CLIMATE SIMULATIONS WITH THE GLOBAL COUPLED ATMOSPHERE OCEAN MODEL ECHAM2 OPYC .1. PRESENT-DAY CLIMATE AND ENSO EVENTS/

In this study the global coupled atmosphere-ocean general circulation model ECHAM2/OPYC and its performance in simulating the present-day cl imate is presented. The model consists of the T21-spectral atmosphere general circulation model ECHAM2 and the ocean general circulation mod el OPYC with a resolution corresponding to a T42 Gaussian grid, with i ncreasing resolution towards the equator. The sea-ice is represented b y a dynamic thermodynamic sea-ice model with theology. Both models are coupled using the flux correction technique. With the coupled model E CHAM2/OPYC a 210-year integration under present-day greenhouse gas con ditions has been performed. The coupled model simulates a realistic me an climate state, which is close to the observations. The model genera tes several ENSO events without external forcing. Using traditional an d advanced (POP-technique) methods these ENSO events have been analyze d. The results are consistent with the ''delayed action oscillator'' t heory. The model simulates both a tropical and an extra-tropical respo nse to ENSO, which are in good agreement with observations.