Observations of peroxyacetyl nitrate (PAN) in the upper troposphere by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS) 1Department of Chemistry, University of York, Heslington, York, UK
06 Jun 2013
2National Centre for Earth Observation (NCEO), Department of Physics & Astronomy, University of Leicester, Leicester, UK
3Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada
4National Center for Atmospheric Research (NCAR), Boulder, Colorado, USA
5Department of Chemistry & Biochemistry, Old Dominion University, Norfolk, Virginia, USA
Received: 20 Dec 2012 – Published in Atmos. Chem. Phys. Discuss.: 15 Jan 2013Abstract. Peroxyacetyl nitrate (CH3CO·O2NO2, abbreviated as PAN)
is a trace molecular species present in the troposphere and lower
stratosphere due primarily to pollution from fuel combustion and the
pyrogenic outflows from biomass burning. In the lower troposphere, PAN has a
relatively short lifetime and is principally destroyed within a few hours
through thermolysis, but it can act as a reservoir and carrier of
NOx in the colder temperatures of the upper troposphere, where UV
photolysis becomes the dominant loss mechanism. Pyroconvective updrafts from
large biomass burning events can inject PAN into the upper troposphere and
lower stratosphere (UTLS), providing a means for the long-range transport of
NOx. Given the extended lifetimes at these higher altitudes, PAN is
readily detectable via satellite remote sensing.
Revised: 25 Apr 2013 – Accepted: 12 May 2013 – Published: 06 Jun 2013
A new PAN data product is now available for the Atmospheric Chemistry
Experiment Fourier Transform Spectrometer (ACE-FTS) version 3.0
data set. We report observations of PAN in boreal biomass burning plumes
recorded during the BORTAS
(quantifying the impact of BOReal forest fires on
Tropospheric oxidants over the Atlantic using Aircraft and Satellites) campaign (12 July to 3 August 2011). The retrieval
method employed by incorporating laboratory-recorded absorption
cross sections into version 3.0 of the ACE-FTS forward model
and retrieval software is described in full detail. The estimated detection
limit for ACE-FTS PAN is 5 pptv, and the total systematic error contribution
to the ACE-FTS PAN retrieval is ~ 16%.
The retrieved volume mixing ratio (VMR) profiles are compared to coincident
measurements made by the Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS) instrument on the European Space Agency (ESA) Environmental
Satellite (ENVISAT). The MIPAS measurements demonstrated good agreement with
the ACE-FTS VMR profiles for PAN, where the measured VMR values
are well within the associated measurement errors for both instruments and
comparative measurements differ no more than 70 pptv.
The ACE-FTS PAN data set is used to obtain zonal mean
distributions of seasonal averages from ~ 5–20 km. A strong
seasonality is clearly observed for PAN concentrations in the global UTLS.
Since the principal source of PAN in the UTLS is due to lofted biomass
burning emissions from the pyroconvective updrafts created by large fires,
the observed seasonality in enhanced PAN coincides with fire activity in
different geographical regions throughout the year.
Citation: Tereszchuk, K. A., Moore, D. P., Harrison, J. J., Boone, C. D., Park, M., Remedios, J. J., Randel, W. J., and Bernath, P. F.: Observations of peroxyacetyl nitrate (PAN) in the upper troposphere by the Atmospheric Chemistry Experiment-Fourier Transform Spectrometer (ACE-FTS), Atmos. Chem. Phys., 13, 5601-5613, doi:10.5194/acp-13-5601-2013, 2013.