The vertical structure of annual wave energy flux in the tropical Indian Ocean

AbstractA recently developed energy flux diagnosis scheme, which incorporates a smooth connection between the tropical and subtropical zones, is used in the present study to investigate vertically propagating waves in the tropical Indian Ocean (IO) based on the result of a linear, continuously stratified ocean model driven by climatological wind forcing. This extended diagnosis reveals deep-reaching eastward energy fluxes at the equator which develop four times per year and are associated with equatorial Kelvin waves (KWs) generated by semiannual winds. The authors find that the downward transfer of wave energy is particularly deep in the southern Bay of Bengal (SBoB). This downward flux is attributed to off-equatorial Rossby waves and appears four times per year, maximizing its amplitude during November–December. Southwesterly winds in the Arabian Sea intensify eastward energy flux of KWs at mid-depth, which maximizes in amplitude in August. This is contrastive to KW energy flux at the surface which peaks in May. These mid-depth equatorial KW packets subsequently arrive at the eastern boundary of the IO and are diffracted poleward to produce downward energy flux in November and December detected in the SBoB.

Download Full-text

The 1994 positive Indian Ocean Dipole event as investigated by the transfer routes of oceanic wave energy

Journal of Physical Oceanography ◽

10.1175/jpo-d-21-0189.1 ◽

2022 ◽

Keyword(s):

Indian Ocean ◽

Energy Flux ◽

Wave Energy ◽

Phase Speed ◽

Tropical Indian Ocean ◽

Basic Feature ◽

Ocean Model ◽

The Other ◽

Indian Ocean Dipole Event ◽

Positive Indian Ocean Dipole

Abstract The present study investigates the interannual variability of the tropical Indian Ocean (IO) based on the transfer routes of wave energy in a set of 61-year hindcast experiments using a linear ocean model. To understand the basic feature of the IO Dipole mode, this paper focuses on the 1994 pure positive event. Two sets of westward transfer episodes in the energy flux associated with Rossby waves (RWs) are identified along the equator during 1994. One set represents the same phase speed as the linear theory of equatorial RWs, while the other set is slightly slower than the theoretical phase speed. The first set originates from the reflection of equatorial Kelvin waves at the eastern boundary of the IO. On the other hand, the second set is found to be associated with off-equatorial RWs generated by southeasterly winds in the southeastern IO, which may account for the appearance of the slower group velocity. A combined empirical orthogonal function (EOF) analysis of energy-flux streamfunction and potential reveals the intense westward signals of energy flux are attributed to off-equatorial RWs associated with predominant wind input in the southeastern IO corresponding to the positive IO Dipole event.

Download Full-text

Momentum flux, energy flux and pressure drag associated with mountain wave across western ghat

MAUSAM ◽

10.54302/mausam.v52i2.1699 ◽

2021 ◽

Vol 52 (2) ◽

pp. 325-332

Author(s):

SOMENATH DUTTA

Keyword(s):

Energy Flux ◽

Wave Energy ◽

Momentum Flux ◽

Western Ghat ◽

Mountain Wave ◽

Pressure Drag ◽

Wave Energy Flux ◽

Vertically Propagating ◽

Flux Energy ◽

Wave Momentum

An attempt has been made to parameterize the wave momentum flux wave energy flux and pressure drag associated with mountain wave across the Mumbai-Pune section of western ghat mountain in India. A two dimensional frictionless, adiabatic, hydrostatic, Boussinesq flow with constant basic flow (U) and constant Brunt Vaisala frequency (N) across a mesoscale mountain with infinite extension in the Cross wind direction, has been considered here. It has been shown that for a vertically propagating (or decaying) waves the wave momentum flux is downward (or upward) and the wave energy flux is upward (or downward). It has also been shown that both the fluxes are independent of the half width of the bell shaped part of the western ghat. The analytically derived formula have been used to compute the pressure drag and to find out the vertical profile of wave momentum flux and wave energy flux for different cases of mountain wave across western ghat, as reported by earlier workers.

