Atmos. Chem. Phys. Discuss., 8, 19273-19312, 2008
© Author(s) 2008. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
SCIAMACHY formaldehyde observations: constraint for isoprene emissions over Europe?
G. Dufour1, F. Wittrock2, M. Camredon1,*, M. Beekmann1, A. Richter2, and J. Burrows2
1Laboratoire Inter-universitaire des Systèmes Atmosphériques (LISA), UMR7583, Universités Paris 12 et Paris 7, CNRS, Créteil, France
2Institute of Environmental Physics and Remote Sensing, University of Bremen, Bremen, Germany
*now at: School of Geography, Earth and Environment Sciences, University of Birmingham, Edgbaston, Birmingham, UK

Abstract. Formaldehyde (HCHO) is an important intermediate compound in the degradation of volatile organic compounds (VOCs) in the troposphere. Sources of HCHO are largely dominated by its secondary production from VOC oxidation, methane and isoprene being the main precursors in unpolluted areas. As a result of the moderate lifetime of HCHO, its spatial distribution is determined by reactive hydrocarbon emissions. We focus here on Europe, never studied before, and investigate the influence of the different emissions on HCHO tropospheric columns with the CHIMERE chemical transport model in order to interpret the comparisons between SCIAMACHY and simulated HCHO columns. Observed columns present a bias less than 20% on average. The differences are discussed according to the errors on the model and the observations and the remaining discrepancies are attributed to a misrepresentation of biogenic emissions. This study requires the characterisation of: (1) the model errors and performances concerning formaldehyde. The errors on the HCHO columns, mainly related to chemistry and mixed emission types, are evaluated to 2×1015 molecule/cm2 and the model performances evaluated using surface measurements are satisfactory (~13%); (2) the observation errors that define the needs in spatial and temporal averaging for meaningful comparisons. Perspectives of using SCIAMACHY observations as constraint for biogenic isoprene emissions with an adapted averaging are approached: this new constraint should help to reduce their uncertainties more than 50% in region of intense emissions.

Citation: Dufour, G., Wittrock, F., Camredon, M., Beekmann, M., Richter, A., and Burrows, J.: SCIAMACHY formaldehyde observations: constraint for isoprene emissions over Europe?, Atmos. Chem. Phys. Discuss., 8, 19273-19312, doi:10.5194/acpd-8-19273-2008, 2008.
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