GFDL CM2.X - Model Construction

Model Construction

Atmosphere

The atmospheric component of the CM2.X models is a 24-level atmosphere run at a resolution of 2 degrees in the east-west and 2.5 degrees in the north-south direction. This resolution is sufficient to resolve the large mid-latitude cyclones responsible for weather variability. It is too coarse, however, to resolve processes such as hurricanes or intense thunderstorm outbreaks. The atmosphere includes a representation of radiative fluxes, mixing in the atmospheric boundary layer, representations of the impacts of stratus and cumulus clouds, a scheme for representing drag on upper level winds caused by gravity waves, changes in the spatial distribution of ozone, and the ability to represent the impact of multiple greenhouse gasses.

Ocean

The ocean component is a 50 level ocean, run at a resolution of 1 degree in the east-west direction and varying in the north-south direction from 1 degree in the polar regions to 1/3 of a degree along the equator. This resolution is sufficient to resolve the equatorial current system, but is too coarse to capture the highly energetic mesoscale eddies- whose advective and diffusive effects must be parameterized. Other key parameterizations include a free surface height which changes in response to evaporation, precipitation, and convergence of ocean currents, absorption of sunlight tied to observed chlorophyll concentrations, a representation of the oceanic mixed layer, inclusion of turbulence generated by tidal mixing on shelves and schemes allowing water from marginal seas such as the Red Sea and Baltic Sea to "mix" across narrow straits at their mouths.