Boyle, J. S., 1995a: Intercomparison of the spectral characteristics
of 200 hPa kinetic energy in AMIP GCM Simulations. PCMDI Report 23, Program
for Climate Model Diagnosis and Intercomparison, Lawrence Livermore National
Laboratory, 44 pp.
The 200 hPa kinetic energy budget terms are represented
by means of their spherical harmonic components for a number of AMIP simulations.
The data used are the monthly mean wind fields for 1979 to 1988 decadal
simulations. The budget terms are decomposed into the divergent and rotational
components. The comparison is limited to the lower wave numbers so as to
be within the nominal limits imposed by the models with the coarsest spatial
resolution. The results show considerable differences among the models.
The comparison is best for the rotational wind and degrades for the divergent
components, especially the conversion term. There is some ambiguity among
the models as to the sign of some terms at certain wave numbers. The models
tend to overestimate the Walker-type (east-west) divergent circulations
compared to the Hadley-type (north-south), as indicated by recent NMC and
ECMWF operational analyses. The intermodel differences are substantial
when viewed in light of the differences in the observational analyses and
ensemble differences for the ECMWF model. However, the median values of
all the models taken together are usually in fair agreement with observational
values. There is no obvious, systematic pattern of errors which can be
consistently attributed to specifics of the individual model horizontal
and vertical resolution, numerics or physical parameterizations.