Geography Reference
In-Depth Information
CHAPTER 7
Atmospheric Oscillations:
Linear Perturbation Theory
Chapter 13 discusses numerical techniques for solving the equations governing
large-scale atmospheric motions. If the objective is to produce an accurate fore-
cast of the circulation at some future time, a detailed numerical model based on
the primitive equations and including processes such as latent heating, radiative
transfer, and boundary layer drag should produce the best results. However, the
inherent complexity of such a model generally precludes any simple interpretation
of the physical processes that produce the predicted circulation. If we wish to gain
physical insight into the fundamental nature of atmospheric motions, it is helpful to
employ simplified models in which certain processes are omitted and compare the
results with those of more complete models. This is, of course, just what was done
in deriving the quasi-geostrophic model. However, the quasi-geostrophic potential
vorticity equation is still a complicated nonlinear equation that must be solved
numerically. It is difficult to gain an appreciation for the processes that produce
the wave-like character observed in many meteorological disturbances through the
study of numerical integrations alone.
This chapter discusses the
perturbation method
, a simple technique that is useful
for qualitative analysis of atmospheric waves. We then use this method to examine
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