Geoscience Reference
In-Depth Information
Numerical models of the general
circulation, climate and weather
prediction
T. N. Chase and R. G. Barry
Learning objectives
When you have read this chapter you will:
Know the basic features of atmospheric general circulation models (GCMs),
Understand how simulations of the atmospheric circulation and its characteristics are performed,
Be familiar with the basic approaches to weather forecasting on different time scales.
Fundamental changes in our understanding of the
complex behaviour of the atmosphere and climate
processes have been obtained over the past three decades
through the development and application of numerical
climate and weather models. Numerical models simply
use mathematical relationships to describe physical
processes. There are many forms of climate and weather
models ranging from simple point energy balance
approaches to three-dimensional general circulation
models (GCMs) which attempt to model all the com-
plexities of the earth climate system. We discuss in more
detail the GCM in its various forms which is used
to simulate both climate and weather for day-to-day
forecasting.
A FUNDAMENTALS OF THE GCM
In the GCM, all dynamic and thermodynamic processes
and the radiative and mass exchanges that have been
treated in Chapters 2 to 7 are modelled using five basic
sets of equations. The basic equations describing the
atmosphere are:
1
The three dimensional equations of motion (i.e.
conservation of momentum; see Chapter 6A,B).
2
The equation of continuity (i.e. conservation of mass
or the hydrodynamic equation, p. 118).
3
The equation of continuity for atmospheric water
vapour (i.e. conservation of water vapour; see
Chapter 4).
4
The equation of energy conservation (i.e. the ther-
modynamic equation derived from the first law of
thermodynamics, see Chapter 7C).
