Journal cover Journal topic
Atmospheric Chemistry and Physics An Interactive Open Access Journal of the European Geosciences Union

Journal metrics

  • IF value: 5.298 IF 5.298
  • IF 5-year<br/> value: 5.543 IF 5-year
  • SNIP value: 1.809 SNIP 1.809
  • IPP value: 5.253 IPP 5.253
  • SJR value: 3.830 SJR 3.830
  • h5-index value: 89 h5-index 89
Atmos. Chem. Phys., 11, 5641-5654, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research Article
20 Jun 2011
Free tropospheric peroxyacetyl nitrate (PAN) and ozone at Mount Bachelor: potential causes of variability and timescale for trend detection
E. V. Fischer1, D. A. Jaffe1,2, and E. C. Weatherhead3
1Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
2Science & Technology Program, University of Washington-Bothell, Bothell, WA, USA
3Cooperative Institute for Research in Environmental Science, University of Colorado at Boulder, Boulder, CO, USA

Abstract. We report on the first multi-year springtime measurements of PAN in the free troposphere over the US Pacific Northwest. The measurements were made at the summit of Mount Bachelor (43.979° N, 121.687° W; 2.7 km a.s.l.) by gas chromatography with electron capture detector during spring 2008, 2009 and 2010. This dataset provides an observational estimate of the month-to-month and springtime interannual variability of PAN mixing ratios in this region. Springtime seasonal mean (1 April–20 May) PAN mixing ratios at Mount Bachelor varied from 100 pptv to 152 pptv. The standard deviation of the three seasonal means was 28 pptv, 21 % of the springtime mean. We summarize the interannual variability in three factors expected to drive PAN variability: biomass burning, transport efficiency over the central and eastern Pacific, and transport temperature.

Zhang et al. (2008) used the GEOS-Chem global chemical transport model to show that rising Asian NOx emissions from 2000 to 2006 resulted in a relatively larger positive trend in PAN than O3 over western North America. However the model results only considered monotonic changes in Asian emissions, whereas other factors, such as biomass burning, isoprene emissions or climate change can induce greater variability in the atmospheric concentrations and thus extend the time needed for trend detection. We combined the observed variability in PAN and O3 at Mount Bachelor with a range of possible future trends in these species to determine the observational requirements to detect such trends. Though the relative increase in PAN is expected to be larger than that of O3, PAN is more variable. If PAN mixing ratios are currently increasing at a rate of 4 % per year due to rising Asian emissions, we would detect a trend with 13 years of measurements at a site like Mount Bachelor. If the corresponding trend in O3 is 1 % per year, the trends in O3 and PAN would be detected on approximately the same timescale.

Citation: Fischer, E. V., Jaffe, D. A., and Weatherhead, E. C.: Free tropospheric peroxyacetyl nitrate (PAN) and ozone at Mount Bachelor: potential causes of variability and timescale for trend detection, Atmos. Chem. Phys., 11, 5641-5654, doi:10.5194/acp-11-5641-2011, 2011.
Search ACP
Final Revised Paper
Discussion Paper