A modeling study of the impact of tropical instability waves on the heat budget of the eastern Equatorial Pacific
A modeling study of the impact of tropical instability waves on the heat budget of the eastern Equatorial Pacific
A numerical simulation is used to investigate the mixed layer heat balance of the tropical Pacific Ocean including the equatorial cold tongue and the region of vortices associated with tropical instability waves (TIWs). The study is motivated by a need to quantify the effects that TIWs have on the climatological heat budget of the cold tongue mixed layer; there has been some discrepancy between observations indicating very large equatorward heat transport by TIWs and models that disagree on the full three-dimensional budget. Validation of the model reveals that the TIW-induced circulation patterns are realistic but may have amplitudes about 15% weaker than those in the observations. The SST budget within tropical instabilities is first examined in a frame of reference moving with the associated tropical instability vortices (TIVs). Zonal advection of temperature anomalies and meridional advection of temperature by current anomalies dominate horizontal advection. These effects strongly heat the cold cusps and slightly cool the downwelling areas located at the leading edge of the vortices. Cooling by vertical mixing is structured at the vortex scale and almost compensates for horizontal advective heating in the cold cusps. In contrast to some previous studies, TIW-induced vertical advection is found to be negligible in the SST budget. Cooling by this term is only significant below the mixed layer. The effect of TIWs on the climatological heat budget is then investigated for the region bounded by 2°S–6°N, 160°–90°W, where instabilities are most active. TIW-induced horizontal advection leads to a warming of 0.84°C month?1, which is of the same order as the 0.77°C month?1 warming effect of atmospheric fluxes, while the mean currents and vertical mixing cool the upper ocean by ?0.59°C month?1 and ?1.06°C month?1, respectively. The cooling effect of TIW-induced vertical advection is also negligible in the long-term surface layer heat budget and only becomes significant below the mixed layer. The results above, and in particular the absence of cancellation between horizontal and vertical TIW-induced eddy advection, are robust in three other sensitivity experiments involving different mixing parameterizations and increased vertical resolution.
847-865
Menkes, Christophe E.R.
d66d14b1-f694-44c1-a573-13509d66aef3
Vialard, Jérôme G.
28e3cc0f-3c1e-43b3-97ff-a0c09e8d48f2
Kennan, Sean C.
5003ec02-5287-47af-8132-b139b964cb95
Boulanger, Jean-Philippe
2eeb7809-de43-4e65-994f-c9a8e91eaa2b
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
May 2006
Menkes, Christophe E.R.
d66d14b1-f694-44c1-a573-13509d66aef3
Vialard, Jérôme G.
28e3cc0f-3c1e-43b3-97ff-a0c09e8d48f2
Kennan, Sean C.
5003ec02-5287-47af-8132-b139b964cb95
Boulanger, Jean-Philippe
2eeb7809-de43-4e65-994f-c9a8e91eaa2b
Madec, Gurvan
ffb28deb-4bbd-4a4c-914f-492f813e4864
Menkes, Christophe E.R., Vialard, Jérôme G., Kennan, Sean C., Boulanger, Jean-Philippe and Madec, Gurvan
(2006)
A modeling study of the impact of tropical instability waves on the heat budget of the eastern Equatorial Pacific.
Journal of Physical Oceanography, 36 (5), .
(doi:10.1175/JPO2904.1).
Abstract
A numerical simulation is used to investigate the mixed layer heat balance of the tropical Pacific Ocean including the equatorial cold tongue and the region of vortices associated with tropical instability waves (TIWs). The study is motivated by a need to quantify the effects that TIWs have on the climatological heat budget of the cold tongue mixed layer; there has been some discrepancy between observations indicating very large equatorward heat transport by TIWs and models that disagree on the full three-dimensional budget. Validation of the model reveals that the TIW-induced circulation patterns are realistic but may have amplitudes about 15% weaker than those in the observations. The SST budget within tropical instabilities is first examined in a frame of reference moving with the associated tropical instability vortices (TIVs). Zonal advection of temperature anomalies and meridional advection of temperature by current anomalies dominate horizontal advection. These effects strongly heat the cold cusps and slightly cool the downwelling areas located at the leading edge of the vortices. Cooling by vertical mixing is structured at the vortex scale and almost compensates for horizontal advective heating in the cold cusps. In contrast to some previous studies, TIW-induced vertical advection is found to be negligible in the SST budget. Cooling by this term is only significant below the mixed layer. The effect of TIWs on the climatological heat budget is then investigated for the region bounded by 2°S–6°N, 160°–90°W, where instabilities are most active. TIW-induced horizontal advection leads to a warming of 0.84°C month?1, which is of the same order as the 0.77°C month?1 warming effect of atmospheric fluxes, while the mean currents and vertical mixing cool the upper ocean by ?0.59°C month?1 and ?1.06°C month?1, respectively. The cooling effect of TIW-induced vertical advection is also negligible in the long-term surface layer heat budget and only becomes significant below the mixed layer. The results above, and in particular the absence of cancellation between horizontal and vertical TIW-induced eddy advection, are robust in three other sensitivity experiments involving different mixing parameterizations and increased vertical resolution.
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Published date: May 2006
Identifiers
Local EPrints ID: 64362
URI: http://eprints.soton.ac.uk/id/eprint/64362
ISSN: 0022-3670
PURE UUID: 6fe0f379-fe87-4c89-875b-7e273282072d
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Date deposited: 10 Dec 2008
Last modified: 15 Mar 2024 11:48
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Contributors
Author:
Christophe E.R. Menkes
Author:
Jérôme G. Vialard
Author:
Sean C. Kennan
Author:
Jean-Philippe Boulanger
Author:
Gurvan Madec
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