7 Days Weather Outlook:
Z = Zulu = UTC (GT-Time Zone)
OZONE situation - by GOME (ERS-2)
Europe: Images of daily interpolated distribution of total column ozone
Ozone in the air overhead is measured in Dobson Units. The ozone hole is the area with
total column ozone below 220 Dobson Units. A reading of 100 Dobson Units means that if all
the ozone in the air above a point were brought down to sea-level pressure and cooled to
freezing it would form a layer 1 centimeter thick. At that scale a reading of 250 Dobson
Units translates to a layer about an inch thick.
Life on the surface of the Earth is protected from the harmful ultraviolet (UV) radiation
of the sun by the stratospheric ozone layer. Over the past several decades, synthetic
chemical compounds such as chlorofluorocarbons (CFCs) and halons were developed to provide
a new generation of refrigerants, insulating foams, fire retardants, and other products.
After extensive use of these man-made compounds, it was discovered that although they
remain in the lower atmosphere, they break down to release halogen radicals (e.g. chlorine,
bromine) in the stratosphere, destroying ozone via a catalytic cycle. Satellite and
ground-based observations confirm that losses of ozone are occurring seasonally, particularly
in the springtime polar vortex of the Antarctic stratosphere, leading to what is known as the
ozone hole. Also of concern is the more moderate ozone depletion observed in mid-latitudes,
where a large portion of the Earth's population resides. Decreases in atmospheric ozone will
increase the amount of harmful ground-level UV-B radiation. In order to map and monitor such
problematic phenomena as ozone destruction or global climate change, global long-term measurements
of atmospheric trace gases are needed. Satellites can make a significant contribution.
