Observations of long period waves in the tropical oceans and atmosphere

Luther, Douglas S.

doi:10.1575/1912/1690

Cited by 49 publications

(39 citation statements)

References 43 publications

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“…The idea of excess energy accumulating at the wavenumber of vanishing group velocity is physically reasonable, and in the summary we discuss some of the conditions proposed by Luther (1980) under which this might occur. The tenacity of the idea that such a physical process was demonstrated theoretically by WG is somewhat curious, however, because it is not in fact what the mathematics of WG predicted.…”

Section: Introductionmentioning

confidence: 90%

“…This led to the prescient observation that the oceanic peaks must be forced by winds concentrated in a relatively narrow low-wavenumber band: their other hypothesis. This prediction has been borne out (e.g., Luther 1980;Farrar and Durland 2012), and it appears that the locations of the spectral peaks in equatorial sea level may owe more to the concentration of equatorial wind energy in low wavenumbers than to special characteristics of the vanishing-group-velocity locus (see Farrar and Durland 2012).…”

Section: Introductionmentioning

confidence: 98%

“…The short sea level records did not allow WG to distinguish between the two predictions, but their mathematical analysis suggested that the latter of these hypotheses was the more likely. Nevertheless, the association of oceanic resonances with vanishing group velocity has lived on to the extent that subsequent authors have stated or implied that we might expect to find excess energy at the wavenumber of vanishing zonal group velocity and have cited WG as the source of the expectation (e.g., LeBlond and Mysak 1978;Luther 1980;Garzoli and Katz 1981;Lin et al 2008;Ferrari and Wunsch 2010).…”

Section: Introductionmentioning

confidence: 99%

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The Wavenumber–Frequency Content of Resonantly Excited Equatorial Waves

Durland

Farrar

2012

Journal of Physical Oceanography

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The theoretical resonant excitation of equatorial inertia-gravity waves and mixed Rossby-gravity waves is examined. Contrary to occasionally published expectations, solutions show that winds that are broadband in both zonal wavenumber and frequency do not in general produce peaks in the wavenumber-frequency spectrum of sea surface height (SSH) at wavenumbers associated with vanishing zonal group velocity.Excitation of total wave energy in inertia-gravity modes by broadband zonal winds is virtually wavenumber independent when the meridional structure of the winds does not impose a bias toward negative or positive zonal wavenumbers. With increasing wavenumber magnitude jkj, inertia-gravity waves asymptote toward zonally propagating pure gravity waves, in which the magnitude of meridional velocity y becomes progressively smaller relative to the magnitude of zonal velocity u and pressure p. When the total wave energy is independent of wavenumber, this effect produces a peak in jyj 2 near the wavenumber where group velocity vanishes, but a trough in jpj 2 (or SSH variance). Another consequence of the shift toward pure gravity wave structure is that broadband meridional winds excite inertia-gravity modes progressively less efficiently as jkj increases and y becomes less important to the wave structure. Broadband meridional winds produce a low-wavenumber peak in total wave energy leading to a subtle elevation of jpj 2 at low wavenumbers, but this is due entirely to the decrease in the forcing efficiency of meridional winds with increasing jkj, rather than to the vanishing of the group velocity. Physical conditions that might alter the above conclusions are discussed.

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Section: Introductionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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The Wavenumber–Frequency Content of Resonantly Excited Equatorial Waves

Durland

Farrar

2012

Journal of Physical Oceanography

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“…A 60 day wave period was chosen because¯uctuations of 40±60 day periods have been found in sea level records of the Paci®c Ocean (Luther, 1980) and could be related to ENSO Julian, 1971, 1972;En®eld, 1987;McPhaden and Taft, 1988). …”

Section: Intraseasonal Variabilitymentioning

confidence: 99%

Reflection of equatorial Kelvin waves at eastern ocean boundaries Part I: hypothetical boundaries

Soares¹,

Wainer

Wells

1999

Ann Geophysicae

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Abstract. A baroclinic shallow-water model is developed to investigate the eect of the orientation of the eastern ocean boundary on the behavior of equatorial Kelvin waves. The model is formulated in a spherical polar coordinate system and includes dissipation and nonlinear terms, eects which have not been previously included in analytical approaches to the problem. Both equatorial and middle latitude response are considered given the large latitudinal extent used in the model. Baroclinic equatorial Kelvin waves of intraseasonal, seasonal and annual periods are introduced into the domain as pulses of ®nite width. Their subsequent re¯ection, transmission and dissipation are investigated. It is found that dissipation is very important for the transmission of wave energy along the boundary and for re¯ections from the boundary. The dissipation was found to be dependent not only on the presence of the coastal Kelvin waves in the domain, but also on the period of these coastal waves. In particular the dissipation increases with wave period. It is also shown that the equatorial b-plane approximation can allow an anomalous generation of Rossby waves at higher latitudes. Nonlinearities generally have a small eect on the solutions, within the con®nes of this model.

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“…Wunsch and Gill [1976] first identified these waves in sea level records, and others [Weisberg et al, 1979;Luther, 1980;Eriksen, 1982;Garzoli and Katz, 1981;Chiswell et al, 1987] have verified their existence in all basins using sea level, dynamic height and velocity records. Evidence suggests that these waves are seasonally modulated [Garzoli, 1984], and Luther [1980] has provided evidence of zonal modulations as well. These modulations have been difficult to study in detail using the available in situ data, which motivates our attempt to use the now decadal long global coverage afforded by satellite altimeters to study these waves.…”

Section: Introductionmentioning

confidence: 98%

Equatorial inertia‐gravity waves observed in TOPEX/Poseidon sea surface heights

Gilbert

Mitchum

2001

Geophysical Research Letters

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Abstract.We report an evaluation of the ability of the TOPEX/Poseidon altimeter to observe equatorial inertiagravity waves in the central Pacific. Aliasing problems limit us to examining meridional mode two, but this mode is an energetic one in the Pacific basin. These estimates of the temporal potential energy modulations are compared with estimates from tide gauges in the tropical Pacific, and we find that the time series obtained at these points show good agreement.

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Observations of long period waves in the tropical oceans and atmosphere

Cited by 49 publications

References 43 publications

The Wavenumber–Frequency Content of Resonantly Excited Equatorial Waves

The Wavenumber–Frequency Content of Resonantly Excited Equatorial Waves

Reflection of equatorial Kelvin waves at eastern ocean boundaries Part I: hypothetical boundaries

Equatorial inertia‐gravity waves observed in TOPEX/Poseidon sea surface heights

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