Introduction - The Global Climate System: Patterns, Processes, and Teleconnections - page 4

Background Box 1.1
Energy flow representation
The exchanges and flows associated with energy inputs into the Earth-atmosphere
system is represented by a series of symbolic equations. Use of the equations permits
easy calculation once values are input.
Shortwave solar radiation (K # ) reaching the surface is made up of the vertical
radiation (S) and diffuse radiation (D):
K #¼ S þ D
Some of the energy is reflected back to space (K " ) so that net shortwave radiation
(K*) is the difference between the two:
K* ¼ K # K "
Net longwave, terrestrial radiation (L*) comprises downward atmospheric
radiation (L # ) less upward terrestrial radiation (L " ):
L* ¼ L # L "
The amount of energy available at any surface is thus the sum of K* and L*. This is
net all-wave radiation (Q*):
Q* ¼ K* þ L*
which may also be given as
Q* ¼ð K # K "Þ þ ð L # L "Þ
Q* may be positive or negative.
High positive values will occur during high sun periods when K # is at its
maximum and atmospheric radiation, L # , exceeds outgoing radiation, L " .
Negative values require outgoing values to be greater than incoming. This
happens, for example, on clear nights when L " is larger than other values.
On a long-term basis, Q* will vary with latitude and surface type.
The heat budget
Consider a column of the Earth's surface extending down to where vertical heat
exchange no longer occurs (Figure 1.3 ). The net rate (G) at which heat in this column
changes depends upon the following:
Net radiation (K " K # ) þ (L " L # )
Latent heat transfer (LE)
Sensible heat transfer (H)
Horizontal heat transfer (S)