HR: 1340h
AN: A23C-1465    [Abstracts]
TI: Evidence of a Late-Summer Decrease in NOx/CO Emission Ratios From Boreal Fires
AU: * Lapina, K
EM: klapina@mtu.edu
AF: Civil and Environmental Engineering Department, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AU: Honrath, R
EM: reh@mtu.edu
AF: Civil and Environmental Engineering Department, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AU: Owen, C
EM: rcowen@mtu.edu
AF: Civil and Environmental Engineering Department, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, United States
AU: Val Martin, M
EM: mvalmart@mtu.edu
AF: Atmospheric Chemistry Modeling Group, Division of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford St., Cambridge, MA 02138-2901, United States
AU: Hyer, E J
EM: edward.hyer@nrlmry.navy.mil
AF: Naval Research Lab, Marine Meteorology Division, 7 Grace Hopper Avenue, Monterey, CA 93943, United States
AU: Fialho, P
EM: fialho.paulo@gmail.com
AF: Climate, Meteorology and Global Change Center, Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, PT9701-851, Portugal
AU: Barata, F
EM: barataf@gmail.com
AF: Climate, Meteorology and Global Change Center, Group of Chemistry and Physics of the Atmosphere, University of the Azores, Terra Chã, PT9701-851, Portugal
AB: NO_x emissions from boreal fires are critical to ozone production, but their accurate estimation is currently not possible, due to large uncertainties in emission factors. In this work, we use measurements of CO and NO_y at the free tropospheric Pico Mountain observatory in the central North Atlantic during the active boreal fire seasons of 2004 and 2005 to constrain NO_x/CO emission ratios in North American boreal fires. Observed ΔNO_y/ΔCO enhancement ratios in aged boreal fire plumes indicate that NO_x/CO emission ratios declined significantly as the fire season progressed. This is consistent with our understanding that an increased amount of fuel is consumed via smoldering combustion during late summer, as deeper burning of the drying organic soil layer occurs, leading to an overall increase in CO and a decrease in NO_x fire emission factors. A major growth in overall fuel consumption in the late summer is also expected, due to deeper burning. Emissions of CO and NO_x from the 2004 and 2005 North American boreal fires were estimated using the Boreal Wildland-Fire Emissions Model, taking into account this late-summer increase in depth of burning. The long-range transport of these emissions to the sampling site was modeled using FLEXPART. These simulations were generally consistent with the observations, but the modeled seasonal decline in the ΔNO_y/ΔCO enhancement ratio was less than observed. Comparisons using alternative fire emission injection height scenarios suggest that plumes with the highest CO levels at the Pico Mountain observatory resulted from large fires where emissions were lofted well above the boundary layer.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting