Climate of extremes - Antarctica: Global Science from a Frozen Continent - page 113

Figure 4.10 Winter (red line) and

summer (green line) temperature
pro les over the South Pole compared
with the typical temperature pro le
found in mid-latitudes. The winter
pro le shows a strong surface
inversion where temperatures increase
rapidly just above the surface.

Temperature Profile

35

30

25

20

Standard Atmosphere

South Pole - 21 June 2010

15

South Pole - 21 Dec 2010

10

5

0

-100 -80 -60 -40 -20 0 20

Tem perature (deg C)

locations in the Arctic provides one explanation as to why the Antarctic is so
much colder than the Arctic. The topography of the Antarctic continent, which
is characterised by a high plateau over much of the interior, with steeply sloping
terrain near the edge of the continent, is also important in shaping the winds that
are a de ning characteristic of the Antarctic climate.

The extremely cold temperatures are not the only unique aspect of temperature
in the Antarctic. Temperature normally decreases with increasing altitude in the
troposphere and this decrease in temperature is due to the fact that the surface
of the Earth is strongly warmed by absorbed sunlight. Since only a limited amount
of sunlight reaches the surface of the Antarctic and much of it, more than 80% in
some locations, is re ected back out to space, there is very little warming of the

Antarctic surface. In addition the surface is emitting longwave radiation, which
leads to a net loss of energy from the ground and cooling of the surface. In the
Antarctic the ground then serves to cool the air in contact with it rather than
to warm the air as occurs in more temperate locations.
The situation described above occurs during the Antarctic summer months. In
the winter, no solar radiation reaches the ground in the Antarctic and the cooling of the
surface due to longwave radiation emission is even greater than in summer. As a result
the air in contact with the cold surface also becomes very cold, and a temperature
inversion develops. As one moves up through the Antarctic atmosphere, away from the
cold ground, temperatures increase. This temperature inversion is found in the lowest
several hundred metres of the atmosphere, and is a characteristic of the Antarctic
climate that persists year-round. The inversion is strongest, that is the temperature
increases most rapidly with height, during the winter when the ground is losing the most
energy and is weaker in the summer when there is some solar radiation available to offset
the longwave radiation loss. In the winter it is possible for the temperature to increase
25 C or more from the ground to an altitude of several hundred metres. Much of this
temperature increase occurs close to the ground and it is possible that if you were