Geoscientific Model Development Discussions www.geosci-model-dev-discuss.net 1991-9611 1991-962X 2 1 2009 10.5194/gmdd-2-341-2009 http://www.geosci-model-dev-discuss.net/2/341/2009/ http://www.geosci-model-dev-discuss.net/2/341/2009/gmdd-2-341-2009.html http://www.geosci-model-dev-discuss.net/2/341/2009/gmdd-2-341-2009.pdf 341 383 2009-04-22 An Intermediate Complexity Climate Model (ICCM) based on the GFDL Flexible Modelling System R. Farneti riccardo.farneti@noaa.gov G. K. Vallis NOAA Geophysical Fluid Dynamics Laboratory, Princeton University, Forrestal Campus, 201 Forrestal Road, Princeton, NJ 08540, USA An intermediate complexity coupled ocean-atmosphere-land-ice model, based on the Geophysical Fluid Dynamics Laboratory (GFDL) Flexible Modelling System (FMS), has been developed to study mechanisms of ocean-atmosphere interactions and natural climate variability at interannual to interdecadal and longer time scales. The model uses the three-dimensional primitive equations for both ocean and atmosphere, but is simplified from a "state of the art" coupled model in two respects: it uses simplified physics and parameterisation schemes, especially in the atmosphere, and idealised geometry and geography. These simplifications provide considerable savings in computational expense and, perhaps more importantly, allow mechanisms to be investigated more cleanly and thoroughly than with a more elaborate model. For example, the model allows integrations of several millennia as well as broad parameter studies. For the ocean, the model uses the free surface primitive equations Modular Ocean Model (MOM) and the GFDL/FMS sea-ice model (SIS) is coupled to the oceanic grid. The atmospheric component consists of the FMS B-grid moist primitive equations atmospheric dynamical core with highly simplified physical parameterisations. 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