MadSci Network: Environment & Ecology

Re: I (CFC's) are heavier than air how do they reach the ozone layer?

Date: Wed Feb 12 10:24:49 2003
Posted By: In Koo Kim, Grad student, Physical Chemistry, Harvard
Area of science: Environment & Ecology
ID: 1044316189.En

The air in the troposphere (<10km at middle latitudes) constitutes roughly
95%  of the total weight of the atmosphere.  Air in the troposphere is
relatively well mixed.  It takes roughly a few weeks for the breath you
exhale today to travel around the globe.  Additionally, because in the
troposphere, the temperature decreases with increasing altitude (look up
adiabatic lapse rate), there is good vertical mixing too (except in
winter).  Once CFCs are released at ground level, it's inert nature
combined with the overall good mixing in the troposphere results in a
dispersion of the gas on a global scale.  Additionally, diffusion aids
dispersing the CFC on a smaller scale.  The result is a distribution of the
CFC at a constant mixing ratio (e.g. parts per trillion, parts per
billion...) throughout the troposphere.  Now, as to the question of how the
CFC ever gets to the stratosphere, that is a big question in atmospheric
physics today.  One main theory is that in tropical areas such as Borneo,
the high amount of sunlight combined with air holding a lot of water,
results in vertical upwellings in turbulent storms.  The air is therby
"shot" through the tropopause (stratospher-troposphere boundary).  Another
theory holds that the tropopause elevation in the tropics (equatorial
region) allows for horizontal movement of air through the tropopause
without going through the barrior of vertical transport.  Either way,
stratosphere-troposphere exchange is not fully known and the area of study
is ripe for future scientists interested in the subject.

Current Queue | Current Queue for Environment & Ecology | Environment & Ecology archives

Try the links in the MadSci Library for more information on Environment & Ecology.

MadSci Home | Information | Search | Random Knowledge Generator | MadSci Archives | Mad Library | MAD Labs | MAD FAQs | Ask a ? | Join Us! | Help Support MadSci

MadSci Network,
© 1995-2003. All rights reserved.