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キーワード:
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要旨:
A detailed description of the fifth-generation ECHAM model is
presented. Compared to the previous version, ECHAM4, a number of
substantial changes have been introduced in both the numerics and
physics of the model. These include a flux-form semi-Lagrangian
transport scheme for positive definite variables like water components
and chemical tracers, a new longwave radiation scheme, separate
prognostic equations for cloud liquid water and cloud ice, a new cloud
microphysical scheme and a prognostic-statistical cloud cover
parameterization. The number of spectral intervals is increased in
both the longwave and shortwave part of the spectrum. Changes have
also been made in the representation of land surface processes,
including an implicit coupling between the surface and the atmosphere,
and in the representation of orographic drag forces. Also, a new
dataset of land surface parameters has been compiled for the new
model. On the other hand, horizontal and vertical diffusion, cumulus
convection and also the spectral dynamics remain essentially
unchanged.
