Nigam, S., I. M. Held, and S. W. Lyons, 1988: Linear simulation of the stationary eddies in a GCM. Part II: The "mountain" model. Journal of the Atmospheric Sciences, 45(9), 1433-1452.

Abstract: The validity of linear stationary wave theory in accounting for the zonal asymmetries of the winter-averaged tropospheric circulation obtained in a general circulation model (GCM) is ascertained. The steady linear primitive equation model used towards this end has the same vertical and zonal resolution as the spectral GCM, but is finite-differenced in the meridional direction. It is linearized about a zonally symmetric basic state and forced by topography and 3-dimensional diabatic heating and transient flux convergence fields, all of which are taken from the GCM. As in Part I (in which we studied a GCM with a flat lower boundary), we obtained the best correspondence between the GCM and the linear solutions when when strong Rayleigh friction is included in the linear model not only near the surface, but in the interior of the tropical troposphere as well.

There is sufficient quantitative correspondence between the GCM and the linear solution to justify decomposing the linear simulation into parts forced by different processes, although in some regions, such as over North America, the simulation is unsatisfactory. Different fields give different impressions as to the relative importance of orography, heating, and transients. The eddy zonal vorticity field in the upper troposphere shows the orographic and thermal plus transient contributions to be nearly equal in amplitude, whereas the eddy meridional velocity field, dominated by shorter zonal scales, shows the orographic contribution to be decisively dominant. Although there is no systematic phase relationship between these two contributions, they are roughly in phase over the east Asian coast, where each of them is largest. They also contribute roughly equal amounts to the low level Siberian high.

Other findings are that (i) the 300 mb extratropical response to tropical forcing reaches 50 gpm over Alaska (given our frictional parameterization), which is smaller than the response to local thermal forcing, (ii) the responses to sensible heating and lower tropospheric thermal transients are strongly anticorrelated, and (iii) the circulation in the vicinity of the Andes in the GCM is not attributable to direct mechanical forcing by the mountains.