Stratospheric and Ground Ozone
Name: Igor L.
Is there any real connection between stratospheric ozone
and ground level one? I mean connection in trends. Now we have negative
trend in column ozone. What trend should be in ground ozone from the
theoretical point of view?
Ground-level ozone is a photochemical reaction product of air oxygen,
nitrogen oxide catalysts, and hydrocarbons. The nitrogen oxides and
hydrocarbons are predominantly provided by human activity, specifically car
and diesel exhaust. Stratospheric ("ozone layer") ozone is also a
photochemical reaction product, but its creation does not require
hydrocarbons or man-made nitrogen oxides. (The nitrogen oxides in the
stratosphere occur naturally.) The increased destruction of stratospheric
ozone observed recently is attributed to volatile man-made
chlorine-containing compounds that rise to the stratosphere.
So increased ground-level ozone and decreased stratospheric ozone are both
effects of man-made pollution. Different pollutants lead to the two
different effects. The different ozone levels are connected to the extent
that the pollutant trends are connected.
Richard E. Barrans Jr., Ph.D.
PG Research Foundation
Under some meteorological conditions, such as
thunderstorm convection, which displaces much
air vertically, down as well as up, ozone from
the stratosphere can be brought to the surface.
However, virtually all of the ozone near the
surface is created photo-chemically, aided by
man's pollution. The only other strong connection between
the upper and lower parts of the atmosphere are the
CFCs that are transported slowly into the stratosphere
where they cause ozone depletion, as is easily seen
over Antarctica (because of it's unique weather patterns).
Because of the effects of pollution, ozone had been
increasing near the surface, while ozone depletion was
taking place in the stratosphere. The increasing trend
near the surface has been reversed in the past 10 years
in the USA as a result of emission controls that have reduced
ozone "precursors" like nitrogen oxides. Most of the
"non-attainment" areas (where ozone was higher than
EPA standards) have met the standards recently. More effective
controls on power plant emissions that are presently
being implemented will continue to help in this effort.
Further reductions through cleaner automobiles and more
efficient home heating would help even more, although it will
be quite costly. All of this is wonderful for our country,
but most of the world does not share our enthusiasm for
and dedication towards cleaning the environment. The rest
of the world needs to get on the bandwagon for future
improvements to occur globally.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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Update: June 2012