Nitrogen oxides and PAN in plumes from boreal fires during ARCTAS-B and their impact on ozone: an integrated analysis of aircraft and satellite observations
1School of Engineering and Applied Science, Harvard University, Cambridge, Massachusetts, USA
2Now at Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA
3Atmospheric Chemistry Division, National Center for Atmospheric Research, Boulder, Colorado, USA
4Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, USA
5School of Physical Sciences, University of California, Irvine, California, USA
6Chemistry Department, University of California, Berkeley, California, USA
7NASA Langley Research Center, Hampton, Virginia, USA
8Department of Meteorology, Florida State University, Tallahassee, Florida, USA
9School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA.
10Department of Chemistry and Cooperative Institute for Research in the Environmental Sciences, University of Colorado, Boulder, Colorado, USA
11California Institute of Technology, Pasadena, California, USA
12Institut für Ionenphysik & Angewandte Physik, University of Innsbruck, Innsbruck, Austria
Abstract. We determine enhancement ratios for NOx, PAN, and other NOy species from boreal biomass burning using aircraft data obtained during the ARCTAS-B campaign and examine the impact of these emissions on tropospheric ozone in the Arctic. We find an initial emission factor for NOx of 1.06 g NO per kg dry matter (DM) burned, much lower than previous observations of boreal plumes, and also one third the value recommended for extratropical fires. Our analysis provides the first observational confirmation of rapid PAN formation in a boreal smoke plume, with 40% of the initial NOx emissions being converted to PAN in the first few hours after emission. We find little clear evidence for ozone formation in the boreal smoke plumes during ARCTAS-B in either aircraft or satellite observations, or in model simulations. Only a third of the smoke plumes observed by the NASA DC8 showed a correlation between ozone and CO, and ozone was depleted in the plumes as often as it was enhanced. Special observations from the Tropospheric Emission Spectrometer (TES) also show little evidence for enhanced ozone in boreal smoke plumes between 15 June and 15 July 2008. Of the 22 plumes observed by TES, only 4 showed ozone increasing within the smoke plumes, and even in those cases it was unclear that the increase was caused by fire emissions. Using the GEOS-Chem atmospheric chemistry model, we show that boreal fires during ARCTAS-B had little impact on the median ozone profile measured over Canada, and had little impact on ozone within the smoke plumes observed by TES.