The results of a synchronously coupled ocean-atmosphere GCM are presented in comparison with observation. The model consists of a six-layer oceanic GCM and a two-layer atmospheric GCM, each with a global horizontal resolution of four degrees latitude and five degrees longitude. Momentum, heat and moisture are exchanged at the ocean surface every hour as a function of the model's evolving sea-surface temperature and surface wind, with full diurnal and seasonal variations of solar radiation retained. In an extended interannual integration the coupled model simulates a climate which is similar in most respects to that produced by the uncoupled atmospheric GCM (with climatological sea-surface temperatures); a major exception is the coupled model's failure to simulate a realistic seasonal distribution of surface wind, sea-surface temperature and precipitation over the tropical Pacific Ocean. In January the coupled GCM simulates an El Niño-like collapse of the trades and the appearance of warm water across the equatorial Pacific; however, this occurs every year as part of the model's seasonal cycle, rather than as a sporadic interannual event. The major errors in the simulated sea-surface temperature itself are excessively cold water off the east coasts of Asia and North America, and excessively warm water off the western coasts of the tropical continents; these errors are evidently due to systematic errors in the simulated surface heat balance. These errors also cause a progressive loss of sea ice in the southern ocean, while the Arctic sea ice is realistically simulated. Further analysis of the results is underway in order to more fully understand the reasons for the model's behavior, and thereby to improve its ability to simulate large-scale ocean-atmosphere interaction.
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