HR: 12:05h
AN: A42A-08    [Abstracts]
TI: Methane over the North American Continent - INTEX-NA, Summer 2004
AU: * Karen, B
EM: karen.bartlett@unh.edu
AF: Univ. of New Hampshire, CSRC/EOS Morse Hall, Durham, NH 03824 United States
AU: Blake, D
EM: drblake@uci.edu
AF: Univ. of California, Irvine, Dept. of Chemistry, Irvine, CA 92697 United States
AU: Meinardi, S
EM: smeinard@uci.edu
AF: Univ. of California, Irvine, Dept. of Chemistry, Irvine, CA 92697 United States
AU: Blake, N
EM: nblake@uci.edu
AF: Univ. of California, Irvine, Dept. of Chemistry, Irvine, CA 92697 United States
AU: Sachse, G
EM: g.w.sachse@larc.nasa.gov
AF: NASA Langley Res. Center, Chemistry and Dynamics Branch, Hampton, VA 23681 United States
AU: Slate, T
EM: t.a.slate@larc.nasa.gov
AF: Swales Aerospace, c/o NASA Langley Res. Center, Hampton, VA 23681 United States
AB: During July and August of 2004, the INTEX-NA mission was flown over the North American continent as a part of the integrated ICARTT campaign. Its primary focus was to examine the intercontinental transport and transformation of chemically and radiatively important trace gases and aerosols across the region. As a part of the mission, methane (CH4) was sampled using both canisters and a fast response tunable diode laser, the DACOM instrument. Agreement between the two techniques was excellent. Sources of methane are both natural (wetlands, wildfires) and anthropogenically controlled (landfills, ruminants, petroleum production and use, coal mining). Although natural biogenic emissions would be expected to be near seasonal maximums, the majority of North American wetlands are located in Canada and Alaska, and were difficult to isolate during the mission. Overall distributions were well correlated with C2Cl4, a tracer of industrial and urban activity, and reflect the widespread impact of anthropogenic emissions. As expected for a gas with surface continental sources, variability was greatest in the near-surface atmosphere and decreased with increasing altitude and distance from the continent. Summer convective activity over the region resulted in elevated concentrations measured at altitudes above 6 km. Enhanced levels with distinctive trace gas signatures were observed for a variety of sources, including petroleum mining and distribution, coal mining, Canadian wildfires, and aged Asian plumes advected across the Pacific. Several flights during the mission were flown along the U.S. east coast to sample air masses transported off the continent to the Atlantic. In the near-surface over the ocean, clean boundary layer air with mixing ratios comparable to background CMDL levels at this time were encountered. At altitudes above about 4 km, CH4 was enhanced by roughly 20-50 ppb.
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere: composition and chemistry
DE: 0478 Pollution: urban, regional and global (0345, 4251)
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005