Nigam, S., I. M. Held, and S. W. Lyons, 1986: Linear simulation of the stationary eddies in a general circulation model. Part I: The no-mountain
model. Journal of the Atmospheric Sciences, 43 (23), 2944-2961.
Abstract: The quantitative validity of linear stationary wave theory is examined
by comparing the results from a linear primitive equation model on the sphere
with the stationary eddies produced by a general circulation model (GCM).
The GCM simulated has a flat lower boundary, so that the stationary eddies
can be thought of as forced by heating (sensible, latent and radiative)
and time-averaged transient eddy flux convergences. Orographic forcing is
examined in the second part of this study. The distribution of the diabatic
heating and transient eddy flux convergences and the zonally symmetric basic
state are taken directly from the GCM's climatology for Northern winter
(DJF). Strong Rayleigh friction is included in the linear model wherever
the zonal mean wind is amall, as well as near the surface.
The linear model is found to simulate the stationary eddy pattern of the
GCM with considerable skill in both midlatitudes and the tropics. Some deficiencies
include the inaccurate simulation of the upper tropospheric geopotential
over North America and distortion of the wind field near the low-level zero-wind
line in the subtropics. Decomposition of the linear solution shows that
1) the extratropical upper tropospheric eddy pattern generated by tropical
forcing is significant but smaller than that due to extratropical forcing,
2) the upper-level extratropical pattern deteriorates somewhat when forcing
by transients is removed, while the low-level pattern deteriorates dramatically
and 3) there is considerable compensation between the effects of low-level
thermal transients and extratropical sensible heating, to the point that
we argue that this decomposition is not physically meaningful. The sensitivity
of the results to the Rayleigh friction formulation is discussed, as is
the effect of replacing the transients with thermal damping.