CMI's goal is to develop an efficient coupled climate model that can be integrated over many thousands of years for the purpose of long-term climate studies.

Recognizing that the atmosphere and ocean are governed by equations that are isomorphic to one another, we have built a coupled climate model based on a single dynamical core - MITgcm. Separate atmospheric and oceanic models are rendered by use of appropriate physics overlaid on the dynamics.

Features of our approach include:

	Isomorphism The dynamical core of MITgcm exploits the isomorphism between the equations of motion and boundary conditions that govern the atmosphere and ocean, in pressure (p) and height coordinates (z) respectively.
	Finite Volumes The vertical coordinate (generic name "r") is scaled by the total fluid column thickness yielding a modified r* vertical coordinate analogous to the atmospheric Eta coordinate. Combined with the finite volume method and a partial cell representation of topography, the method remains accurate near steep topography.
	Cubed Sphere An expanded cubic grid provides a global coverage of the sphere with a relatively uniform resolution (2.8 degree at the equator) and is used in both atmosphere and ocean, thus avoiding the problem of convergence or meridians as the pole is approached. Careful discretization allows one to accurately treat the whole domain, including the eight singular points at the corner of the cube.
	Single Processor Coupling interface The use of the same horizontal grid simplifies the coupling procedure, and conservation properties of the coupled model. The 2 components exchange fluxes and surface fields through a single processor coupling interface, using MPI.
	Packaged Physics An atmospheric physics package of intermediate complexity (called SPEEDY, Molteni, 2003) enable extended (100's to 1000's of years) integrations to be carried out. Although highly idealized the simplified atmospheric model captures many realistic features of atmospheric circulation. Other components include a simple land model (2 levels), an instantaneous runoff scheme and thermodynamic sea-ice.
	Compute-Cluster-Ready-Efficiency The model runs efficiently on a local PC cluster enabling thousands of years of  integration to be carried out in days.