Geoscience Reference
In-Depth Information
Figure 4.1
by Douglas
Mawson, published in London in 1915. (Credit: D.W. H.
Walton)
Cover of
The Home of the Blizzard
imbalance between different regions of our planet
before we can understand the processes responsible
for creating the unique climate of Antarctica.
Aside from a tiny fraction of energy gained from
geothermal processes within the Earth all of the
energy that drives the climate, and allows life to exist
on our planet, comes from the Sun in the form of
electromagnetic radiation. This radiation from the
sun is often called solar radiation and includes visible
light as well as forms of
which we cannot see,
such as ultraviolet (UV) radiation, which is
responsible for causing sunburn and skin cancer. All
objects on Earth, including the atmosphere, also emit
radiation. The range of
'
light
'
contained in this emitted radiation is referred to as
longwave radiation and is not visible to our eyes. If we consider a location at the edge
of the Earth
'
light
'
s atmosphere, on the fringe of outer space, the only way that energy can
be gained or lost by the atmosphere is by the gain of solar radiation or the loss of
longwave radiation. Solar radiation, having travelled from the Sun through the
vacuum of space, arrives at the top of the atmosphere. As this solar radiation passes
through the atmosphere it may be re
'
ected back out to space by clouds, dust, or even
the surface of the Earth. The remainder of this solar radiation is either absorbed by
the atmosphere or by the surface of the Earth. In either case, the atmosphere or the
surface of the Earth will be warmed when it absorbs solar radiation. Similarly,
longwave radiation emitted by the surface of the Earth, by clouds, and by the
atmosphere can pass upward through the atmosphere and eventually exit the
atmosphere to pass into the vacuum of space. It is the balance between the net
amount of solar radiation entering the atmosphere versus the amount of longwave
radiation leaving the atmosphere that determines whether a particular location on
the planet will warm or cool over time. As we will see the circulation of the
atmosphere serves to redistribute energy from areas with an excess of radiation gain
to areas with a net loss of radiation.
Over an entire year the amount of solar radiation entering the atmosphere
depends on the location. More solar radiation enters the atmosphere in the tropics
than in the polar regions. This spatial variation in the amount of solar radiation
reaching the top of the atmosphere has to do with the geometry of the Earth
'
s
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