For the purpose of investigating the fundamental nature of the
interannual oscillation observed in the tropical Pacific in conjunction with
El Nino/Southern Oscillation (ENSO), the Comprehensive Ocean
Atmosphere Data Set was analyzed. Based upon this analysis, an
"intermediate" tropical atmosphere-ocean coupled model was developed.
For reason of their particular importance to atmosphere-ocean interactions,
moisture processes such as condensation-convergence, evaporation-sea
surface temperature and evaporation-wind feedbacks were given special
emphasis in both the data analysis and modeling processes. The
atmospheric component of the model is based on the first baroclinic mode,
which is driven by the atmospheric internal heating. The oceanic model
consists of two layers with an imbedded oceanic mixed-layer, by which SST
is predicted.
The present study has demonstrated that despite the structural
simplicity of the oceanic model, it is capable of simulating mean oceanic
circulation. In preparation for coupling, individual models were first tested
with the use of appropriate time-dependent boundary conditions specified
from the composite ENSO data. Both model simulations reproduced the
major features associated with the ENSO events.
Coupling was performed following the imposition of wind stress
anomalies over the western Pacific for a given time period and the removal
of all external forcing for a period of eight years thereafter. The coupled
responses simulated during the the first two-year period provided
reasonable simulations of the following ENSO-like features: the appearance
of warm sea-surface temperature anomalies in the central Pacific,
deepening/shallowing of mixed-layers in the eastern/western Pacific,
weakening of the trades in the central Pacific, strengthening/weakening of
the North Equatorial Counter Current/South Equatorial Currents, and
enhanced convective activities around the dateline. The long-term coupled
integration showed a pattern of interannual oscillation over a period of
approximately three years.
The results obtained from this coupling study have illustrated (1) that
the necessary condition for the interannual oscillation is the interaction
between the atmosphere and the ocean and (2) that it is likely that oceanic
wave dynamics plays a crucial role in the determination of the growth and
decay of ENSO events. / Graduation date: 1991
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29066 |
| Date | 23 August 1990 |
| Creators | Ahn, Joong Bae |
| Contributors | Han, Young-June |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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