A numerical investigation of the long-term transient behavior in a coupled atmosphere-ocean model.

Abstract

A two-level, quasi-geos trophic atmospheric model on a mid-latitude ß-plane with a single wave in the x-direction was coupled with a three level primitive equation ocean model through the exchange of sensible heat and momentum to investigate the effect of the ocean circulation on transients in the atmospheric circulation and vice versa. A long-term (79 years) simulation of the atmosphere-ocean system was carried out. The experiment was conducted in three phases that consisted of integrating the combined, the ocean-only and the atmosphere-only model equations. The combined model produced realistic patterns of both atmospheric and oceanic circulations. Energy studies of the atmosphere were completed with the results comparing favorably with the existing knowledge of the energy balance in the real atmosphere. Data were retained at selected points on a daily basis and spectrally analyzed for a simulated six year period. Transients with periods on the order of one and two months appeared in the spectra of both atmospheric and oceanic variables from the combined model. These transients were not observed in the ocean-only or atmosphere-only phases of the experiment, and are attributed to the interaction occur ring in the combined model.