Publication Date:
2017-04-04
Description:
The instability processes
which generate unstable waves with chara-
cteristics similar to observed
tropical instability waves in the Pacific Ocean are
examined through a local energy analysis based on deviations from the time mean
flow. Numerical experiments indicate that the waves develop preferentially in the
eastern Pacific along the northern temperature front and have a westward phase
speed and a structure with two peaks in amplitude: one located on the equator
and the other a few degrees
north of it. The energy analysis shows that the
"two-peak" structure of the eastern waves is explained by two different instability
processes
which occur at different latitudes. In the time mean sense
the region
north of the equator is baroclinically unstable, while barotropic instability prevails
at the equator. The life cycle of the waves is revealed by the time evolution of
the energetics. Baroclinic instability is the dominant triggering mechanism
which
induces growth of the waves along the northern temperature front. The eddy
pressure
fluxes radiate energy south of the equator where the rneridional shear
between the Equatorial Undercurrent and the South Equatorial Current becomes
barotropically unstable. From the numerical simulations, there is evidence of
a second
unstable region in the central Pacific south of the equator where the
instabilities have a lower phase speed. The energy analysis also shows
that these
waves
grow from both barotropic and baroclinic conversions.
Description:
This work was supported
by the Department of Com-
merce/NOAA
under grant NA56GP0026. One of the au-
thors (SM) was partially supported by a NASA Global Change Fellowship
NGT-30288. Another author (AB) was
supported by a UCAR Postdoctoral Fellowship
Description:
Published
Description:
29637-29661
Description:
4A. Clima e Oceani
Description:
JCR Journal
Description:
restricted
Keywords:
Ocean modeling
;
Equatorial Ocean
;
Tropical Instability Waves
;
Ocean wave generation
;
Ocean wave energetics
;
03. Hydrosphere::03.01. General::03.01.01. Analytical and numerical modeling
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
