Simulation of ENSO with a global atmospheric GCM coupled to a high-resolution, tropical Pacific ocean GCM
- Princeton Univ., NJ (United States)
A global atmospheric general circulation model (GCM) coupled to an oceanic GCM that is dynamically active only in the tropical Pacific simulates variability over a broad spectrum of frequencies. Of special interest is the simulation of a realistically irregular Southern Oscillation between warm El Nino and cold La Nino states with time scale of 5 years. The spatial structure is different in the eastern and western halves of the ocean basin. Sea surface temperature changes have their largest amplitude in the central and eastern tropical Pacific, but the low-frequency zonal wind fluctuations are displaced westward and are large over the western half of the basin. During El Nino the associated curl contributes to a pair of pronounced minima in thermocline depth, symmetrically about the equator in the west. In the east the deepening of the thermodine in response to the winds in the west has an approximate Gaussian shape centered on the equator. The low-frequency sea surface temperature and zonal wind anomalies wax and wane practically in place and in phase without significant zonal phase propagation. Thermocline depth variations have phase propagation, a property of the oceanic response to the quasi-periodic winds that force currents and excite a host of waves with periods near 5 years, This indicates that the ocean-atmosphere interactions that cause El Nino to develop at a certain time are countered and reversed by the delayed response of the ocean to earlier winds. Kelvin and Rossby waves cannot be identified in the low-frequency fluctuations of this model, but they are energetic at relatively short periods and are of vital importance to a quasi-resonant oceanic mode with a period near 7 months that is excited in the model. The similarities and differences between the results of this simulation and those with other models are discussed.
- OSTI ID:
- 6779236
- Journal Information:
- Journal of Climate; (United States), Vol. 5:4; ISSN 0894-8755
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ATMOSPHERIC CIRCULATION
GLOBAL ASPECTS
PACIFIC OCEAN
OCEANIC CIRCULATION
SOUTHERN OSCILLATION
GENERAL CIRCULATION MODELS
ANNUAL VARIATIONS
CURRENTS
FLUCTUATIONS
SIMULATION
SOLAR RADIATION
TROPICAL REGIONS
MATHEMATICAL MODELS
RADIATIONS
SEAS
STELLAR RADIATION
SURFACE WATERS
VARIATIONS
540110*
540310 - Environment
Aquatic- Basic Studies- (1990-)