AN EXAMINATION OF INTERNALLY GENERATED VARIABILITY IN LONG CLIMATE SIMULATIONS

General circulation model experiments designed to estimate the magnitu de and structure of internally generated variability and to help under stand the mechanisms underlying this variability are described. The ex periments consist: of three multi-century integrations of a rhomboidal 15, 9 level, version of the Center for Ocean-Land-Atmosphere Studies atmospheric general circulation model: a run with fixed sea surface te mperatures and equinox solar radiation, a run with seasonally varying climatological sea surface temperatures and seasonally varying solar f orcing, and a run with seasonally varying solar forcing in which the s tate of the ocean is predicted by a 3 degrees by 3 degrees, 16 vertica l level, nearly global domain version of the Geophysical Fluid Dynamic s Laboratory Modular Ocean Model. No flux correction is used in the co upled model integration. Selected surface fields of the three runs are compared to each other as well as to the observed climate. Statistica l properties of variability on interannual time scales are compared be tween the runs. Evidence is presented that climate time scale variabil ity in the simulations is produced by random weather time scale forcin g due to the integrating effect of elements of the system with long me mories. The importance of ocean variability for land climate variabili ty is demonstrated and attributed to both the memory effect and couple d atmosphere-ocean instability.