The continental source of glyoxal estimated by the synergistic use of spaceborne measurements and inverse modelling 1Belgian Institute for Space Aeronomy, Avenue Circulaire 3, 1180, Brussels, Belgium
2ECPL, Department of Chemistry, University of Crete, Heraklion, Greece
3Institute of Environmental Physics, University of Bremen, Bremen, Germany
4Centre for Ecology and Hydrology, Maclean Building, Benson Lane, Crowmarsh Gifford, Wallingford, Oxfordshire, OX10 8BB, UK
Received: 15 April 2009 – Published in Atmos. Chem. Phys. Discuss.: 19 June 2009 Abstract. Tropospheric glyoxal and formaldehyde columns retrieved from the SCIAMACHY satellite
instrument in 2005 are used with the IMAGESv2 global chemistry-transport model and
its adjoint in a two-compound inversion scheme designed to estimate the continental
source of glyoxal. The formaldehyde observations provide an important constraint
on the production of glyoxal from isoprene in the model, since the degradation of
isoprene constitutes an important source of both glyoxal and formaldehyde.
Current modelling studies underestimate largely the observed glyoxal satellite
columns, pointing to the existence of an additional land glyoxal source of biogenic
origin. We include an extra glyoxal source in the model and we explore its possible
distribution and magnitude through two inversion experiments. In the first case, the
additional source is represented as a direct glyoxal emission, and in the second, as
a secondary formation through the oxidation of an unspecified glyoxal precursor.
Besides this extra source, the inversion scheme optimizes the primary glyoxal and
formaldehyde emissions, as well as their secondary production from other identified
non-methane volatile organic precursors of anthropogenic, pyrogenic and biogenic origin.
Revised: 21 September 2009 – Accepted: 11 October 2009 – Published: 05 November 2009
In the first inversion experiment, the additional direct source, estimated at 36 Tg/yr,
represents 38% of the global continental source, whereas the contribution of
isoprene is equally important (30%), the remainder being accounted for by
anthropogenic (20%) and pyrogenic fluxes. The inversion succeeds in reducing
the underestimation of the glyoxal columns by the model, but it leads to a severe
overestimation of glyoxal surface concentrations in comparison with in situ
measurements. In the second scenario, the inferred total global continental glyoxal
source is estimated at 108 Tg/yr, almost two times higher than the global a priori
source. The extra secondary source is the largest contribution to the global glyoxal
budget (50%), followed by the production from isoprene (26%) and from anthropogenic
NMVOC precursors (14%). A better performance is achieved in this case, as the updated
emissions allow for a satisfactory agreement of the model with both satellite and in
situ glyoxal observations.
Citation: Stavrakou, T., Müller, J.-F., De Smedt, I., Van Roozendael, M., Kanakidou, M., Vrekoussis, M., Wittrock, F., Richter, A., and Burrows, J. P.: The continental source of glyoxal estimated by the synergistic use of spaceborne measurements and inverse modelling, Atmos. Chem. Phys., 9, 8431-8446, doi:10.5194/acp-9-8431-2009, 2009.