Environmental Engineering Reference
In-Depth Information
average annual shortwave radiation reaching the ground, it is appreciably different
(Figure 3.2). The general impression of the map is of a decrease in energy input towards
the poles, with local anomalies. Most of these anomalies are caused by the
Figure 3.4
Contrasting diurnal temperature variations on
cloudy and clear days at Sheffield, South Yorkshire. Cloudy
weather prevailed for the first three days, giving a small
diurnal temperature range. As the skies cleared later in the
week, daytime temperatures increased but night-time
temperatures became lower. There is some indication of a
slight progressive warming of both day and night
temperatures as a result of the storage of solar energy.
THE GREENHOUSE EFFECT
key concepts
The property of the atmosphere that allows the transmission of sunlight, but acts as a
partial barrier to the loss of heat from the surface, has been called the
greenhouse effect
because of its analogy with the greenhouse, which appears to produce warming by a
similar process. Subsequent work has shown that greenhouses are warmed as much by
the removal of wind as by any radiational effect but the name of the effect has remained.
Without this natural greenhouse effect Earth's equilibrium temperature would be about -
19° C and the planet would be almost uninhabitable. We can work this figure out from
the amount of long-wave radiation which is lost by the planet and now measured by the
orbiting satellites.
