Before the fires began in 1997, the El Nino and changing atmospheric patterns over the Indian Ocean, a pattern called the Indian Ocean Dipole, caused the ozone column to thicken, indicating that climatic factors play a major role. When scientists went back and looked at the 1980s El Nino events, they noticed the same behavior.
"However, we can detect no trend in smog ozone during the 1980s in the tropics, even though burning may have increased," said Thompson. "In some regions of the tropics, rising ozone precedes the burning period and in other regions, ozone levels don't rise as much as we would expect during the local burning season. Clearly, factors other than biomass burning exert a strong influence on tropical tropospheric ozone."
Since 1978, TOMS has eyed upper and lower level ozone in Earth's atmosphere. Since upper-level ozone in the stratosphere over the tropics is uniform, TOMS can subtract it out from its readings and calculate the smog in a "column" of atmosphere that stretches from the surface to the tropopause, more than 40,000 feet high.
A paper titled "Tropospheric Ozone and Biomass Burning," by Goddard's Anne Thompson and researchers at the University of Maryland; Science Systems and Applications, Inc.; and Hokkaido University of Japan, explaining the divergence of the pollutants, appears in the March 16 issue of Science.
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Contact: Cynthia O'Carroll
Cynthia.M.OCarroll.1@gsfc.nasa.gov
301-614-5563
NASA/Goddard Space Flight Center
14-Mar-2001