A Comparison of the Atmospheric Circulations Simulated by the CCM3 and
CSM1
Journal of Climate: Vol.11, No. 6, pp.1327-1341.
A Comparison of the Atmospheric Circulations Simulated by the
CCM3 and CSM1
Byron A. Boville and James W. Hurrell
National Center for Atmospheric Research, Boulder, Colorado
(Manuscript received 7 May 1997, in final form 24 September 1997)
The atmospheric state simulated by the National Center for Atmospheric Research
(NCAR) Community Climate Model, version 3 (CCM3), is compared to that simulated
by the NCAR Climate System Model, version 1 (CSM1). CCM3 is an atmospheric
general circulation model that uses specified sea surface temperatures (SSTs)
for a lower boundary condition. Observed monthly mean SSTs for 1979-93 were
used in the present study. CSM1 is a coupled general circulation model in which
the SSTs are determined as part of the simulation and CCM3 serves as the
atmospheric component. It is found that the differences between CCM3 and CSM1
are quite small in most measures of the atmospheric circulation, consistent
with the accurate and drift-free simulation of the SSTs in the coupled model.
There are substantial temperature differences near the surface in the Arctic
and over the ocean around Antarctica, resulting from different sea-ice
distributions. The tropical precipitation also has significant differences,
although neither simulation is clearly better and the errors in the two
simulations tend to have opposite signs with respect to observations. In
response to the change in latent heat release the tropical divergent
circulation changes significantly. Middle- and high-latitude circulation
changes are modest, occurring mostly in winter in association with the
sea-ice changes.
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Hongjun Zhang:
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