Kelvin wave attenuation along nearly straight boundaries

1972 ◽  
Vol 53 (2) ◽  
pp. 273-286 ◽  
Author(s):  
H. G. Pinsent
Keyword(s):  
Incident Wave ◽  
Wave Attenuation ◽  
Plane Waves ◽  
Kelvin Waves ◽  
Kelvin Wave ◽  
Incident Wavelength ◽  
Reflected Waves ◽  
Linearized Theory ◽  
Coastal Boundary ◽  
Wave Problems

Two related wave problems are considered for a rotating sea of nearly uniform depth bounded by a coastline which is nearly straight. The depth changes are assumed to be independent of the distance from the coastline. The first problem, which is concerned with the origin of Kelvin waves in a coastal wave record, deals with a system of plane waves incident on the coastline and giving rise, in addition to reflected waves, to a Kelvin wave moving along the coast. Linearized theory is used to obtain details of the Kelvin wave for arbitrary perturbations in coastline and depth. Results suggest that the depth changes have their greatest effect in producing Kelvin waves if the incident wave crests are nearly parallel, but not exactly so, to the line of the depth changes. On the other hand when the wave crests are parallel to the coast, Kelvin waves are produced only by changes in the coastal boundary. In the second problem a Kelvin waye is assumed to be the incident wave. To find the energy propagated away from the coastline it is necessary to extend the theory to second order in the perturbations. It is shown that for a fixed wave period less than a pendulum day this energy has a maximum for a perturbation whose length is of comparable magnitude to the incident wavelength. Finally, the theory is applied to Kelvin waves propagating along the Californian coastline. Results obtained tend to confirm the suspicion that coastal irregularities are responsible for certain anomalies detected in tidal wave constituents by Munk, Snodgrass & Wimbush (1970).

Reflexion of Kelvin waves at the open end of a rotating semi-infinite channel

1969 ◽  
Vol 39 (2) ◽  
pp. 321-328 ◽  
Author(s):  
B. A. Packham
Keyword(s):  
Angular Velocity ◽  
North Sea ◽  
Resonance Effect ◽  
Kelvin Waves ◽  
Kelvin Wave ◽  
Rotating System ◽  
The North ◽  
Reflexion Coefficient ◽  
The North Sea ◽  
Linearized Theory

The problem of the reflexion of tides in an enclosed sea such as the North Sea at a point at which it either enters the ocean or its width suddenly increases is considered by investigating the reflexion of a Kelvin wave at the open end of a rotating uniform semi-infinite channel.It is shown that for a given channel, if the wave period is less than a pendulum day, then, according to the linearized theory of long waves in a rotating system, the reflexion coefficient increases with the angular velocity of rotation. It is also shown that there is a resonance effect for certain critical channel widths, namely, those at which extra modes within the channel become possible.

On the trapping of waves along a discontinuity of depth in a rotating ocean

1968 ◽  
Vol 31 (3) ◽  
pp. 417-434 ◽  
Author(s):  
M. S. Longuet-Higgins
Keyword(s):  
Shallow Water ◽  
Kelvin Waves ◽  
Wave Period ◽  
The Other ◽  
Kelvin Wave ◽  
Shallow Water Theory ◽  
Coriolis Parameter ◽  
Straight Line ◽  
Linearized Theory ◽  
The Waves

It is shown that, according to the linearized theory of long waves in a rotating, unbounded sea, if there is a discontinuity in depth along a straight line separating two regions each of uniform depth, then wave motions may exist which are propagated along the discontinuity and whose amplitude falls off exponentially to either side. Thus the discontinuity acts as a kind of wave-guide.The period of the waves is always greater than the inertial period. The wave period also exceeds the period of Kelvin waves in the deeper medium. As the ratio of the depth tends to infinity, the wave period tends to the inertial period or to the Kelvin wave period, whichever is the greater. On the other hand as the wavelength decreases (within the limits of shallow-water theory) so the waves tend to the non-divergent planetary waves found recently by Rhines.In an infinite ocean of uniform depth free waves with period greater than a pendulum-day cannot normally be propagated without attenuation (if the Coriolis parameter is constant). But non-uniformities of depth provide a means whereby such energy may be channelled over great distances with little attenuation.It is suggested that a gradually diminishing discontinuity will act as a chromatograph, each position along the discontinuity being marked by waves of a particular period.

