Jan 29, 2010

LIS science: atmospheric chemistry

Atmospheric chemistry

Sometimes you think you can smell lightning. Actually, what you smell is the ozone produced by lightning. (Ozone is three oxygen molecules - O3 - bound together. It breaks down into a molecule - O2 - plus an atom of free oxygen - O - that reacts with anything handy (including nerve endings in your nose.)

The electrical current and intense temperatures produced by a lightning stroke create a mini-chemical factory where ordinary oxygen (O2) and nitrogen (N2) molecules are chopped into atoms and then into ions.

Most of these atoms reform as ordinary oxygen and nitrogen, but a significant number form nitrous oxide compounds (NO, NO2, and NOx). In the 1983 Global Troposphere Experiment, aircraft sampled the air inside two cumulonimbus clouds and found that the levels of NO had risen 50-fold, from 20 to 1000 parts per trillion.

If this proves to be true of all thunderclouds, then lightning - especially cloud-to-cloud flashes closer to the stratosphere - could be a significant producer of chemicals that deplete the Earth's protective ozone layer.

The efficiency of lighting in producing these chemicals is unknown. Once the conversion rate is pinned down by other studies, then data from LIS will be crucial in converting the efficiency into a good estimate of the actual production of ozone-depleting and other chemicals.

Back to the Lighting Imaging Sensor story.