Mapping the quantity of these chemicals in the atmosphere, where they're located, where they come from, where they're going and what they're doing is vital to understanding weather and climate, air quality, pollution levels and the health of the ozone layer that protects the Earth's surface from the sun's damaging ultraviolet radiation.

The scientific and technical challenges of measuring these chemicals and understanding their role in the atmosphere are as enormous as the atmosphere itself. However, MOPITT (Measurements of Pollution in the Troposphere) and SCISAT, two of several atmospheric science research projects sponsored by the Canadian Space Agency, are helping scientists make significant strides in meeting these challenges.

MOPITT is a Canadian-built instrument contributed to an international mission. It measures the movement of carbon monoxide on a global scale-findings that are used in assessing pollution levels in the lower part of the atmosphere, or troposphere.

SCISAT, a fully Canadian mission, was launched in 2003 and carries the Atmospheric Chemistry Experiment (ACE), which focuses mainly on observations related to depletion of the ozone layer in the Earth's upper atmosphere, particularly over Canada and the Arctic. ACE measurements have also been used in studies related to air pollution and climate change.

In August 2003, dozens of fires in British Columbia were filling the skies with smoke. High concentrations of carbon monoxide, up to an altitude of roughly 3 km in the atmosphere, were recorded by MOPITT, a Canadian instrument aboard NASA's Terra satellite. Photo: Government of British Columbia

James Drummond, a University of Toronto physics professor who heads the MOPITT science team, said CO is interesting to scientists for several reasons- it's important for understanding the chemical state of the atmosphere, it identifies sources of biomass burning, and it can be used to trace other pollutants that can't be directly measured.

Carbon monoxide is moved around by air currents in the troposphere and "we can track that," Drummond said. He explained that CO is good for this purpose because it remains in the atmosphere for a period of time; it does not disappear too rapidly to measure, but also does not last so long that it becomes evenly spread around the globe.

This means scientists can treat it as a "proxy for other gases," Drummond said. "It tells us how other chemicals with a similar lifetime are being transported. It's not feasible to track all of them. If you're interested in how much pollution from the Northeastern U.S. makes it into Europe, carbon monoxide is a good tracer."

MOPITT is the first instrument to document the movement of pollutants over long distances across continents and oceans, and it is enabling scientists to create the first global pollution maps.

Drummond said it has detected "significant changes" in carbon monoxide concentrations resulting from forest fires in Siberia and North America, as well as deliberate and natural biomass burning in the tropics. One of the objectives of MOPITT is to track carbon monoxide concentrations over a lengthy period of time to determine trends.

Its original mission of five years has been extended to 10. So far, scientists have been surprised by the annual variability in CO concentrations. "This is the first time we've had this global view," Drummond said. Even just 20 years ago, there was nowhere near the same comprehensive coverage; so determining what's typical "is a more difficult question to answer than we anticipated."

Drummond was also surprised by the "quite staggering" amount of carbon monoxide produced in equatorial regions, where biomass burning is part of the agricultural cycle. The amount of CO produced by this source was not previously known.

Drummond said MOPITT's findings have had a significant impact on atmospheric research. For example, scientists who study other chemicals and pollutants using instruments on the ground or in aircraft use its data. Real-time maps of where carbon monoxide is moving gives them valuable information about where to target their ground-based or airborne instruments.

MOPITT data are also being used to improve computer models of how chemicals move in the lower atmosphere. Such models did not previously exist because "the knowledge wasn't there," Drummond said. "We're starting to see some quite sophisticated models with predictive capabilities."

(Article by Lydia Dotto. Source: Space Science Research in Canada 2004-2005, Beijing, China, July 2006,
The CSA's Report to the 36th COSPAR Meeting)