A Midlatitude–ENSO Teleconnection Mechanism via Baroclinically Unstable Long Rossby Waves
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CitationGalanti, Eli, and Ei Tziperman. 2003. A mid-latitude enso teleconnection mechanism via baroclinically unstable long rossby waves. Journal of Physical Oceanography 33(9): 1877-1888.
AbstractThe possibility of generating decadal ENSO variability via an ocean teleconnection to the midlatitude Pacific
is studied. This is done by analyzing the sensitivity of the equatorial stratification to midlatitude processes using
an ocean general circulation model, the adjoint method, and a quasigeostrophic normal-mode stability analysis.
It is found that, on timescales of 2–15 yr, the equatorial Pacific is most sensitive to midlatitude planetary Rossby
waves traveling from the midlatitudes toward the western boundary and then to the equator. Those waves that
propagate through baroclinically unstable parts of the subtropical gyre are amplified by the baroclinic instability
and therefore dominate the midlatitude signal arriving at the equator. This result implies that decadal variability
in the midlatitude Pacific would be efficiently transmitted to the equatorial Pacific from specific areas of the
midlatitude Pacific that are baroclinically unstable, such as the near-equatorial edges of the subtropical gyres
(158N and 128S). The Rossby waves that propagate via the baroclinically unstable areas are of the advective
mode type, which follow the gyre circulation to some degree and arrive from as far as 258N and 308S in the
east Pacific. It is shown that the baroclinic instability amplifying these waves involves critical layers due to the
vertical shear of the subtropical gyre circulation, at depths of 150–200 m.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:3630268
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