NMVOC emissions NMVOC emissions estimated from HCHO GOME-2 satellite data J-F. Muller, J. Stavrakou I. De Smedt, M. Van Roozendael Belgian Institute for Space Aeronomy Brussels, Belgium GEIA/ACCENT Workshop, Oslo, Oct. 2009

H : model operator acting on the control variables y : observations f B : 1st guess values of the control variables E : observation error covariance matrix B : error covariance matrix on the control variables f : control variables vector Cost function : measure of the discrepancy between the model and the observations J(f)=½Σ i (H i (f)-y i ) T E -1 (H i (f)-y i ) + ½ (f-f B ) T B -1 (f-f B ) Inverse modeling: constrain/improve emission inventories based on atmospheric chemical observations and an atmospheric model - Choice of control parameters - Emission categories - Spatial resolution of the inversion - Temporal resolution - Results depend on assumed error covariance matrices for observations and control variables

Potential of spaceborne HCHO columns to yield quantitative information on NMVOC emissions (Palmer et al., 2003, 2006, Fu et al., 2007, Dufour et al., 2009, Stavrakou et al., 2009) NMVOCs : short-lived compounds, ozone and SOA precursors large uncertainties in emissions/speciation 85% 12% 3% Biogenic Anthropogenic Biomass burning Globally ~1200 Tg/year CH 4 oxidation, 60% Biogenic NMVOCs 30% Anth. 7% Fires, 3% Global total HCHO ca Tg/yr Lifetime = 5 h GLOBAL HCHO BUDGET NMVOCs EMISSIONS

10 15 molec. cm -2 IMAGESv2 HCHO columns SCIAMACHY HCHO (BIRA-IASB)‏ Inverse modeling: derive updated NMVOC emissions by adjusting the emissions used in the CTM so as to minimize the model/data biases Adjoint technique : powerful tool for non-linear problems with a large number of unknowns  inversions at the model resolution, distinguish between emission categories

Updated/prior pyrogenic emissions Updated/prior biogenic emissions large decrease over the Northern african savanna & over Indonesia, up to x2 increase over S. Africa strong increase over South Africa 30% reduction over N. America (consistent with independent evaluation of isoprene emissions based on aircraft data) 30% decrease over Indonesia Inversion results using SCIAMACHY HCHO data and IMAGES at 5°x5° resolution (Stavrakou et al., 2009) HCHO data clearly provide useful constraints for biogenic NMVOC (isoprene) emissions and biomass burning, BUT

anthropogenic sources are significant over populated/industrialized areas, but their contribution is small (7%) at the global scale over the US: big cities/anthropogenic signal not clearly identified by SCIAMACHY/OMI (Millet et al., 2008) in constrast, significant enhancement observed over Chinese cities using 6- year averaged GOME data (Fu et al., 2007) Anthropogenic NMVOC signal in the HCHO columns? GOME-2/Metop : successor of GOME and SCIAMACHY, launched in October 2006 global coverage in 1.5 day  higher signal-to-noise ratio

2008 GOME-2 HCHO January July IMAGESv2 HCHO (now at 2°x2.5°) molec.cm -2

AnthropogenicBiogenic (isoprene) A priori emissions Correction factors Far East : +50%, Europe: -30%, N.America: -40% patterns roughly similar to inversion results using SCIAMACHY HCHO

Updated/a priori anthropogenic emissions July % increase over China, +70% over India China: 27 Tg/yr in 2008, 17.2 Tg/yr in REAS (Ohara et al., 2007) for 2003 Fu et al inversion using GEOS-Chem and GOME: anthropogenic +25%, biogenic x4, b.burning x9

Modeled HCHO column using a priori emissions Updated HCHO column GOME-2 HCHO column over the Far East molec.cm -2 July 2008

Summary For biogenic emissions and biomass burning, consistency of the updated emissions with inversions based on SCIAMACHY HCHO Global isoprene emission = 400 Tg/year However, strong evidence from field campaigns, theoretical and laboratory studies that the isoprene oxidation mechanism should be revisited (Lelieveld et al. 2008, Peeters et al. 2009, Paulot et al. 2009) Reduction of anthropogenic VOC emission over Europe, US and Middle East Factor of 2 increase for anthropogenic Chinese emissions, +70% in India However, optimization fails to reproduce high HCHO levels over these regions More work needed to refine the chemical oxidation scheme to include more explicit anthropogenic precursors of HCHO