nmvoc emissions nmvoc emissions estimated from hcho gome-2 satellite data j-f. muller, j. stavrakou...
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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
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