Group velocity and energy transport by Rossby waves

1978 ◽  
Vol 34 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Akira Masuda
Keyword(s):  
Group Velocity ◽  
Energy Transport ◽  
Rossby Waves

Topographic Rossby Waves in the Abyssal South China Sea

2021 ◽  
Author(s):  
QI QUAN ◽  
ZHONGYA CAI ◽  
GUANGZHEN JIN ◽  
ZHIQIANG LIU
Keyword(s):  
South China Sea ◽  
Group Velocity ◽  
South China ◽  
Large Scale ◽  
Rossby Waves ◽  
Western Boundary ◽  
Horizontal Shear ◽  
Boundary Current ◽  
China Sea ◽  
Topographic Rossby Waves

AbstractTopographic Rossby waves (TRWs) in the abyssal South China Sea (SCS) are investigated using observations and high-resolution numerical simulations. These energetic waves can account for over 40% of the kinetic energy (KE) variability in the deep western boundary current and seamount region in the central SCS. This proportion can even reach 70% over slopes in the northern and southern SCS. The TRW-induced currents exhibit columnar (i.e., in-phase) structure in which the speed increases downward. Wave properties such as the period (5–60 days), wavelength (100–500 km), and vertical trapping scale (102–103 m) vary significantly depending on environmental parameters of the SCS. The TRW energy propagates along steep topography with phase propagation offshore. TRWs with high frequencies exhibit a stronger climbing effect than low-frequency ones and hence can move further upslope. For TRWs with a certain frequency, the wavelength and trapping scale are dominated by the topographic beta, whereas the group velocity is more sensitive to the internal Rossby deformation radius. Background circulation with horizontal shear can change the wavelength and direction of TRWs if the flow velocity is comparable to the group velocity, particularly in the central, southern, and eastern SCS. A case study suggests two possible energy sources for TRWs: mesoscale perturbation in the upper layer and large-scale background circulation in the deep layer. The former provides KE by pressure work, whereas the latter transfers the available potential energy (APE) through baroclinic instability.

scholarly journals Propagation properties of Rossby waves for latitudinal β-plane variations of <I>f</I> and zonal variations of the shallow water speed

2012 ◽  
Vol 30 (5) ◽  
pp. 849-855 ◽  
Author(s):  
C. T. Duba ◽  
J. F. McKenzie
Keyword(s):  
Shallow Water ◽  
Group Velocity ◽  
Rossby Wave ◽  
Rossby Waves ◽  
Low Frequency ◽  
Wave Number ◽  
Coriolis Parameter ◽  
Propagation Properties ◽  
Wave Normal ◽  
Water Speed

Abstract. Using the shallow water equations for a rotating layer of fluid, the wave and dispersion equations for Rossby waves are developed for the cases of both the standard β-plane approximation for the latitudinal variation of the Coriolis parameter f and a zonal variation of the shallow water speed. It is well known that the wave normal diagram for the standard (mid-latitude) Rossby wave on a β-plane is a circle in wave number (ky,kx) space, whose centre is displaced −β/2 ω units along the negative kx axis, and whose radius is less than this displacement, which means that phase propagation is entirely westward. This form of anisotropy (arising from the latitudinal y variation of f), combined with the highly dispersive nature of the wave, gives rise to a group velocity diagram which permits eastward as well as westward propagation. It is shown that the group velocity diagram is an ellipse, whose centre is displaced westward, and whose major and minor axes give the maximum westward, eastward and northward (southward) group speeds as functions of the frequency and a parameter m which measures the ratio of the low frequency-long wavelength Rossby wave speed to the shallow water speed. We believe these properties of group velocity diagram have not been elucidated in this way before. We present a similar derivation of the wave normal diagram and its associated group velocity curve for the case of a zonal (x) variation of the shallow water speed, which may arise when the depth of an ocean varies zonally from a continental shelf.

scholarly journals Acoustic Bloch wave energy transport and group velocity

1991 ◽  
Vol 89 (4B) ◽  
pp. 1971-1971
Author(s):  
Charles E. Bradley ◽  
David T. Blackstock
Keyword(s):  
Group Velocity ◽  
Wave Energy ◽  
Energy Transport ◽  
Bloch Wave

Subinertial Oscillations on the Amundsen Sea Shelf, Antarctica

2016 ◽  
Vol 46 (9) ◽  
pp. 2573-2582 ◽  
Author(s):  
A. K. Wåhlin ◽  
O. Kalén ◽  
K. M. Assmann ◽  
E. Darelius ◽  
H. K. Ha ◽  
...  
Keyword(s):  
Group Velocity ◽  
Rossby Waves ◽  
Half Width ◽  
Wave Spectra ◽  
Amundsen Sea ◽  
Western Flank ◽  
Shelf Region ◽  
Topographic Rossby Waves

AbstractMooring data from the western flank of Dotson trough, Amundsen Sea shelf region, show the presence of barotropic oscillations with a period of 40–80 h. The oscillations are visible in velocity, temperature, salinity, and pressure and are comparable to tides in magnitude. The period of the oscillations corresponds to topographic Rossby waves of low group velocity and a wavelength of about 40 km, that is, the half-width of the channel. It is suggested that these resonant topographic Rossby waves cause the observed peak in the wave spectra. The observations show that sparse CTD data from this region should be treated with caution and need to be complemented with moorings or yo-yo stations in order to give a representative picture for the hydrography.

scholarly journals The Impact of Atmospheric Rossby Waves and Cyclones On The Arctic Sea Ice Variability

2021 ◽  
Author(s):  
Marte Gé Hofsteenge ◽  
Rune Grand Graversen ◽  
Johanne Hope Rydsaa ◽  
Zoé Rey
Keyword(s):  
Sea Ice ◽  
Energy Transport ◽  
Rossby Waves ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Synoptic Scale ◽  
Sea Ice Concentration ◽  
Latent Energy ◽  
Arctic Sea ◽  
Ice Concentration

Abstract The Arctic sea-ice extent has strongly declined over recent decades. A large inter-annual variability is superimposed on this negative trend. Previous studies have emphasised a significant warming effect associated with latent energy transport into the Arctic region, in particular due to an enhanced greenhouse effect associated with the convergence of the humidity transport over the Arctic. The atmospheric energy transport into the Arctic is mostly accomplished by waves such as Rossby waves and cyclones. Here we present a systematic study of the effect on Arctic sea ice of these atmospheric wave types. Through a regression analysis we investigate the coupling between transport anomalies of both latent and dry-static energy and sea-ice anomalies. From the state-of-the-art ERA5 reanalysis product the latent and dry-static transport over the Arctic boundary (70 ºN) is calculated. The transport is then split into transport by planetary and synoptic-scale waves using a Fourier decomposition. The results show that latent energy transport as compared to that of dry-static shows a much stronger potential to decrease sea ice concentration. However, taking into account that the variability of dry-static transport is of an order of magnitude larger than latent, the actual impact on the sea ice appears similar for the two components. In addition, the energy transport by planetary waves causes a strong decline of the sea ice concentration whereas the transport by synoptic-scale waves shows only little effect on the sea ice. The study emphasises the importance of the large-scale waves on the sea ice variability.

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