Study of wave attenuation in concrete

1993 ◽  
Vol 8 (9) ◽  
pp. 2344-2353 ◽  
Author(s):  
J-M. Berthelot ◽  
Souda M. Ben ◽  
J.L. Robert
Keyword(s):  
Experimental Study ◽  
Plane Wave ◽  
Wave Attenuation ◽  
Plane Waves ◽  
Propagation Distance ◽  
Experimental Results ◽  
The Other ◽  
Wave Frequency ◽  
Concrete Composition ◽  
Analytical Expression

The experimental study of wave attenuation in concrete has been achieved in the case of the propagation of plane waves in concrete rods. Different mortars and concretes have been investigated. A transmitter transducer coupled to one of the ends of the concrete rod generates the propagation of a plane wave in the rod. The receiver transducer, similar to the previous one, is coupled to the other end of the rod. The experimental results lead to an analytical expression for wave attenuation as function of the concrete composition, the propagation distance, and the wave frequency.

scholarly journals Kelvin wave hydraulic control induced by interactions between vortices and topography

2011 ◽  
Vol 687 ◽  
pp. 194-208 ◽  
Author(s):  
Andrew McC. Hogg ◽  
William K. Dewar ◽  
Pavel Berloff ◽  
Marshall L. Ward
Keyword(s):  
Shallow Water ◽  
Analytical Solutions ◽  
Critical Condition ◽  
Numerical Models ◽  
Kelvin Waves ◽  
Water Model ◽  
Hydraulic Jumps ◽  
Hydraulic Control ◽  
Kelvin Wave ◽  
Shallow Water Model

AbstractThe interaction of a dipolar vortex with topography is examined using a combination of analytical solutions and idealized numerical models. It is shown that an anticyclonic vortex may generate along-topography flow with sufficient speeds to excite hydraulic control with respect to local Kelvin waves. A critical condition for Kelvin wave hydraulic control is found for the simplest case of a 1.5-layer shallow water model. It is proposed that in the continuously stratified case this mechanism may allow an interaction between low mode vortices and higher mode Kelvin waves, thereby generating rapidly converging isopycnals and hydraulic jumps. Thus, Kelvin wave hydraulic control may contribute to the flux of energy from mesoscale to smaller, unbalanced, scales of motion in the ocean.

scholarly journals Convectively Coupled Kelvin Waves: From Linear Theory to Global Models

2015 ◽  
Vol 73 (1) ◽  
pp. 407-428 ◽  
Author(s):  
Michael J. Herman ◽  
Zeljka Fuchs ◽  
David J. Raymond ◽  
Peter Bechtold
Keyword(s):  
Composite Structures ◽  
Large Scale ◽  
Kelvin Waves ◽  
Radiosonde Data ◽  
3D Analysis ◽  
Kelvin Wave ◽  
Scale Characteristics ◽  
Precipitation Anomalies ◽  
Convective Inhibition ◽  
Ecmwf Model

Abstract The authors analyze composite structures of tropical convectively coupled Kelvin waves (CCKWs) in terms of the theory of Raymond and Fuchs using radiosonde data, 3D analysis and reanalysis model output, and annual integrations with the ECMWF model on the full planet and on an aquaplanet. Precipitation anomalies are estimated using the NOAA interpolated OLR and TRMM 3B42 datasets, as well as using model OLR and rainfall diagnostics. Derived variables from these datasets are used to examine assumptions of the theory. Large-scale characteristics of wave phenomena are robust in all datasets and models where Kelvin wave variance is large. Indices from the theory representing column moisture and convective inhibition are also robust. The results suggest that the CCKW is highly dependent on convective inhibition, while column moisture does not play an important role.

Wave Steepness and Relative Width: Influence on Transmission Coefficient of Horizontal Interlaced, Multilayered, Moored Floating Pipe Breakwater With Five Layers

2011 ◽  
Vol 45 (5) ◽  
pp. 20-27
Author(s):  
Sacchi Rajappa ◽  
Arkal Vittal Hegde ◽  
Subba Rao ◽  
Veena Channegowda
Keyword(s):  
Physical Model ◽  
Transmission Coefficient ◽  
Wave Height ◽  
Incident Wave ◽  
Wave Attenuation ◽  
Transmitted Wave ◽  
Relative Width ◽  
Wave Steepness ◽  
Transmission Characteristics ◽  
Time Period

AbstractThis paper presents the results of a series of physical model scale experiments conducted to determine the transmission characteristics of a horizontal interlaced, multilayered, moored floating pipe breakwater. The studies are conducted on physical breakwater models having five layers of PVC pipes. The wave steepness (Hi/gT2, where Hi is incident wave height, g is acceleration due to gravity, and T is time period) was varied between 0.063 and 0.849, relative width (W/L, where W is width of breakwater and L is the wavelength) was varied between 0.4 and 2.65, and relative spacing (S/D, where S is horizontal centre to centre spacing of pipes and D is the diameter of pipes) was set equal to 2. The transmitted wave height is measured, and the gathered data are analyzed by plotting nondimensional graphs depicting the variation of Kt (transmission coefficient) with Hi/gT2 for values of d/W (d is depth of water) and of Kt with W/L for values of Hi/d. It is observed that Kt decreases as Hi/gT2 increases for the range of d/W between 0.082 and 0.139. It is also observed that Kt decreases with an increase in W/L values for the range of Hi/d from 0.06 to 0.40. The maximum wave attenuation achieved with the present breakwater configuration is 78%.

scholarly journals Tropical temperature variability and Kelvin-wave activity in the UTLS from GPS RO measurements

