This
layer of Ozone filters (or blocks) harmful
UV
radiation, which could cause skin cancer.
Ozone is
also found in the air we breathe, in the
troposphere,
but this Ozone is `bad'; it can cause
damage to plants and lung tissues.
The figure below shows the structure of the lowest 50km of the atmosphere. It comprises of a number of different regions:
i) the `boundary layer' in
which we live, where chemical pollutants are emitted into the atmosphere
(mostly in the industrialised northern hemisphere). Ozone
is harmful at these levels;
ii) the `troposphere', where
chemicals will mix rapidly over a broad range of latitudes. Most aircraft
fly at these altitudes, and most weather systems live in this region;
iii) the `stratosphere',
the region which contains the protective ozone
layer. The picture here is typical of the southern hemisphere winter, e.g.
October, when in recent years very low ozone
levels have been observed over the Antarctic.
iv) the `mesosphere' and
beyond.
The brown arrows represent the circulation
in the atmosphere which takes things up in the tropics and down at the
poles.
The purple lines are surfaces of
constant potential temperature, along which chemicals will mix rapidly.
The red lines represent `barriers'
which inhibit transport between different parts of the atmosphere.
The back wavy lines represent disturbances, often coming
off mountains.