HR: 08:15h
AN: A41D-02    [Abstracts]
TI: Large Enhancements of Nitrogen Oxides Over the Central North Atlantic Lower Free Troposphere Resulting From Boreal Wildfires: Observations at the PICO-NARE Station During Summer 2004
AU: * Val Martin, M
EM: mvalmart@mtu.edu
AF: Civil and Environmental Eng. Dept., Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931 United States
AU: Honrath, R E
EM: reh@mtu.edu
AF: Civil and Environmental Eng. Dept., Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931 United States
AU: Owen, R C
EM: rcowen@mtu.edu
AF: Civil and Environmental Eng. Dept., Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931 United States
AU: Kleissl, J
EM: kleissl@mtu.edu
AF: Civil and Environmental Eng. Dept., Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931 United States
AU: Fialho, P
EM: fialho.paulo@gmail.com
AF: Grupo de Quimica e Fisica da Atmosfera, Universidade dos Acores, Terra-Cha, Terceira, AZ 9701-851 Portugal
AU: Pfister, G
EM: pfister@ucar.edu
AF: Atmospheric Chemistry Division/National Center for Atmospheric Research, P.O.Box 3000 , Boulder, CO 80307-3000 United States
AU: Lapina, K
EM: klapina@mtu.edu
AF: Civil and Environmental Eng. Dept., Michigan Technological University, 1400 Townsend Dr., Houghton, MI 49931 United States
AB: Extensive wildfires burned in Alaska and western Canada during the summer of 2004. Boreal wildfires are a large source of trace gases and aerosols in the atmosphere. However, little is known about the impact of their emissions on the nitrogen oxides and O₃ levels over the Northern Hemisphere. During the summer of 2004, measurements of NO_x and NO_y were made at the PICO-NARE station (Azores Islands, Portugal, 2225 m asl), a location 5--15 days downwind from the fires. Measurements in 10 fire plumes between July and September were analyzed in combination with CO and aerosol black carbon observations, backward trajectories, satellite images, and MOZART simulations, in order to study the effect of boreal fire emissions on nitrogen oxides levels over the central North Atlantic lower free troposphere, and their further potential for O₃ formation over this region. During the fire-impacted periods, NO_x, NO_y, and CO levels were extremely high for such a remote region, with enhancements up to 110 pptv, 1000 pptv, 150 ppbv above background, respectively. NO_y was significantly correlated to CO, with an average enhancement ratio of approximately 6 pptv/ppbv. The magnitude of the NO_y/CO enhancement ratio is a significant fraction (~20%) of the estimated NO_x/CO emission ratio from boreal forest fires and is only moderately smaller than previous measurements closer to fires, indicating limited NO_y removal during transport to the site. In addition to NO_y, NO_x was typically correlated to CO, with an average enhancement ratio of approximately 1 pptv/ppbv. Since the major component of NO_y in boreal fires plumes is believed to be PAN, this suggests that decomposition of PAN to NO_x is a significant source of NO_x in the fire plumes arriving to this region. These observations indicate that nitrogen oxides emissions from wildfires can be efficiently transported to the lower free troposphere over the central North Atlantic region. Furthermore, high levels of NO_x and NO_y in these well-aged boreal fire plumes indicate continuing O₃ formation. Since these measurements were made very far downwind from the fires, this implies large-scale impacts of boreal fires on the tropospheric O₃ budget.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0365 Troposphere: composition and chemistry
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005