2017 ◽  
Vol 17 (2) ◽  
pp. 793-806 ◽  
Author(s):  
Barbara Scherllin-Pirscher ◽  
William J. Randel ◽  
Joowan Kim
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Wave Activity ◽  
Kelvin Waves ◽  
Temperature Variability ◽  
Stationary Waves ◽  
Kelvin Wave ◽  
Quasi Biennial Oscillation ◽  
Tropical Tropopause ◽  
Tropopause Region

Abstract. Tropical temperature variability over 10–30 km and associated Kelvin-wave activity are investigated using GPS radio occultation (RO) data from January 2002 to December 2014. RO data are a powerful tool for quantifying tropical temperature oscillations with short vertical wavelengths due to their high vertical resolution and high accuracy and precision. Gridded temperatures from GPS RO show the strongest variability in the tropical tropopause region (on average 3 K2). Large-scale zonal variability is dominated by transient sub-seasonal waves (2 K2), and about half of sub-seasonal variance is explained by eastward-traveling Kelvin waves with periods of 4 to 30 days (1 K2). Quasi-stationary waves associated with the annual cycle and interannual variability contribute about a third (1 K2) to total resolved zonal variance. Sub-seasonal waves, including Kelvin waves, are highly transient in time. Above 20 km, Kelvin waves are strongly modulated by the quasi-biennial oscillation (QBO) in stratospheric zonal winds, with enhanced wave activity during the westerly shear phase of the QBO. In the tropical tropopause region, however, peaks of Kelvin-wave activity are irregularly distributed in time. Several peaks coincide with maxima of zonal variance in tropospheric deep convection, but other episodes are not evidently related. Further investigations of convective forcing and atmospheric background conditions are needed to better understand variability near the tropopause.

scholarly journals Kelvin Waves and Tropical Cyclogenesis: A Global Survey

2015 ◽  
Vol 143 (10) ◽  
pp. 3996-4011 ◽  
Author(s):  
Carl J. Schreck
Keyword(s):  
Tropical Cyclone ◽  
Rainfall Variability ◽  
Kelvin Waves ◽  
Wave Crest ◽  
Tropical Cyclogenesis ◽  
Kelvin Wave ◽  
Easterly Waves ◽  
Easterly Wave ◽  
Show Evidence ◽  
Wave Passage

Abstract Convectively coupled atmospheric Kelvin waves are among the most prominent sources of synoptic-scale rainfall variability in the tropics, but large uncertainties surround their role in tropical cyclogenesis. This study identifies the modulation of tropical cyclones relative to the passage of a Kelvin wave’s peak rainfall (i.e., its crest) in each basin. Tropical cyclogenesis is generally inhibited for 3 days before the crest and enhanced for 3 days afterward. Composites of storms forming in the most favorable lags illustrate the dynamical impacts of the waves. In most basins, the tropical cyclone actually forms during the convectively suppressed phase of the wave. The 850-hPa equatorial westerly anomalies provide the cyclonic vorticity for the nascent storm, and 200-hPa easterly anomalies enhance the outflow. The wind anomalies persist at both levels longer than the Kelvin wave’s period and are often related to the Madden–Julian oscillation (MJO). The onset of these wind anomalies occurs with the Kelvin wave passage, while the MJO apparently establishes their duration. Many of the composites also show evidence of an easterly wave from which the tropical cyclone develops. The composite easterly wave amplifies or even initiates within the Kelvin wave crest. These results show the importance of Kelvin waves interacting with the MJO and easterly waves during tropical cyclogenesis. Given that Kelvin waves often circumnavigate the globe, these results show promise for long-range forecasting of tropical cyclogenesis in all basins.

scholarly journals The Spectrum of Convectively Coupled Kelvin Waves and the Madden–Julian Oscillation in Regions of Low-Level Easterly and Westerly Background Flow

2012 ◽  
Vol 69 (7) ◽  
pp. 2107-2111 ◽  
Author(s):  
Paul E. Roundy
Keyword(s):  
Longwave Radiation ◽  
Wave Dispersion ◽  
Warm Pool ◽  
Kelvin Waves ◽  
Madden Julian Oscillation ◽  
Westerly Wind ◽  
Kelvin Wave ◽  
Low Level ◽  
Geographical Regions ◽  
Zonal Wavenumber

Abstract The zonal wavenumber–frequency power spectrum of outgoing longwave radiation in the global tropics suggests that power in convectively coupled Kelvin waves and the Madden–Julian oscillation (MJO) is organized into two distinct spectral peaks with a minimum in power in between. This work demonstrates that integration of wavelet power in the wavenumber–frequency domain over geographical regions of moderate trade winds yields a similar pronounced spectral gap between these peaks. In contrast, integration over regions of background low-level westerly wind yields a continuum of power with no gap between the MJO and Kelvin bands. Results further show that signals in tropical convection are redder in frequency in these low-level westerly wind zones, confirming that Kelvin waves tend to propagate more slowly eastward over the warm pool than other parts of the world. Results are consistent with the perspective that portions of disturbances labeled as Kelvin waves and the MJO that are proximate to Kelvin wave dispersion curves exist as a continuum over warm pool regions.

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