Equatorial dynamics in a model

McCreary, Julian P.; Yu, Zuojun

doi:10.1016/0079-6611(92)90003-i

Cited by 102 publications

(87 citation statements)

References 66 publications

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“…At the end of the spin-up, the model reaches a statistically steady state. As in McCreary and Yu [1992], the only internal variability that appears in this experiment takes the form of TIWs, and will be described in the next section. Two extra years are run, and are used as the control (uncoupled) integration.…”

Section: Methodsmentioning

confidence: 99%

Influence of ocean‐atmosphere coupling on the properties of tropical instability waves

Pezzi

2004

Geophysical Research Letters

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[1] In this study we investigate how the modulation of surface wind-stress by tropical instability waves (TIWs) feeds back onto TIWs and plays a role in their fundamental properties. An ocean general circulation model is used, that reproduces qualitatively well the properties of TIWs when forced by climatological winds, although with a 30% underestimated amplitude. The ocean model is coupled to the atmosphere through a simple parameterization of the wind stress response to SST. The properties of the TIWs in the coupled simulations are compared with those without active coupling. Active coupling results in a negative feedback on TIWs, slightly reducing their temperature and meridional current variability, both at the surface and sub-surface. This reduced activity modulates the meridional heat and momentum transport, resulting in modest changes to the mean state, with a cooler cold tongue and stronger equatorial currents.

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Section: Methodsmentioning

confidence: 99%

Influence of ocean‐atmosphere coupling on the properties of tropical instability waves

Pezzi

2004

Geophysical Research Letters

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“…These tropical instability waves (TIWs) are generated from barotropic and baroclinic instabilities associated with the horizontal and vertical shear of equatorial current systems and related density gradients [e.g., Philander, 1978;Weisberg and Weingartner, 1988;McCreary and Yu, 1992;Masina et al, 1999;Grodsky et al, 2005;Jochum et al, 2004;Lyman et al, 2007;von Schuckmann et al, 2008]. The magnitudes of TIW-related variability as seen from different oceanic parameters exhibits regional and temporal variations, varying on seasonal to interannual time scales in association with changes in the equatorial current systems.…”

Section: Introductionmentioning

confidence: 99%

The influence of salinity on tropical Atlantic instability waves

et al. 2014

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Sea surface salinity (SSS) data derived from the Aquarius/SAC-D satellite mission are analyzed along with other satellite and in situ data to assess Aquarius' capability to detect tropical instability waves (TIWs) and eddies in the tropical Atlantic Ocean and to investigate the influence that SSS has on the variability. Aquarius data show that the magnitude of SSS anomalies associated with the Atlantic TIWs is 60.25 practical salinity unit, which is weaker than those in the Pacific by 50%. In the central equatorial Atlantic, SSS contribution to the mean meridional density gradient is similar to sea surface temperature (SST) contribution. Consequently, SSS is important to TIW-related surface density anomalies and perturbation potential energy (PPE). In this region, SSS influences surface PPE significantly through the direct effect and the indirect effect associated with SSS-SST covariability. Ignoring SSS effects would underestimate TIW-related PPE by approximately three times in the surface layer. SSS also regulates the seasonality of the TIWs. The borealspring peak of the PPE due to SSS leads that due to SST by about one month. Therefore, SSS not only affects the spatial structure, but the seasonal variability of the TIWs in the equatorial Atlantic. In the northeast Atlantic near the Amazon outflow and the North Brazil Current retroflection region and in the southeast Atlantic near the Congo River outflow, SSS accounts for 80-90% of the contribution to mean meridional density gradient. Not accounting for SSS effect would underestimate surface PPE in these regions by a factor of 10 and 4, respectively.

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“…However, Semtner and Holland (1980) and Cox (1980) found an instability with similar wavelength and period in a numerical simulation of a continuously stratified ocean and demonstrated that baroclinic instability represents a significant energy source for the growing unstable waves. In this work, we investigate the possible mean-flow configurations that show some characteristics similar to those of the equatorial Pacific and that are unstable to waves that have a spatial structure and a temporal periodicity similar to those observed (Legeckis, 1977;Qiao and Weisberg, 1995;Kennan and Flament, 2000) and simulated McCreary and Yu, 1992;Donohue and Wimbush, 1998;Proehl, 1998). Emphasis is placed on the effects of stratification on the instability waves.…”

Section: Introductionmentioning

confidence: 99%

Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

Masina

2002

Ann. Geophys.

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Abstract.Several numerical experiments are performed in a nonlinear, multi-level periodic channel model centered on the equator with different zonally uniform background flows which resemble the South Equatorial Current (SEC). Analysis of the simulations focuses on identifying stability criteria for a continuously stratified fluid near the equator. A 90 m deep frontal layer is required to destabilize a zonally uniform, 10 • wide, westward surface jet that is symmetric about the equator and has a maximum velocity of 100 cm/s. In this case, the phase velocity of the excited unstable waves is very similar to the phase speed of the Tropical Instability Waves (TIWs) observed in the eastern Pacific Ocean. The vertical scale of the baroclinic waves corresponds to the frontal layer depth and their phase speed increases as the vertical shear of the jet is doubled. When the westward surface parabolic jet is made asymmetric about the equator, in order to simulate more realistically the structure of the SEC in the eastern Pacific, two kinds of instability are generated. The oscillations that grow north of the equator have a baroclinic nature, while those generated on and very close to the equator have a barotropic nature.This study shows that the potential for baroclinic instability in the equatorial region can be as large as at mid-latitudes, if the tendency of isotherms to have a smaller slope for a given zonal velocity, when the Coriolis parameter vanishes, is compensated for by the wind effect.

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Equatorial dynamics in a model

Cited by 102 publications

References 66 publications

Influence of ocean‐atmosphere coupling on the properties of tropical instability waves

Influence of ocean‐atmosphere coupling on the properties of tropical instability waves

The influence of salinity on tropical Atlantic instability waves

Instabilities of continuously stratified zonal equatorial jets in a periodic channel model

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