Download Full-text

Physical Mechanisms for the Maintenance of GCM-Simulated Madden–Julian Oscillation over the Indian Ocean and Pacific

Journal of Climate ◽

10.1175/2010jcli3759.1 ◽

2011 ◽

Vol 24 (10) ◽

pp. 2469-2482 ◽

Cited By ~ 9

Author(s):

Liping Deng ◽

Xiaoqing Wu

Keyword(s):

Indian Ocean ◽

Energy Flux ◽

Wave Energy ◽

Western Pacific ◽

Eastern Pacific ◽

Convective Heating ◽

Trigger Condition ◽

Wave Energy Flux ◽

The Indian Ocean ◽

Central Eastern

Abstract The kinetic energy budget is conducted to analyze the physical processes responsible for the improved Madden–Julian oscillation (MJO) simulated by the Iowa State University general circulation models (ISUGCMs). The modified deep convection scheme that includes the revised convection closure, convection trigger condition, and convective momentum transport (CMT) enhances the equatorial (10°S–10°N) MJO-related perturbation kinetic energy (PKE) in the upper troposphere and leads to a more robust and coherent eastward-propagating MJO signal. In the MJO source region, the Indian Ocean (45°–120°E), the upper-tropospheric MJO PKE is maintained by the vertical convergence of wave energy flux and the barotropic conversion through the horizontal shear of mean flow. In the convectively active region, the western Pacific (120°E–180°), the upper-tropospheric MJO PKE is supported by the convergence of horizontal and vertical wave energy fluxes. Over the central-eastern Pacific (180°–120°W), where convection is suppressed, the upper-tropospheric MJO PKE is mainly due to the horizontal convergence of wave energy flux. The deep convection trigger condition produces stronger convective heating that enhances the perturbation available potential energy (PAPE) production and the upward wave energy fluxes and leads to the increased MJO PKE over the Indian Ocean and western Pacific. The trigger condition also enhances the MJO PKE over the central-eastern Pacific through the increased convergence of meridional wave energy flux from the subtropical latitudes of both hemispheres. The revised convection closure affects the response of mean zonal wind shear to the convective heating over the Indian Ocean and leads to the enhanced upper-tropospheric MJO PKE through the barotropic conversion. The stronger eastward wave energy flux due to the increase of convective heating over the Indian Ocean and western Pacific by the revised closure is favorable to the eastward propagation of MJO and the convergence of horizontal wave energy flux over the central-eastern Pacific. The convection-induced momentum tendency tends to decelerate the upper-tropospheric wind, which results in a negative work to the PKE budget in the upper troposphere. However, the convection momentum tendency accelerates the westerly wind below 800 hPa over the western Pacific, which is partially responsible for the improved MJO simulation.

Download Full-text

Joint Modelling of Wave Energy Flux and Wave Direction

Processes ◽

10.3390/pr9030460 ◽

2021 ◽

Vol 9 (3) ◽

pp. 460

Author(s):

Takvor H. Soukissian ◽

Flora E. Karathanasi

Keyword(s):

Energy Flux ◽

Wave Energy ◽

Goodness Of Fit ◽

North Atlantic Ocean ◽

Wave Climate ◽

Western Mediterranean ◽

Wave Direction ◽

Bivariate Model ◽

The North ◽

Wave Energy Flux

In the context of wave resource assessment, the description of wave climate is usually confined to significant wave height and energy period. However, the accurate joint description of both linear and directional wave energy characteristics is essential for the proper and detailed optimization of wave energy converters. In this work, the joint probabilistic description of wave energy flux and wave direction is performed and evaluated. Parametric univariate models are implemented for the description of wave energy flux and wave direction. For wave energy flux, conventional, and mixture distributions are examined while for wave direction proven and efficient finite mixtures of von Mises distributions are used. The bivariate modelling is based on the implementation of the Johnson–Wehrly model. The examined models are applied on long-term measured wave data at three offshore locations in Greece and hindcast numerical wave model data at three locations in the western Mediterranean, the North Sea, and the North Atlantic Ocean. A global criterion that combines five individual goodness-of-fit criteria into a single expression is used to evaluate the performance of bivariate models. From the optimum bivariate model, the expected wave energy flux as function of wave direction and the distribution of wave energy flux for the mean and most probable wave directions are also obtained.

