Dec. 21, 1999 BOULDER--A new space-based instrument capable of long-term global observations of carbon monoxide and methane in the lower atmosphere was launched December 19th from Vandenberg Air Force Base. Called MOPITT (Measurements of Pollution in the Troposphere), the instrument could provide new insight into the chemical complexity and dynamic variability of the lower atmosphere, where weather evolves and humans routinely disturb the environment.
Scientists at the National Center for Atmospheric Research (NCAR) developed the software for MOPITT, a Canadian Space Agency experiment, with funding from the National Aeronautics and Space Administration (NASA). CSA researchers developed the measurement technique and built the instrument. Data will be assimilated into a comprehensive NCAR atmospheric chemistry model, where the first global picture of carbon monoxide source regions and transport should emerge. NCARís primary sponsor is the National Science Foundation.
Somewhere between two and five billion tons of carbon monoxide enter the atmosphere each year as a by-product of fossil fuel combustion and biomass burning and through natural emissions from plants. Natural and human-related emissions appear to be roughly equal. Aircraft- and ground-based instruments have provided a patchwork of measurements in space and time, but the complete picture has eluded scientists thus far.
"MOPITT will give us a chance to watch carbon monoxide plume by plume, day by day, as it rises above major source fires in Africa, South America, and Indonesia and wafts over the oceans toward other continents," says scientist John Gille, who heads a software group of 20 NCAR researchers preparing MOPITT data retrieval and analysis. As the data analysis becomes more sensitive, says Gille, it should reveal carbon monoxide emissions from heavily polluted cities as well.
Near the earthís surface, carbon monoxide (CO) is a deadly poison when highly concentrated. As it rises into the atmosphere, it is converted into carbon dioxide, a greenhouse gas, by taking oxygen atoms from molecules of the hydroxyl radical (OH), an elusive but powerful agent that cleanses the atmosphere of pollutants. Because of its high reactivity and short lifetime, OH canít be measured from space, but monitoring CO will open the window to understanding the cleansing processes and their implications for pollution levels.
Carbon monoxide is also an excellent tracer for observing global transport in the troposphere--a challenge for scientists because of the vagaries of wind and weather. Its lifetime of two months is long enough for the gas to be tracked as it rises from the surface and journeys around the globe, yet short enough to prevent it from mixing evenly in the atmosphere, which would obscure its sources and paths. MOPITT will measure CO concentrations at four levels in the lower atmosphere.
"Because pollutants can travel long distances, thereís no truly pristine area left on earth, not as we once imagined," says Gille. "Tracking CO from space is a key to observing our interdependency--including our ability to pollute the globe."
MOPITT will also measure methane, which rises into the air from far northern wetlands and subtropical rice paddies, as well as from cows, sheep, termites, natural gas leaks, and other sources. A greenhouse gas, methane has a lifetime of ten years. With plenty of time to mix evenly around the globe, its sources and tracks are difficult to unravel. Though thereís only a half billion tons of it, the gas absorbs infrared radiation emitted by the earth 60 times more efficiently than carbon dioxide does. MOPITT is designed to observe the total vertical column of methane.
Aboard NASA's Terra satellite, MOPITT will observe the earth each day at 10:30 a.m. and 10:30 p.m. from its sun-synchronous orbit at 705 kilometers (437 miles) altitude. Terra is the "flagship" for NASA's Earth Observing System series of ten satellites designed to provide daily information on the health of the planet.
NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences.
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