Using a linear quasi-geostrophic model of large scale spiraling flow and vertical density
gradient in the eastern North Pacific, we evaluate the complex dispersion relationships
for quasi-geostrophic waves. Our calculations indicate that the geostrophic circulation
of the eastern North Pacific can locally convert potential energy to mesoscale
kinetic energy on a scale comparable to the observed space and time scale and should
be a source of eddy energy, distant from the eddies spawned by the Kuroshio and near
the topographic features. But the local growth rates by linear stability analysis do not
relate to the observed features of eddy kinetic energy in the eastern ocean; eddy kinetic
energy increases to the south and has a maximum in the subtropical region.
The non-linear baroclinic instability is analyzed using a three-layer quasi-geostrophic
numerical model. Three experiments with different idealized initial mean
flow are performed. Local energetics are calculated to highlight the difference between
the southward return flow and westward return flow regions. It is found that the
boundary flux of mean to eddy kinetic energy conversion is the main differences
between two regions: it is large in the westward return flow region but is small in the
southward return flow region. Two waves with different characteristics are found: the
short waves (periods of 120 days), that propagate to the west and form several wave
trains parallel to the southern boundary, and the long waves (periods of 200 days),
that propagate to the south-west. These two waves are remarkably similar to the
measurements of open ocean eddies at 28°N and 152°W. It is shown that there are high
eddy activities in the southward return flow regions by influxes of eddies from other
areas, but the southward return flow region is vacant in eddies by outflows of the westward
and south-westward propagating waves. / Graduation date: 1987
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27794 |
| Date | 04 May 1987 |
| Creators | Lee, Dong-kyu |
| Contributors | Niiler, Peter P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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