NMVOC emissions NMVOC emissions

estimated from HCHOestimated from HCHO

GOME-2 satellite data 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, 26-29 Oct. 2009

H : model operator acting on the control

variables

y :

observations

fB : 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)=½Σi (Hi(f)-yi)T E-1(Hi(f)-yi) + ½ (f-fB)TB-1(f-fB)

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

CH4 oxidation, 60%

Biogenic NMVOCs

30% Anth. 7%

Fires, 3%

Global total HCHO ca. 1600 Tg/yr Lifetime = 5 h

GLOBAL HCHO BUDGET

NMVOCs EMISSIONS

1015 molec. cm-2

IMAGESv2 HCHO columnsSCIAMACHY 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°)

1015 molec.cm-2

Anthropogenic Biogenic (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 2008

+95% 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. 2007 inversion using GEOS-Chem and 1996-2001 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

1015 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

jfm@aeronomie.be

http://tropo.aeronomie.be