The Absolute Angular Momentum Budget of an Extratropical Cyclone: Quasi-Lagrangian Diagnostics 3

1976 ◽  
Vol 104 (1) ◽  
pp. 3-14 ◽  
Author(s):  
Donald R. Johnson ◽  
William K. Downey
Keyword(s):  
Angular Momentum ◽  
Extratropical Cyclone ◽  
Momentum Budget ◽  
The Absolute

scholarly journals Wave Forcing of Zonal Mean Angular Momentum in Various Coordinate Systems

2014 ◽  
Vol 71 (6) ◽  
pp. 2221-2229
Author(s):  
Joseph Egger ◽  
Klaus-Peter Hoinka
Keyword(s):  
Angular Momentum ◽  
Weighted Averaging ◽  
Coordinate Systems ◽  
Mean Flow ◽  
Flux Divergence ◽  
Standard Case ◽  
Wave Forcing ◽  
Momentum Budget ◽  
Flow Part ◽  
Isentropic Coordinates

Abstract The wave forcing of the atmospheric mean flow in isentropic coordinates has been investigated intensively in the past with the divergence of the Eliassen–Palm flux playing a dominating role. These concepts are reviewed briefly and it is pointed out that angular momentum is attractive in this context because the wave driving can be written in the form of a flux divergence. This helps to evaluate the wave forcing in other coordinate systems with a different separation of waves and mean flow. The following coordinates are chosen: (λ, φ, z), (λ, φ, θ), and (λ, θ, z). To be consistent, only one type of zonal averaging should be used. Mass-weighted averaging is applied in the isentropic standard case and simple averaging is applied in the others. The wave driving is presented for all three systems. It has to balance essentially the mean-flow part of the “Coriolis term” in the angular momentum budget in (φ, z) and (θ, z) coordinates but not in the (φ, θ) system where the form drag is a mean-flow term and, therefore, the forcing pattern differs from what has been published so far.

scholarly journals Lateral chirality-sorting optical forces

2015 ◽  
Vol 112 (43) ◽  
pp. 13190-13194 ◽  
Author(s):  
Amaury Hayat ◽  
J. P. Balthasar Mueller ◽  
Federico Capasso
Keyword(s):  
Wave Propagation ◽  
Angular Momentum ◽  
Field Gradient ◽  
Transverse Component ◽  
Evanescent Waves ◽  
Unusual Property ◽  
Optical Forces ◽  
Spin Angular Momentum ◽  
Absolute Strength ◽  
The Absolute

The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. Because their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces.

scholarly journals Isentropic Pressure and Mountain Torques

2009 ◽  
Vol 137 (9) ◽  
pp. 3047-3054 ◽  
Author(s):  
Joseph Egger ◽  
Klaus-Peter Hoinka
Keyword(s):  
Angular Momentum ◽  
Potential Temperature ◽  
Polar Caps ◽  
The Earth ◽  
Momentum Budget

Abstract The relation of pressure torques and mountain torques is investigated on the basis of observations for the polar caps, two midlatitude and two subtropical belts, and a tropical belt by evaluating the lagged covariances of these torques for various isentropic surfaces. It is only in the polar domains and the northern midlatitude belts that the transfer of angular momentum to and from the earth at the mountains is associated with pressure torques acting in the same sense. The situation is more complicated in all other belts. The covariances decline with increasing potential temperature (height). The role of both torques in the angular momentum budget of a belt is discussed.

scholarly journals Angular momentum budget in General Circulation Models of superrotating atmospheres: A critical diagnostic

2012 ◽  
Vol 117 (E12) ◽  
pp. n/a-n/a ◽  
Author(s):  
Sébastien Lebonnois ◽  
Curt Covey ◽  
Allen Grossman ◽  
Helen Parish ◽  
Gerald Schubert ◽  
...  
Keyword(s):  
Angular Momentum ◽  
General Circulation ◽  
General Circulation Models ◽  
Momentum Budget

scholarly journals Effects of Horizontal Diffusion on Tropical Cyclone Intensity Change and Structure in Idealized Three-Dimensional Numerical Simulations

