The Low-Resolution CCSM3

Abstract The low-resolution fully coupled configuration of the Community Climate System Model version 3 (CCSM3) is described and evaluated. In this most economical configuration, an ocean at nominal 3° resolution is coupled to an atmosphere model at T31 resolution. There are climate biases associated with the relatively coarse grids, yet the coupled solution remains comparable to higher-resolution CCSM3 results. There are marked improvements in the new solution compared to the low-resolution configuration of CCSM2. In particular, the CCSM3 simulation maintains a robust meridional overturning circulation in the ocean, and it generates more realistic El Niño variability. The improved ocean solution was achieved with no increase in computational cost by redistributing deep ocean and midlatitude resolution into the upper ocean and the key water formation regions of the North Atlantic, respectively. Given its significantly lower resource demands compared to higher resolutions, this configuration shows promise for studies of paleoclimate and other applications requiring long, equilibrated solutions.