Download Full-text

Tail effects in the third post-Newtonian gravitational wave energy flux of compact binaries in quasi-elliptical orbits

Physical Review D ◽

10.1103/physrevd.77.064034 ◽

2008 ◽

Vol 77 (6) ◽

Cited By ~ 49

Author(s):

K. G. Arun ◽

Luc Blanchet ◽

Bala R. Iyer ◽

Moh’d S. S. Qusailah

Keyword(s):

Gravitational Wave ◽

Energy Flux ◽

Wave Energy ◽

Compact Binaries ◽

The Third ◽

Wave Energy Flux ◽

Elliptical Orbits

Download Full-text

Horizontal energy flux of wind-driven intraseasonal waves in the tropical Atlantic by a unified diagnosis

Journal of Physical Oceanography ◽

10.1175/jpo-d-20-0262.1 ◽

2021 ◽

Author(s):

Qingyang Song ◽

Hidenori Aiki

Keyword(s):

Energy Flux ◽

Wave Energy ◽

Horizontal Distribution ◽

Kelvin Waves ◽

Asymmetric Distribution ◽

Central Basin ◽

Tropical Atlantic ◽

Equatorial Wave ◽

Wave Energy Flux ◽

Velocity Anomalies

AbstractIntraseasonal waves in the tropical Atlantic Ocean have been found to carry prominent energy that affects interannual variability of zonal currents. This study investigates energy transfer and interaction of wind-driven intraseasonal waves using single-layer model experiments. Three sets of wind stress forcing at intraseasonal periods of around 30 days, 50 days and 80 days with a realistic horizontal distribution are employed separately to excite the second baroclinic mode in the tropical Atlantic. A unified scheme for calculating the energy flux, previously approximated and used for the diagnosis of annual Kelvin and Rossby waves, is utilized in the present study in its original form for intraseasonal waves. Zonal velocity anomalies by Kelvin waves dominate the 80-day scenario. Meridional velocity anomalies by Yanai waves dominate the 30-day scenario. In the 50-day scenario, the two waves have comparable magnitudes. The horizontal distribution of wave energy flux is revealed. In the 30-day and 50-day scenarios, a zonally alternating distribution of cross-equatorial wave energy flux is found. By checking an analytical solution excluding Kelvin waves, we confirm that the cross-equatorial flux is caused by the meridional transport of geopotential at the equator. This is attributed to the combination of Kelvin and Yanai waves and leads to the asymmetric distribution of wave energy in the central basin. Coastally-trapped Kelvin waves along the African coast are identified by along-shore energy flux. In the north, the bend of the Guinea coast leads the flux back to the equatorial basin. In the south, the Kelvin waves strengthened by local wind transfer the energy from the equatorial to Angolan regions.

Download Full-text

Another Note on Rossby Wave Energy Flux

Journal of Physical Oceanography ◽

10.1175/jpo-d-19-0237.1 ◽

2020 ◽

Vol 50 (2) ◽

pp. 531-534

Author(s):

Theodore S. Durland ◽

J. Thomas Farrar

Keyword(s):

Group Velocity ◽

Energy Flux ◽

Rossby Wave ◽

Wave Energy ◽

Energy Equation ◽

Divergent Part ◽

Pressure Work ◽

Wave Energy Flux ◽

The Difference ◽

Definition Of

AbstractLonguet-Higgins in 1964 first pointed out that the Rossby wave energy flux as defined by the pressure work is not the same as that defined by the group velocity. The two definitions provide answers that differ by a nondivergent vector. Longuet-Higgins suggested that the problem arose from ambiguity in the definition of energy flux, which only impacts the energy equation through its divergence. Numerous authors have addressed this issue from various perspectives, and we offer one more approach that we feel is more succinct than previous ones, both mathematically and conceptually. We follow the work described by Cai and Huang in 2013 in concluding that there is no need to invoke the ambiguity offered by Longuet-Higgins. By working directly from the shallow-water equations (as opposed to the more involved quasigeostrophic treatment of Cai and Huang), we provide a concise derivation of the nondivergent pressure work and demonstrate that the two energy flux definitions are equivalent when only the divergent part of the pressure work is considered. The difference vector comes from the nondivergent part of the geostrophic pressure work, and the familiar westward component of the Rossby wave group velocity comes from the divergent part of the geostrophic pressure work. In a broadband wave field, the expression for energy flux in terms of a single group velocity is no longer meaningful, but the expression for energy flux in terms of the divergent pressure work is still valid.

Download Full-text