SCIAMACHY formaldehyde observations: constraint for isoprene emission estimates over Europe?

Abstract

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 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 SCIA-MACHY and simulated HCHO columns. Europe was never specifically studied before for these purposes using satellite observations. The bias between measurements and model is less than 20% on average. The differences are discussed according to the errors on the model and the observations and 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 2×10 15 molecule/cm 2 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. Using SCIAMACHY observations as constraint for biogenic isoprene emissions in an inverse modelling scheme reduces their uncertainties by about a factor of two in region of intense emissions. The retrieved correction factors for the isoprene emissions range from a factor of 0.15 (North Africa) to a factor of 2 (Poland, the United Kingdom) depending on the regions.

Improved retrieval of global tropospheric formaldehyde columns from GOME-2/MetOp-A addressing noise reduction and instrumental degradation issues

“…The precision of the current GOME and SCIAMACHY H 2 CO datasets does not allow for a better time/space resolution than monthly averaged columns over rather large regions in order to sufficiently reduce the noise in the observations (see e.g. Dufour et al, 2009). The better sampling rate of GOME-2 allows for a significant reduction of the noise in the averaged columns.…”

Isoprene emissions in Africa inferred from OMI observations of formaldehyde columns

“…Contributions from other biogenic or anthropogenic NMVOCs are generally much weaker because emissions are lower and/or HCHO production is slower , although care is needed to screen biomass burning and large anthropogenic influences (Fu et al, 2007;Barkley et al, 2008). Inference of isoprene emissions from HCHO column measurements by the GOME (1995 launch), SCIA-MACHY (2002), andOMI (2004) satellite instruments has been reported in a number of studies for North America Palmer et al, 2003Palmer et al, , 2006Millet et al, 2008), Asia (Fu et al, 2007), Europe (Dufour et al, 2009;Curci et al, 2010), South America (Barkley et al, 2008), and globally (Shim et al, 2005;Stavrakou et al, 2009a).…”

Ground-based FTIR and MAX-DOAS observations of formaldehyde at Réunion Island and comparisons with satellite and model data

“…Formaldehyde total columns have been observed from space by GOME and SCIAMACHY (Abbot et al, 2003;De Smedt et al, 2008;Dufour et al, 2009). Comparisons between SCIAMACHY and ground-based MAX-DOAS (Multi-AXis Differential Optical Absorption Spectroscopy) formaldehyde total columns have been presented in Wittrock et al (2006).…”