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Distribution of Temperature
Figure 9
gives the vertical distribution of temperature in the Earth's
atmosphere. This plot is a global average that overlooks spatial
(different locations on Earth) and temporal changes, which will be
discussed in the unit on atmospheric
structure and circulation. Notice
that the temperature decreases rather linearly from about 15°C at the
surface to about -55°C at an altitude of 10 km above the Earth's
surface. This region of the atmosphere, called the troposphere,
contains about three-fourths of the mass of the atmosphere, and its top
is called the tropopause. Above the tropopause is a 10-km thick region
of constant temperature, and above this layer the temperature increases
with height to about 0°C at a height of 50 km. This region above the
tropopause and below the stratopause at 50 km is called the
stratosphere. Ninety nine percent of the atmosphere is confined in the
lowest 30 km, and 99.9% is below 50 km. The extremely low density of
the atmosphere in the upper stratosphere and beyond give a different
meaning to the concept of temperature. The portion of the atmosphere
that is relevant to global change issues is the lowest 30 km.
