Atmos. Chem. Phys. Discuss., 10, 14771-14814, 2010
www.atmos-chem-phys-discuss.net/10/14771/2010/
doi:10.5194/acpd-10-14771-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Formic acid above the Jungfraujoch during 1985–2007: observed variability, seasonality, but no long-term background evolution
R. Zander1, P. Duchatelet1, E. Mahieu1, P. Demoulin1, G. Roland1, C. Servais1, J. Vander Auwera2, A. Perrin3, C. P. Rinsland4, and P. Crutzen5
1Institute of Astrophysics and Geophysics, University of Liège, 4000, Liège, Belgium
2Service de Chimie Quantique et Photophysique, Université Libre de Bruxelles, 1050, Brussels, Belgium
3Laboratoire Interuniversitaire de Systèmes Atmosphériques, CNRS, Université de Paris 12 et 7, 94010 Créteil cedex, France
4NASA Langley Research Center, Hampton, VA 23681-2199, USA
5Max Planck Institute for Chemistry, Airchemistry Division, Mainz, Germany

Abstract. This paper reports on daytime total vertical column abundances of formic acid (HCOOH) above the Northern mid-latitude, high altitude Jungfraujoch station (Switzerland; 46.5° N, 8.0° E, 3580 m altitude). The columns were derived from the analysis of infrared solar observations regularly performed with high spectral resolution Fourier transform spectrometers during over 1537 days between September 1985 and September 2007. The investigation was based on the spectrometric fitting of five spectral intervals, one encompassing the HCOOH ν6 band Q branch at 1105 cm−1, and four additional ones allowing to optimally account for critical temperature-sensitive or timely changing interferences by other atmospheric gases, in particular HDO, CCl2F2 and CHClF2. The main results derived from the 22 yr long database indicate that the free tropospheric burden of HCOOH above the Jungfraujoch undergoes important short-term daytime variability, diurnal and seasonal modulations, inter-annual anomalies, but no statistically significant long-term background change at the 1-sigma level.

A major progress in the remote determination of the atmospheric HCOOH columns reported here has resulted from the adoption of new, improved absolute spectral line intensities for the infrared ν6 band of trans-formic acid, resulting in retrieved free tropospheric loadings being about a factor two smaller than if derived with previous spectroscopic parameters. Implications of this significant change with regard to earlier remote measurements of atmospheric formic acid and comparison with relevant Northern mid-latitude in situ findings will be assessed critically. Sparse HCOOH model predictions will also be evoked.


Citation: Zander, R., Duchatelet, P., Mahieu, E., Demoulin, P., Roland, G., Servais, C., Vander Auwera, J., Perrin, A., Rinsland, C. P., and Crutzen, P.: Formic acid above the Jungfraujoch during 1985–2007: observed variability, seasonality, but no long-term background evolution, Atmos. Chem. Phys. Discuss., 10, 14771-14814, doi:10.5194/acpd-10-14771-2010, 2010.
 
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