HR: 17:45h
AN: A44C-07    [Abstracts]
TI: Seasonal Variation of Nitrogen Oxides in the Central North Atlantic Lower Free Troposphere: Influence of Boreal Wildfires and North American Urban Pollution
AU: * Val Martin, M
EM: mvalmart@mtu.edu
AF: Michigan Tech, Dept. of Civil and Environmental Engineering, 1400 Townsend Dr, Houghton, MI 49931, United States
AU: Honrath, R
EM: reh@mtu.edu
AF: Michigan Tech, Dept. of Civil and Environmental Engineering, 1400 Townsend Dr, Houghton, MI 49931, United States
AU: Owen, C
EM: rcowen@mtu.edu
AF: Michigan Tech, Dept. of Civil and Environmental Engineering, 1400 Townsend Dr, Houghton, MI 49931, United States
AU: Lapina, K
EM: klapina@mtu.edu
AF: Michigan Tech, Dept. of Civil and Environmental Engineering, 1400 Townsend Dr, Houghton, MI 49931, United States
AU: Li, Q
EM: qinbin.li@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183- 501, Pasadena, CA 91109, United States
AU: Shim, C
EM: changsub.shim@jpl.nasa.gov
AF: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., M/S 183- 501, Pasadena, CA 91109, United States
AB: Measurements of NO, NO₂ and NO_y (total reactive nitrogen oxides) made at the Pico Mountain station (38.78° N 28.67° W, 2.3~km asl) from July 2002 to August 2005 are analyzed to characterize the seasonal variation and the speciation of nitrogen oxides in the background lower free troposphere (FT) over the central North Atlantic region. These observations reveal a well-defined seasonal cycle of nitrogen oxides (NO_x = NO+NO₂ and NO_y), with higher mixing ratios during the summertime. Observed NO_x and NO_y levels are consistent with long-range transport of emissions, but with significant removal en-route to the measurement site. Larger summertime nitrogen oxides levels are attributed to impacts of boreal wildfire emissions and more efficient export of NO_y from eastern North America during this season. Reactive nitrogen over the central North Atlantic lower FT largely exists in the form of PAN and HNO₃ (~80--90% of NO_y) year-round. A shift in the composition of NO_y from dominance of PAN to dominance of HNO₃ occurred from winter--spring to summer--fall, as a result of changes in temperature and photochemistry over the region. A further comparison of the nitrogen oxides measurements with results from the global chemical transport model GEOS-Chem identifies differences between the observations and the model, with simulated nitrogen oxides significantly larger than the observations.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting