Convectively coupled Kelvin wave propagation past Sumatra: A June case and corresponding composite analysis

Abstract Kelvin waves in the Pacific Ocean occasionally develop and propagate eastward together with anomalies of deep convection and low-level westerly wind. This pattern suggests coupling between the oceanic waves and atmospheric convection. A simple composite analysis based on observed coupled events from October through April demonstrates that this apparent coupled mode is associated with significant large anomalies in the global flow that extend to high latitudes. These high-latitude anomalies are significantly larger than those that are linearly associated with the El Niño–Southern Oscillation (ENSO), and they evolve on time scales between those of the Madden–Julian oscillation and ENSO, potentially providing an opportunity for enhanced subseasonal predictability in the flow of the global atmosphere.

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Buoyancy-Forced Downwelling in Boundary Currents

Journal of Physical Oceanography ◽

10.1175/2008jpo3993.1 ◽

2008 ◽

Vol 38 (12) ◽

pp. 2704-2721 ◽

Cited By ~ 11

Author(s):

Michael A. Spall

Keyword(s):

Boundary Layer ◽

Wave Propagation ◽

Heat Loss ◽

Mixed Layer ◽

General Circulation ◽

Mixed Layer Depth ◽

Kelvin Wave ◽

Surface Cooling ◽

Layer Depth ◽

Boundary Currents

Abstract The issue of downwelling resulting from surface buoyancy loss in boundary currents is addressed using a high-resolution, nonhydrostatic numerical model. It is shown that the net downwelling is determined by the change in the mixed layer density along the boundary. For configurations in which the density on the boundary increases in the direction of Kelvin wave propagation, there is a net downwelling within the domain. For cases in which the density decreases in the direction of Kelvin wave propagation, cooling results in a net upwelling within the domain. Symmetric instability within the mixed layer drives an overturning cell in the interior, but it does not contribute to the net vertical motion. The net downwelling is determined by the geostrophic flow toward the boundary and is carried downward in a very narrow boundary layer of width E1/3, where E is the Ekman number. For the calculations here, this boundary layer is O(100 m) wide. A simple model of the mixed layer temperature that balances horizontal advection with surface cooling is used to predict the net downwelling and its dependence on external parameters. This model shows that the net sinking rate within the domain depends not only on the amount of heat loss at the surface but also on the Coriolis parameter, the mixed layer depth (or underlying stratification), and the horizontal velocity. These results indicate that if one is to correctly represent the buoyancy-forced downwelling in general circulation models, then it is crucial to accurately represent the velocity and mixed layer depth very close to the boundary. These results also imply that processes that lead to weak mixing within a few kilometers of the boundary, such as ice formation or freshwater runoff, can severely limit the downwelling forced by surface cooling, even if there is strong heat loss and convection farther offshore.

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Tide characteristics and tidal wave propagation in the Persian Gulf

10.5194/os-2021-98 ◽

2021 ◽

Author(s):

S. Mahya Hoseini ◽

Mohsen Soltanpour

Keyword(s):

Wave Propagation ◽

Coriolis Force ◽

Persian Gulf ◽

Longitudinal Axis ◽

Tidal Wave ◽

Water Levels ◽

Kelvin Wave ◽

Numerical Tests ◽

The Persian Gulf ◽

Bed Friction

Abstract. A 2D hydrodynamic model is employed to study the characteristics of tidal wave propagation in the Persian Gulf (PG). The study indicates that tidal waves propagate from the Arabian Sea and the Gulf of Oman into the PG through the Strait of Hormuz. The numerical model is first validated using the measured water levels and current speeds around the PG and the principal tidal constituents of Admiralty tide tables. Considering the intermediate width of the PG, in comparison to Rossby deformation radius, the tidal wave propagates like a Kelvin wave on the boundaries. Whereas the continental shelf oscillation resonance of the basin is close to the period of diurnal constituents, the results show that the tide is mixed mainly semidiurnal. A series of numerical tests is also developed to study the various effects of geometry and bathymetry of the PG, Coriolis force, and bed friction on tidal wave deformation. Numerical tests reveal that the Coriolis force, combined with the geometry of the gulf, results in generation of different amphidromic systems of diurnal and semidiurnal constituents. The configuration of the bathymetry of the PG, with a shallow zone at the closed end of the basin that extends along its longitudinal axis in the southern half (asymmetrical cross section), results in the deformations of incoming and returning tidal Kelvin waves and consequently the shifts of amphidromic points (APs). The bed friction also results in the movements of the APs from the centerline to the south border of the gulf.

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The Role of Decadal Kelvin Wave in the Western of Sumatra and Along the South Coast of Java using Frequency-Wavenumber 2D Spectral Analysis

Journal of Geoscience Engineering Environment and Technology ◽

10.25299/jgeet.2020.5.1.3889 ◽

2020 ◽

Vol 5 (1) ◽

pp. 40-46

Author(s):

Hanah Khoirunnisa ◽

Reno Arif Rachman ◽

Nining Sari Ningsih ◽

Fadli Syamsudin

Keyword(s):

Wave Propagation ◽

Spectral Analysis ◽

Decadal Variability ◽

South Coast ◽

Height Anomaly ◽

Kelvin Wave ◽

Pass Filter ◽

Diagram Method ◽

Low Pass Filter ◽

West Sumatra

This study observed the decadal variability of the sea surface height anomaly (SSHA) and identified the decadal Kelvin wave propagation along west-Sumatra and south coast of Java. SSHA data and the vertical distribution of sea temperature for 64 years from HYCOM model resulted has already used in this research. There are several methods to identify the propagation of decadal Kelvin wave. These methods were low-pass filter by cut-off 1 and 8 years, visual analytic by using Hovmӧller diagram method, and frequency-wavenumber 2D spectral analysis to identify the Kelvin wave propagation and its period. The decadal Kelvin wave could be observed in west coast of Sumatra and along south coast of Java. There are three propagations of decadal Kelvin wave and their velocities were 1.029x10-3 m/s (1974 – 1976), 0.21 m/s (1985 – 1986), and 6.86x10-4 m/s for 1998 to 2001 trough west Sumatra and southern Java. The frequency-wavenumber 2D spectral analysis produced the improvement of Kelvin wave and it has the period of 7.25 years. The occurrence of the Kelvin wave has a relation to IOD index. The average of the IOD index when the decadal Kelvin wave was occurring must be the negative value, its value was a -0.21.

