scholarly journals Observed Dispersion Relation of Yanai Waves and 17-Day Tropical Instability Waves in the Pacific Ocean

SOLA ◽  
2010 ◽  
Vol 6 ◽  
pp. 17-20 ◽  
Author(s):  
Toshiaki Shinoda
Keyword(s):  
Dispersion Relation ◽  
Pacific Ocean ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
The Pacific ◽  
The Pacific Ocean

scholarly journals Barotropic Rossby Waves Radiating from Tropical Instability Waves in the Pacific Ocean

2011 ◽  
Vol 41 (6) ◽  
pp. 1160-1181 ◽  
Author(s):  
J. Thomas Farrar
Keyword(s):  
Dispersion Relation ◽  
Pacific Ocean ◽  
Sea Level ◽  
Rossby Waves ◽  
North Pacific Subtropical Gyre ◽  
Sea Level Variability ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
The Pacific ◽  
The Pacific Ocean

Abstract Tropical instability waves are triggered by instabilities of the equatorial current systems, and their sea level signal, with peak amplitude near 5°N, is one of the most prominent features of the dynamic topography of the tropics. Cross-spectral analysis of satellite altimetry observations shows that there is sea level variability in the Pacific Ocean as far north as Hawaii (i.e., 20°N) that is coherent with the sea level variability near 5°N associated with tropical instability waves. Within the uncertainty of the analysis, this off-equatorial variability obeys the dispersion relation for nondivergent, barotropic Rossby waves over a fairly broad range of periods (26–38 days) and zonal wavelengths (9°–23° of longitude) that are associated with tropical instability waves. The dispersion relation and observed wave properties further suggest that the waves are carrying energy away from the instabilities toward the North Pacific subtropical gyre, which, together with the observed coherence of the sea level signal of the barotropic waves with that of the tropical instability waves, suggests that the barotropic Rossby waves are being radiated from the tropical instability waves. The poleward transport of kinetic energy and westward momentum by these barotropic Rossby waves may influence the circulation in the subtropics.

scholarly journals Distinct 17- and 33-Day Tropical Instability Waves in Subsurface Observations*

2007 ◽  
Vol 37 (4) ◽  
pp. 855-872 ◽  
Author(s):  
John M. Lyman ◽  
Gregory C. Johnson ◽  
William S. Kessler
Keyword(s):  
Temporal Structure ◽  
Thermocline Depth ◽  
Subsurface Temperature ◽  
Instability Waves ◽  
Tropical Instability Waves ◽  
Meridional Velocity ◽  
The Pacific ◽  
The Pacific Ocean ◽  
Half Degree ◽  
Temperature Time

Abstract Tropical instability waves (TIWs) within a half-degree of the equator in the Pacific Ocean have been consistently observed in meridional velocity with periods of around 20 days. On the other hand, near 5°N, TIWs have been observed in sea surface height (SSH), thermocline depth, and velocity to have periods near 30 days. Tropical Atmosphere–Ocean (TAO) Project moored equatorial velocity and temperature time series are used to investigate the spatial and temporal structure of TIWs during 3 years of La Niña conditions from 1998 through 2001. Along 140°W, where the TIW temperature and velocity variabilities are at their maxima, these variabilities include two distinct TIWs with periods of 17 and 33 days, rather than one broadbanded process. As predicted by modeling studies, the 17-day TIW variability is shown to occur not only in meridional velocity at the equator, but also in subsurface temperature at 2°N and 2°S, while the 33-day TIW variability is observed primarily in subsurface temperature at 5°N. These two TIWs, respectively, are shown to have characteristics similar to a Yanai wave/surface-trapped instability and an unstable first meridional mode Rossby wave. One implication of such a description is that the velocity variability on the equator is not directly associated with the dominant 33-day variability along 5°N.

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