the situation, the relative vorticity is decreasing
downstream. We may state that surface pressure falls
where relative vorticity decreases downstream in the
upper troposphere, or where advection of more cyclonic
vorticity takes place aloft. The converse of this is in the
case of convergence aloft.
SUMMARY
In this chapter we expanded on the subjects of
convergence, divergence, and vorticity, which were first
presented in the AG2 manual, volume 1. Our discussion
first dealt with convergence and divergence as simple
motions. The dynamics of convergent and divergent
flow was covered, along with a discussion of wind
directional shear and wind speed shear. Convergence
and divergence as complex motions were then
presented. Rules of thumb on convergence and
divergence relative to surface and upper air features
were covered. The last portion of the chapter dealt with
vorticity. Definitions of relative vorticity and absolute
vorticity were covered. Vorticity effects on weather
processes was the last topic of discussion.
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