Alex Megann, Adrian New, and Bablu Sinha, Southampton Oceanography
Centre,
Rainer Bleck, LANL, and Shan Sun, NASA/GISS
The CHIME (Coupled Hadley-Isopycnic Model Experiment) model comprises the Hadley Centre's atmosphere and ice models, coupled to HYCOM. CHIME is designed to be identical to the Hadley Centre's HadCM3 model except for its ocean component, allowing us to investigate the sensitivity of the climate to the choice of vertical coordinate in the ocean model.
The main 120-year integration of CHIME is now complete. Although the heat transport and meridional overturning in the two models are similar, CHIME shows several improvements compared with HadCM3. The path of the North Atlantic Current is more realistic than that in HadCM3, removing the heat flux errors in the subpolar gyre seen in the latter. Similarly, CHIME does not have the 4K cold bias seen in the North Pacific in HadCM3, the latter again associated with heat flux errors. However there is a 1.5 - 2-degree global surface warm bias in CHIME, not seen in HadCM3, which may well be remedied by tuning the cloud parameterisation.
Preliminary comparisons will also be made with the HYCOM/GISS coupled model control run.