Parallel Climate Model (PCM) Control and 1%/year CO2
Simulatons with a 2/3o Ocean Model and a 27 km Dynamical Sea Ice
Model
Warren M. Washington, Gerald A. Meehl, Thomas W. Bettge, Anthony P.
Craig, Warren G. Strand, Julie Arblaster, Vincent B. Wayland and Rodney James
National Center for Atmospheric Research, Boulder, Colorado
John W. Weatherly
U.S. Army Cold Regions Research and Engineering Laboratory (CRREL)
Albert J. Semtner, Jr and Yuxia Zhang
U.S. Naval Postgraduate School (NPS)
The Department of Energy (DOE) supported Parallel Climate Model (PCM) makes use
of the NCAR Community Climate Model (CCM3) and Land Surface Model (LSM) for the
atmospheric and land surface components, respectively, the DOE Los Alamos
National Laboratory Parallel Ocean Program (POP) for the ocean component, and
the Naval Postgraduate School sea ice model. The PCM executes on several
distributed and shared memory computer systems. Computer performance information
is included. The coupling method is similar to that used in the NCAR Climate
System Model (CSM) in that a flux coupler ties the components together, with
interpolations between the different grids of the component models. Flux
adjustments or corrections are not used in the PCM. The ocean component has
2/3o average horizontal grid spacing with 32 vertical levels and a
free surface that allows calculation of sea level changes. Near the equator, the
grid spacing is approximately 1/2o in latitude to better capture the
ocean equatorial dynamics. The North Pole is rotated over northern North America
thus producing resolution smaller than 2/3o in the North Atlantic
where the sinking part of the world conveyor circulation largely takes place.
Because this ocean model component does not have a computational point at the
North Pole, the Arctic Ocean circulation systems are more realistic and similar
to the observed. The elastic viscous plastic sea ice model has a grid spacing of
27 km to represent small-scale features such as ice transport through the
Canadian Archipelago and the East Greenland current region.
Results from a 300 year present-day coupled climate control simulation are
presented, as well as for a transient 1% per year CO2 increase
experiment which shows a global warming of 1.27oC for a 10 year
average at the doubling point of CO2 and 2.89oC at the
quadrupling point. There is a gradual warming beyond the doubling and
quadrupling points. A 0.5% per year CO2 increase experiment is also
performed showing a global warming of 1.5oC and a similar warming
pattern to the doubling experiment. Globally averaged sea level rise at the time
of CO2 doubling is approximately 15 cm and at the time of quadrupling
it is 23 cm. Some of the regional sea level changes are larger and reflect the
adjustments in the temperature, salinity, internal ocean dynamics, surface heat
flux, and wind stress on the ocean. El Niño and La Niña events in the
tropical Pacific show approximately the observed frequency distribution and
amplitude, which leads to near observed levels of variability on interannual
time scales.
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Hongjun Zhang:
zhangho@ucar.edu