469 ◽  
Author(s):  
F Kreitmeier ◽  
P Lücking
Keyword(s):  
Fluid Dynamics ◽  
Angular Momentum ◽  
Large Scale ◽  
Control Volume ◽  
Three Dimensional ◽  
General Concept ◽  
Control Surface ◽  
Small Scale ◽  
Time Averaging ◽  
One Dimensional

Advanced experimental and numerical methods in the field of fluid dynamics and turbomachinery are increasingly successful in describing real flowfields, i.e. fields that are generally three-dimensional and unsteady. For many purposes, e.g. flow characterization, it is necessary to reduce these flowfields step by step to three-, two- or one-dimensional large-scale unsteady flowfields. This procedure permits a lower-level simulation of the flowfields. However, many averaging approaches are arbitrary or succeed in balancing the flowfields in only a few physical aspects. The first author has already shown the steps of a balance-based procedure that avoids this limitation. Small-scale time averaging of (probabilistically) turbulent inhomogeneities by means of irreversible and reversible small-scale time averaging processes on a threefold infinitesimal control volume element has already been demonstrated. The present paper demonstrates the balance-based procedure of space averaging. It is carried out by averaging generally three-dimensional small-scale time-averaged (deterministic) inhomogeneities using irreversible and reversible space averaging processes on onefold infinitesimal and finite control surfaces. The procedure is, similarly to small-scale time averaging, based on conservative and independent non-conservative small-scale time-averaged integral balance equations. The general concept is to represent all the relevant fluxes through the control surface by appropriate average quantities or numbers. The full use of the vector equations for the linear and angular momentum is important. One of the consequences in space averaging is the introduction of a wrench (parallel linear and angular momentum vectors), which is generally used only in mechanics for the reduction of force systems in space. The flowfield inhomogeneity is described on all dimensional levels via the diffusion intensity of the irreversible averaging process, and, only for space averaging, via the distance vector and the parameter of the wrench. A numerical example on different dimensional levels is presented in detail. The procedure also illustrates the basis of a new and more complete two-and one-dimensional large-scale unsteady theory generally in fluid dynamics and especially in turbomachinery.

scholarly journals On the Turbulence in the Protoplanetary Cloud

1958 ◽  
Vol 8 ◽  
pp. 1023-1024
Author(s):  
V. S. Safronov
Keyword(s):  
Angular Momentum ◽  
Large Scale ◽  
Planetary System ◽  
Gravitational Instability ◽  
Small Scale ◽  
The Sun ◽  
Dust Disk ◽  
Present Distribution ◽  
Scale Turbulence ◽  
Short Time

The problem of turbulence in the protoplanetary cloud is of importance for planetary cosmogony. Chaotic macroscopic motions probably existed in the cloud during its formation. Further evolution of the cloud depended to a great extent upon whether these original motions damped in a short time, or turbulence supported by some source of energy existed during planet formation. According to Kuiper and Fessenkov's hypotheses, massive protoplanets formed as a result of gravitational instability and turned into planets after the dissipation of light elements. Large-scale turbulent motions with mean velocities exceeding the thermal velocities of atoms and molecules would prevent, however, gravitational instability in the cloud, even if its mass was of the order of the mass of the sun. According to Edgeworth and to Gurevitch and Lebedinsky the planets grew gradually from small condensations formed in a flattened dust disk with a mass equal to that of the present planetary system. But even small scale turbulent motions would prevent extreme flattening of the disk necessary in this case for gravitational instability. The problem of turbulence is also connected with the problem of present distribution of angular momentum between the sun and planets, as large-scale turbulence produces redistribution of matter and of angular momentum in the cloud.

The correspondence between drag enhancement and vortical structures in turbulent Taylor–Couette flows with polymer additives: a study of curvature dependence

2019 ◽  
Vol 881 ◽  
pp. 602-616 ◽  
Author(s):  
Jiaxing Song ◽  
Hao Teng ◽  
Nansheng Liu ◽  
Hang Ding ◽  
Xi-Yun Lu ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Angular Momentum ◽  
Direct Numerical Simulation ◽  
Large Scale ◽  
Underlying Mechanism ◽  
Vortical Flow ◽  
Small Scale ◽  
Vortical Structures ◽  
Taylor Couette ◽  
Curvature Dependence

We report direct numerical simulation results that clearly elucidate the mechanism that leads to curvature dependence of drag enhancement (DE) in viscoelastic turbulent Taylor–Couette flow. Change in the angular momentum transport and its inherent link to transitions in vortical flow structures have been explored to depict the influence of the curvature of the flow geometry on DE. Specifically, it has been demonstrated that a transition in vortical structures with increasing radius ratio leads to weakening and elimination of the small-scale Görtler vortices and development and better organization (occupying the entire gap) of large-scale Taylor vortices as also evinced by the patterns of angular momentum current. The commensurate change in DE and its underlying mechanism are examined by contributions of convective flux and polymeric stress to the angular momentum current. The present finding paves the way for capturing highly localized elastic turbulence structures in direct numerical simulation by increasing geometry curvature in traditional turbulent curvilinear flows.

