New Satellite-Borne Instrument to Measure Carbon Monoxide Pollution in the Lower Atmosphere

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 builtthe instrument. Data will be assimilated into a comprehensive NCARatmospheric chemistry model, where the first global picture of carbonmonoxide source regions and transport should emerge. NCARís primarysponsor is the National Science Foundation.

Somewhere between two and five billion tons of carbon monoxide enter theatmosphere each year as a by-product of fossil fuel combustion andbiomass burning and through natural emissions from plants. Natural andhuman-related emissions appear to be roughly equal. Aircraft- andground-based instruments have provided a patchwork of measurements inspace 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, SouthAmerica, and Indonesia and wafts over the oceans toward othercontinents," says scientist John Gille, who heads a software group of 20NCAR researchers preparing MOPITT data retrieval and analysis. As thedata analysis becomes more sensitive, says Gille, it should revealcarbon monoxide emissions from heavily polluted cities as well.

Near the earthís surface, carbon monoxide (CO) is a deadly poison whenhighly concentrated. As it rises into the atmosphere, it is convertedinto carbon dioxide, a greenhouse gas, by taking oxygen atoms frommolecules of the hydroxyl radical (OH), an elusive but powerful agentthat cleanses the atmosphere of pollutants. Because of its highreactivity and short lifetime, OH canít be measured from space, butmonitoring CO will open the window to understanding the cleansingprocesses and their implications for pollution levels.

Carbon monoxide is also an excellent tracer for observing globaltransport in the troposphere--a challenge for scientists because of thevagaries of wind and weather. Its lifetime of two months is long enoughfor the gas to be tracked as it rises from the surface and journeysaround the globe, yet short enough to prevent it from mixing evenly inthe atmosphere, which would obscure its sources and paths. MOPITT willmeasure CO concentrations at four levels in the lower atmosphere.

"Because pollutants can travel long distances, thereís no truly pristinearea left on earth, not as we once imagined," says Gille. "Tracking COfrom space is a key to observing our interdependency--including ourability to pollute the globe."

MOPITT will also measure methane, which rises into the air from farnorthern 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 evenlyaround the globe, its sources and tracks are difficult to unravel.Though thereís only a half billion tons of it, the gas absorbs infraredradiation emitted by the earth 60 times more efficiently than carbondioxide does. MOPITT is designed to observe the total vertical column ofmethane.

Aboard NASA's Terra satellite, MOPITT will observe the earth each day at10:30 a.m. and 10:30 p.m. from its sun-synchronous orbit at 705kilometers (437 miles) altitude. Terra is the "flagship" for NASA'sEarth Observing System series of ten satellites designed to providedaily 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 atmosphericand related sciences.