The dynamical processes which maintain atmospheric disturbances
in regions of strong wintertime variability of the northern hemisphere
are examined using data from a GCM simulation. Time series of the
dependent variables and diabatic heating components from 10 Northern
Hemisphere winters simulated by the Oregon State University two-level
GCM are used. Variance and covariance analyses are performed to
determine the geographical distribution of the intensities and transport
properties of high-frequency (periods between 2.5 and 10 days)
and low-frequency (periods between 10 days and a season) eddies.
These are compared with existing observations and the discrepancies
are discussed in terms of their dynamical consistency with the
time-mean circulation.
The energetics of high-frequency and low-frequency eddies are
studied. It is found that the behavior of high-frequency eddies is
consistent with baroclinic instability theory. Low-frequency eddies
appear to be maintained mainly by a high-latitude baroclinic energy
cycle. Energy conversions characteristic of barotropic processes are
also significant at jet-stream-latitudes. The process of wave-energy
dispersion is found to be an important factor governing the geographical
distribution of low-frequency activity at middle latitudes.
The nature of the systems causing low-frequency variability over
the North Pacific Ocean is examined by applying complex EOF analysis
to the time series of geopotential height anomalies. The first eigenmode
of this analysis describes a wave of planetary scale extending
from northeastern Asia to the Gulf of Mexico across the North Pacific
basin. While the phase of this wave retrogrades along the continental
borders of the ocean basin, energy propagates in the opposite direction
and penetrates as far as the central North Atlantic. The dynamical
characteristics of this disturbance are examined by complex covariance
analysis between the first mode's principal component and the
dependent-variable fields. It is found that the disturbance grows
mainly through baroclinic processes with some contribution from barotropic
processes.
On the basis of these results it is proposed that the observed
differences between the high- and low-frequency disturbances result
from their being generated in different geographical regions where
sphericity and the properties of the stationary flow cause baroclinic
growth of structurally different modes. / Graduation date: 1985
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29233 |
| Date | 13 December 1984 |
| Creators | Kushnir, Yochanan |
| Contributors | Esbensen, Steven K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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