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Variations of Kelvin waves around the TTL region during the stratospheric sudden warming events in the Northern Hemisphere winter

Annales Geophysicae ◽

10.5194/angeo-34-331-2016 ◽

2016 ◽

Vol 34 (3) ◽

pp. 331-345 ◽

Cited By ~ 3

Author(s):

Yue Jia ◽

Shao Dong Zhang ◽

Fan Yi ◽

Chun Ming Huang ◽

Kai Ming Huang ◽

...

Keyword(s):

Zonal Wind ◽

Reanalysis Data ◽

Wave Activity ◽

Equatorial Region ◽

Kelvin Waves ◽

Composite Analysis ◽

Kelvin Wave ◽

Stratospheric Sudden Warming ◽

Tropical Tropopause ◽

Hemisphere Winter

Abstract. Spatial and temporal variabilities of Kelvin waves during stratospheric sudden warming (SSW) events are investigated by the ERA-Interim reanalysis data, and the results are validated by the COSMIC temperature data. A case study on an exceptionally large SSW event in 2009, and a composite analysis comprising 18 events from 1980 to 2013 are presented. During SSW events, the average temperature increases by 20 K in the polar stratosphere, while the temperature in the tropical stratosphere decreases by about 4 K. Kelvin wave with wave numbers 1 and 2, and periods 10–20 days, clearly appear around the tropical tropopause layer (TTL) during SSWs. The Kelvin wave activity shows obvious coupling with the convection localized in the India Ocean and western Pacific (Indo-Pacific) region. Detailed analysis suggests that the enhanced meridional circulation driven by the extratropical planetary wave forcing during SSW events leads to tropical upwelling, which further produces temperature decrease in the tropical stratosphere. The tropical upwelling and cooling consequently result in enhancement of convection in the equatorial region, which excites the strong Kelvin wave activity. In addition, we investigated the Kelvin wave acceleration to the eastward zonal wind anomalies in the equatorial stratosphere during SSW events. The composite analysis shows that the proportion of Kelvin wave contribution ranges from 5 to 35 % during SSWs, much larger than in the non-SSW mid-winters (less than 5 % in the stratosphere). However, the Kelvin wave alone is insufficient to drive the equatorial eastward zonal wind anomalies during the SSW events, which suggests that the effects of other types of equatorial waves may not be neglected.

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Interannual variability of Kelvin wave propagation in the wave guides of the equatorial Indian Ocean, the coastal Bay of Bengal and the southeastern Arabian Sea during 1993–2006

Deep Sea Research Part I Oceanographic Research Papers ◽

10.1016/j.dsr.2009.10.008 ◽

2010 ◽

Vol 57 (1) ◽

pp. 1-13 ◽

Cited By ~ 101

Author(s):

R.R. Rao ◽

M.S. Girish Kumar ◽

M. Ravichandran ◽

A.R. Rao ◽

V.V. Gopalakrishna ◽

...

Keyword(s):

Wave Propagation ◽

Indian Ocean ◽

Interannual Variability ◽

Bay Of Bengal ◽

Arabian Sea ◽

Equatorial Indian Ocean ◽

Kelvin Wave ◽

Southeastern Arabian Sea ◽

Wave Guides ◽

Coastal Bay

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Kelvin wave propagation along an irregular coastline

Journal of Fluid Mechanics ◽

10.1017/s0022112074002382 ◽

1974 ◽

Vol 64 (2) ◽

pp. 241-262 ◽

Cited By ~ 16

Author(s):

L. A. Mysak ◽

C. L. Tang

Keyword(s):

Wave Propagation ◽

Large Scale ◽

Wave Speed ◽

Kelvin Wave ◽

Coriolis Parameter ◽

California Coast ◽

Percentage Decrease ◽

Expansion Technique ◽

Stationary Random Function ◽

Siberian Coast

We discuss the theory of Kelvin wave propagation along an infinitely long coast-line which is straight except for small deviations which are treated as a stationary random function of distance along the coast. An operator expansion technique is used to derive the dispersion relation for the coherent Kelvin wave field. For the subinertial case σ = ω/f < 1 (ω = wave frequency, f = Coriolis parameter), it is shown that the wave speed is always decreased by the coastal irregularities. Moreover, while the coherent wave amplitude is unaltered, the energy flux along the coast is decreased by the irregularities. For the case σ > 1, however, we show that in the direction of propagation the wave is attenuated (with the energy being scattered into the random Poincaré and Kelvin wave modes) and that the wave speed is again decreased. Applications of the theory are made to the California coast and North Siberian coast to determine the decrease in phase velocity due to small coastal irregularities. For the California coast the percentage decrease is only about 1%. For the Siberian coast, however, the percentage decrease is about 25% for the K1 tide, and a minimum of 25% for the M2 tide. The attenuation of a Kelvin wave, however, appears to be due to very large scale irregularities. An estimate of the actual attenuation rate is not possible, though, because of the relatively short extent of coastal contours available for spectral analysis.Although attention in this paper has been focused on Kelvin wave propagation, the method developed could readily be used to study the behaviour of other classes of waves trapped against a randomly perturbed boundary.

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