Experiment with a Simple Ocean-Atmosphere Climate Model: The Role of the Ocean in the Global Climate

Abstract

A study of the seasonal variation of the climatic states of the atmosphere and the ocean is made using a coupled atmosphere-ocean model. The ?domain-averaged? nature of the model enables the inclusion of effects due to continent-ocean-ice distribution in a quasi-two-dimensional framework. While the atmosphere is described by simplified ?domain-average? primitive equations, the ocean is represented as simple advective mixed layer. Large-scale circulation and upwelling in the ocean are modeled in terms of a wind-driven and a thermally driven component. Integration is carried out for the coupled model until a repeatable annual cycle is observed in the mean climatic states. Results of the experiment show that large differences in the time scale and amplitude of the response exist between the land and ocean domains. Features of the mean atmospheric circulation such as the Hadley cell, the Ferrel cell, tropical easterly jet and monsoon transition are well simulated. In the model ocean the domain-averaged spatial and temporal response of sea surface temperature and mixed layer depth are simulated fairly realistically. The large-scale circulation in the ocean shows some interesting features such as the gyre circulation, the western boundary transports, and a decrease in sea surface temperature in eastern and equatorial oceans as a result of oceanic upwelling. In the overall heat budget of the combined system, the ocean is found to dominate in energy storage. Between 20 and 30°S, the maximum oceanic poleward heat transport is computed in February and March and is as large as or larger than the corresponding atmospheric heat transport at the same latitudes.