Geoscience Reference
In-Depth Information
8
General Circulation
Models
Introduction
Among the many acronyms used by scientists arguably 'GCM' is currently the best
recognized and most widely used, not only by meteorologists and hydrometeor-
ologists but also by other scientific disciplines, politicians and policymakers, and
by members of the public. Many non-experts think the acronym is shorthand for
'Global Climate Model' because it is widespread interest in global climate change
that has fostered its popularity. But the acronym predates this widespread interest
and in reality it is shorthand for
General Circulation Model
.
This chapter is written to provide an introduction to this aspect of present-day
atmospheric science for hydrometeorologists who will not necessarily become
experts in the specialized field of atmospheric modeling, but who need to be
familiar with the basic nature of GCMs and their strengths and shortcomings.
Because changes in the hydroclimate of the Earth are predicted, hydroclimatolo-
gists and hydrometeorologists need a basic understanding of the models used to
make such predictions.
What are General Circulation Models?
General Circulation Models are complex computer programs written to
describe how the air in the atmosphere moves, or circulates, around the globe.
To do this they include in their code the equations that describe the conserva-
tion and movement of momentum, energy, and the mass of atmospheric con-
stituents (including water vapor) which are discussed in later chapters. They
