#
Simulation of Vertically-Propagating Waves in Comprehensive General
Circulation Models: Opportunities for Comparison With Observations

A number of important developments in observations of the middle
atmosphere
have been discussed at this meeting. Among the most exciting are the
display of
preliminary data from the Doppler radiometer instruments on UARS, the
development
of active optical methods for determining Doppler winds throughout the
entire height
range of the middle atmosphere, and the deployment of some nearly
identical MF
radars in an array extending over several hundred km. While such
developments are
extremely promising, the discussion at this meeting has highlighted the
limitations of
practical observations in producing a characterization of the full
three-dimensional,
time-dependent flow field in the middle atmosphere. Each method has
significant
limitations in terms of geographical and/or temporal coverage as well as
vertical and/
or horizontal resolution. In addition, there was much concern expressed
about the
magnitude of the discrepancies that have been observed when the various
radar and
optical methods are intercompared as directly as possible. These
problems all
suggest a role for three-dimensional numerical models in assessing and
interpreting
the available observations. One obvious use of the models is to
quantify the influence
of the spatial and temporal sampling inherent in the different
observation methods.
Another possible application is in four-dimensional data assimilation,
i.e. effectively
inserting observations as they become available into a GCM integration
(Rood et al.,
1989; Swinbank and O'Neill, 1994). A prerequisite for such applications
is a numerical
model that produces a reasonably realistic simulation of the middle
atmospheric wind
field, even at relatively short space and time scales. In this brief
paper the simulation
obtained by the GFDL "SKYHI" troposphere-stratosphere-mesosphere model
will be
reviewed with an emphasis on the vertically-propagating gravity waves
that account
for the variance over much of the atmospheric spectrum. The focus will
be on
examining the model results presented in formats similar to those
typically produced
from available observations.