Nonlinear interaction of small‐scale Rossby waves with an intense large‐scale zonal flow

1994 ◽  
Vol 6 (3) ◽  
pp. 1158-1167 ◽  
Author(s):  
Dmitrii Yu. Manin ◽  
Sergey V. Nazarenko
Keyword(s):  
Nonlinear Interaction ◽  
Large Scale ◽  
Rossby Waves ◽  
Zonal Flow ◽  
Small Scale

The Effect of Internally Generated Inner-Core Asymmetries on Tropical Cyclone Potential Intensity*

2007 ◽  
Vol 64 (4) ◽  
pp. 1165-1188 ◽  
Author(s):  
Bo Yang ◽  
Yuqing Wang ◽  
Bin Wang
Keyword(s):  
Angular Momentum ◽  
Tropical Cyclone ◽  
Potential Vorticity ◽  
Inner Core ◽  
Potential Temperature ◽  
Convective Heating ◽  
Internal Dynamic ◽  
Budget Analysis ◽  
Momentum Budget ◽  
Cooling Effects

Abstract In a quiescent environment on an f plane, the internal dynamic processes of a tropical cyclone (TC) can generate axially asymmetric circulations (asymmetries) in its inner-core region. The present study investigates how these inner-core asymmetries affect TC intensity. For this purpose, a three-dimensional (3D) TC model and its axisymmetric (2D) version were used. Both have identical model vertical structure and use the same set of parameters and the same initial conditions. The differences between the two model runs are considered to be due to mainly the effects of the TC asymmetries. The results show that the presence of asymmetries in the 3D run reduces the TC final intensity by about 15% compared with the 2D run, suggesting that the TC asymmetry is a limiting factor to the potential intensity (PI). In the 2D run without asymmetries, the convective heating in the eyewall generates an annular tower of high potential vorticity (PV) with relatively low PV in the eye. The eyewall tilts outward with height significantly. Underneath the tilted eyewall the downdrafts induced by evaporation of rain and melting of snow and graupel make the subcloud-layer inflow dry and cool, which lowers the boundary layer equivalent potential temperature (θe), thus increasing the entropy difference between the air and sea in the vicinity of the radius of maximum wind (RMW). The increased air–sea entropy deficit leads to more energy input into TC from the underlying ocean and thus a greater final intensity. On the other hand, in the 3D run, the model-resolved asymmetric eddies, which are characterized by the vortex Rossby waves in the mid-lower troposphere, play important roles in modifying the symmetric structure of the TC. Potential vorticity and θe budgets indicate that significant inward PV mixing from the eyewall into the eye results in a less-tilted eyewall, which in turn limits the drying and cooling effects of downdrafts in the subcloud layer and reduces the air–sea entropy deficit under the eyewall, thereby reducing the TC intensity. The angular momentum budget analysis shows that the asymmetric eddies tend to reduce the strength of the primary circulation in the vicinity of the RMW. This eddy contribution to the azimuthal mean angular momentum budget is larger than the parameterized horizontal diffusion contribution in the 3D run, suggesting an overall diffusive effect of the asymmetric eddies on the symmetric circulation.

scholarly journals The Origin and Distribution of Angular Momentum in Galaxies

2004 ◽  
Vol 220 ◽  
pp. 467-476 ◽  
Author(s):  
Joel R. Primack
Keyword(s):  
Dark Matter ◽  
Angular Momentum ◽  
Momentum Distribution ◽  
Large Scale ◽  
Cold Dark Matter ◽  
Small Scale ◽  
Dark Halo ◽  
Baryonic Matter ◽  
Dark Matter Halos ◽  
Hydrodynamical Simulations

Cold Dark Matter with a large cosmological constant (ACDM) appears to fit large scale structure observations well. of the possible small scale problems, the Central Cusps and Too Many Satellites problems now appear to be at least partly solved, so Angular Momentum has become the most serious remaining CDM problem. There are actually at least two different angular momentum problems: A. Too much transfer of angular momentum to the dark halo to make big disks, and B. Wrong distribution of specific angular momentum to make spiral galaxies, if the baryonic material has the same angular momentum distribution as the dark matter. the angular momentum of dark matter halos, and presumably that of the galaxies they host, appears to arise largely from the orbital angular momentum of the satellites that they accrete. Since the dark and baryonic matter behave very differently in such accretion events, it is possible that the resulting angular momentum distribution of the baryons is different from that of the dark matter, as required to make the sort of galactic disks that are observed. the latest hydrodynamical simulations give some grounds for hope on this score, but much higher resolution simulations are needed.

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