2015 ◽  
Vol 143 (10) ◽  
pp. 3981-3995 ◽  
Author(s):  
Jun A. Zhang ◽  
Frank D. Marks
Keyword(s):  
Boundary Layer ◽  
Angular Momentum ◽  
Tropical Cyclone ◽  
Three Dimensional ◽  
Horizontal Resolution ◽  
Intensity Change ◽  
Vertical Diffusion ◽  
Layer Height ◽  
Horizontal Diffusion ◽  
Momentum Budget

Abstract This study examines the effects of horizontal diffusion on tropical cyclone (TC) intensity change and structure using idealized simulations of the Hurricane Weather Research and Forecasting Model (HWRF). A series of sensitivity experiments were conducted with varying horizontal mixing lengths (Lh), but kept the vertical diffusion coefficient and other physical parameterizations unchanged. The results show that both simulated maximum intensity and intensity change are sensitive to the Lh used in the parameterization of the horizontal turbulent flux, in particular, for Lh less than the model’s horizontal resolution. The results also show that simulated storm structures such as storm size, kinematic boundary layer height, and eyewall slope are sensitive to Lh as well. However, Lh has little impact on the magnitude of the surface inflow angle and thermodynamic mixed layer height. Angular momentum budget analyses indicate that the effect of Lh is to mainly spin down a TC vortex. Both mean and eddy advection terms in the angular momentum budget are affected by the magnitude of Lh. For smaller Lh, the convergence of angular momentum is larger in the boundary layer, which leads to a faster spinup of the vortex. The resolved eddy advection of angular momentum plays an important role in the spinup of the low-level vortex inward from the radius of the maximum wind speed when Lh is small.

scholarly journals The Hurricane Intensity Issue

2005 ◽  
Vol 133 (7) ◽  
pp. 1886-1912 ◽  
Author(s):  
T. N. Krishnamurti ◽  
S. Pattnaik ◽  
L. Stefanova ◽  
T. S. V. Vijaya Kumar ◽  
B. P. Mackey ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Kinetic Energy ◽  
Potential Energy ◽  
Energy Exchange ◽  
Friction Model ◽  
Cylindrical Coordinates ◽  
Scale Interaction ◽  
Available Potential Energy ◽  
Momentum Budget ◽  
Interaction Approach

Abstract The intensity issue of hurricanes is addressed in this paper using the angular momentum budget of a hurricane in storm-relative cylindrical coordinates and a scale-interaction approach. In the angular momentum budget in storm-relative coordinates, a large outer angular momentum of the hurricane is depleted continually along inflowing trajectories. This depletion occurs via surface and planetary boundary layer friction, model diffusion, and “cloud torques”; the latter is a principal contributor to the diminution of outer angular momentum. The eventual angular momentum of the parcel near the storm center determines the storm’s final intensity. The scale-interaction approach is the familiar energetics in the wavenumber domain where the eddy and zonal kinetic energy on the hurricane scale offer some insights on its intensity. Here, however, these are cast in storm-centered local cylindrical coordinates as a point of reference. The wavenumbers include azimuthally averaged wavenumber 0, principal hurricane-scale asymmetries (wavenumbers 1 and 2, determined from datasets) and other scales. The main questions asked here relate to the role of the individual cloud scales in supplying energy to the scales of the hurricane, thus contributing to its intensity. A principal finding is that cloud scales carry most of their variance, via organized convection, directly on the scales of the hurricane. The generation of available potential energy and the transformation of eddy kinetic energy from the cloud scale are in fact directly passed on to the hurricane scale by the vertical overturning processes on the hurricane scale. Less of the kinetic energy is generated on the scales of individual clouds that are of the order of a few kilometers. The other major components of the energetics are the kinetic-to-kinetic energy exchange and available potential-to-available potential energy exchange among different scales. These occur via triad interaction and were noted to be essentially downscale transfer, that is, a cascading process. It is the balance among these processes that seems to dictate the final intensity.

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