Waveguide Effects in Planetary Wave Propagation
and Quasi-geostrophic Approximation Applicability

B. E. Stepanov and E. I. Ginzburg

Novosibirsk State Engineering University, pr. K. Marksa 20, Novosibirsk, 630092 Russia

Received December 22, 1997; in final form, April 20, 1998

Abstract—It is shown that a global numerical model reproduces waveguide effects revealed previously in the
propagation of stationary planetary waves by using the quasi-geostrophic approximation. A comparison of the
results of global and hemispherical calculations with those of the quasi-geostrophic model shows that, for a cor-
rect estimation of the variability of planetary waves in the middle atmosphere, it is necessary to start from the
complete system of equations, because the use of the quasi-geostrophic approximation may lead to a significant
distortion of actual wave structures, so that the amplitudes of disturbances may be several times greater or
smaller than the corresponding global values. The global index of refraction is introduced for a one-level model.
It is noted that the method of matrix factorization over any direction may be used for global calculations of plan-
etary waves.

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