TECHNIQUES FOR ASYNCHRONOUS AND PERIODICALLY SYNCHRONOUS COUPLING OF ATMOSPHERE AND OCEAN MODELS .1. GENERAL STRATEGY AND APPLICATION TO THE CYCLE-STATIONARY CASE

Asynchronous and periodically-synchronous schemes for coupling atmosph ere and ocean models are presented. The performance of the schemes is tested by simulating the climatic response to a step function forcing and to a gradually increasing forcing with a simple zero-dimensional n on-linear energy balance model. Both the initial transient response an d the asymptotic approach of the equilibrium state are studied. If no annual cycle is allowed the asynchronous coupling technique proves to be a suitable tool. However, if the annual cycle is retained, the peri odically synchronous coupling technique reproduces the results of the synchronously coupled runs with smaller bias. In this case it is impor tant that the total length of one synchronous period and one ocean onl y period is not a multiple of 6 months.