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A 1/3 {$^\circ$} resolution model of the tropical Pacific Ocean is |
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used to investigate eddy energetics associated with tropical |
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instability waves (TIWs) in the equatorial Pacific Ocean from 1996 |
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to 2000. The geographical dependence of the balance of the perturbation |
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energy equation is explored, and the sensitivity of the results to |
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the wind forcing and the model's resolution is investigated. |
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Eddy kinetic energy reaches large values in fall 1998 |
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during La Nina and TIWs are absent during El Nino (spring 1997 to |
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spring 1998). At 135$^{\circ}$W, the large mean to eddy kinetic |
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energy conversion is dominated by $\overline{u'v'} \partial |
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U/\partial y$, $\overline{v'v'}\partial V/\partial y$ and |
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$\overline{u'w'}\partial U/\partial z$. All those terms are |
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subject to seasonal and interannual variability. Baroclinic instability also |
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provides energy to the TIWs between 1$^{\circ}$ and 4$^{\circ}$N through the |
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conversion of eddy potential to eddy kinetic energy. |
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Largest eddy energy production are observed in surface at 4$^{\circ}$N within |
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the anticyclonic shear between the SEC and the NECC, where the eddy kinetic energy |
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is maximum. $\overline{u'v'}\partial U/\partial y$ is maximum just north of the equator |
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at about 50\,m in fall 1996 while it is maximum at the surface |
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in fall 1998 and fall 1999, suggesting that the TIWs derive their energy |
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from the EUC-SEC shear in 1996 and from the shear within the SEC in 1998 |
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and 1999. $\overline{v'v'}\partial V/\partial y$ and $\overline{u'w'}\partial |
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U/\partial z$, which generally tend to weaken the waves just to the north |
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of the equator, are also subject to interannual variability and their combination |
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with $\overline{u'v'}\partial U/\partial y$ lead to weaker TIWs in fall |
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1996 compared to fall 1998 and 1999. |
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