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Combined formaldehyde and glyoxal observations from GOME-2 backscattered light measurements.

Christophe Lerot(1), Isabelle De Smedt(1), Jean-François Müller(1), Trissevgeni Stavrakou(1) and Michel Van Roozendael(1)

(1) Belgian Institute for Space Aeronomy, Avenue circulaire 3, 1180 Brussels, Belgium

Abstract

Glyoxal (CHOCHO) and formaldehyde (HCHO) are short-lived intermediate products in the oxidation of non-methane volatile organic compounds (NMVOCs) emitted by vegetation, fires and anthropogenic activities. They are also directly emitted during fossil fuel and biofuel combustion and biomass burning. Both compounds absorb in the UV-visible spectral region which can be used for total column retrieval using the Differential Optical Absorption Spectroscopy (DOAS) technique. However, such measurements remain challenging mainly due to the overall faintness of the CHOCHO and HCHO signals, but also due to uncertainties in the calculation of air mass factors (AMFs).

Launched in October 2006 on board of METOP-A platform, the GOME-2 instrument measures the sunlight backscattered by the Earth’s atmosphere between 240 nm and 790 nm, with a ground resolution of 80 km x 40 km. Compared to its predecessors GOME/ERS-2 and SCIAMACHY/ENVISAT, GOME-2 is characterized by a larger scan-width of 1920 km allowing for daily quasi-global coverage and therefore for a much better observation of the NMVOC emissions.

In this work, we present results of glyoxal and formaldehyde vertical columns from two years of GOME-2 observations (2007 and 2008). We compare the global observations of these two compounds as well as their seasonalities. Specific attention will be focused on the Southeastern Asia where the anthropogenic emissions in the rapidly growing Megacities are important. The synergistic use of glyoxal and formaldehyde observations offers the potential to provide better constraints to anthropogenic NMVOC emissions using inverse modeling techniques as illustrated in the companion abstract of Müller et al.

 

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