MAPPING OF VOLATILE ORGANIC COMPOUND VOC EMISSIONS USING SATELLITE OBSERVATIONS OF FORMALDEHYDE COLU

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MAPPING OF VOLATILE ORGANIC COMPOUND (VOC)
EMISSIONS USING SATELLITE OBSERVATIONSOF
FORMALDEHYDE COLUMNSDaniel J. Jacob
with Paui I. Palmer, Tzung-May Fu, Dylan B.
Millet, Dorian S. Abbot
and Kelly V. Chance, Thomas Kurosu (Harvard
SAO/CFA)
supported by NASA Atmospheric Chemistry Modeling
and Analysis Program
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SATELLITE OBSERVATIONS OF TROPOSPHERIC
COMPOSITIONa rapidly growing resource!
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IMPORTANCE OF NON-METHANE VOC EMISSIONS FOR
ATMOSPHERIC CHEMISTRY

• Precursors of tropospheric ozone
• Precursors of organic aerosols
• Sinks of OH

Alkanes, alkenes, aromatics
Isoprene, terpenes, oxygenates
Alkenes, aromatics, oxygenates
200 Tg C yr-1
600 Tg C yr-1
50 Tg C yr-1
Industry
Vegetation
Biomass burning
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SPACE-BASED MEASUREMENTS OF HCHO COLUMNSAS
CONSTRAINTS ON VOC EMISSIONS
solar backscatter
340 nm
hn (l lt 345 nm), OH
Oxidation (OH, O3, NO3)
VOC
HCHO
lifetime of hours
many steps
Emissions
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SPACE-BASED MEASUREMENTS OF ATMOSPHERIC COLUMNS
BY SOLAR BACKSCATTER
Examples TOMS, GOME, SCIAMACHY, MODIS, MISR,
OMI, OCO Applications to retrievals of O3, NO2,
HCHO, BrO, CO, CO2, aerosols
absorption
Backscattered intensity IB
l1
l2
wavelength
Slant optical depth
Scattering by Earth surface and by atmosphere
Slant column
Vertical column
The air mass factor (AMF) depends on viewing
geometry and radiative transfer
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THE GOME INSTRUMENT

• Instrument in polar sun-synchronous orbit, 1030
  a.m. observation time
• 320x40 km2 field of view, three cross-track
  scenes
• Complete global coverage in 3 days
• Operational since 1995
• HCHO column is determined from backscattered
  solar radiance in 340 nm absorption band
• Concurrent retrievals of cloud fractions, tops,
  optical depths

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FITTING OF HCHO SLANT COLUMNS FROM GOME SPECTRA
ts 1.0 0.3 x1016 cm-2
Fitting uncertainty of 4x1015 molecules
cm-3 corresponds to 1 ppbv HCHO in lowest 2 km
ts 3.0 0.4 x1016 cm-2
ts 8.4 0.7 x1016 cm-2
Chance et al. 2000
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HCHO SLANT COLUMNS MEASURED BY GOME (JULY 1996)
2.5x1016 molecules cm-2
2
1.5
1
detection limit
0.5
South Atlantic Anomaly (disregard)
0
-0.5
High HCHO regions reflect VOC emissions from
fires, biosphere, human activity
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AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN WS
TO VERTICAL COLUMN W
Geometric AMF (AMFG) for non-scattering
atmosphere
EARTH SURFACE
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IN SCATTERING ATMOSPHERE, AMF DEPENDS ON VERTICAL
DISTRIBUTION OF ABSORBER
340 nm
HCHO
EARTH SURFACE
Use GEOS-Chem chemical transport model to specify
shape of vertical profile for given scene
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AMF FOR A SCATTERING ATMOSPHERE
AMFG 2.08 actual AMF 0.71
Palmer et al. 2001
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QUANTIFYING AMF ERRORS USING AIRCRAFT PROFILES
ICARTT mission over North America (summer 2004)
0-10 km spirals and profiles during ICARTT In
situ HCHO, clouds, aerosol extinction
Mean HCHO profiles in ICARTT
Observed (Fried) Observed (Heikes) GEOS-Chem model
(n 89)
Dylan B. Millet, Harvard
Clouds are the principal source of error
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FORMALDEHYDE COLUMNS FROM GOME July 1996 means
compare to GEOS-Chem including GEIA biogenic
VOC emissions and U.S. EPA anthropogenic VOC
emissions GEOS-Chem vs. GOME R 0.83, bias
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Palmer et al. 2003
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SEASONALITY OF GOME HCHO COLUMNS
(9/96-8/97)largely reflects seasonality of
isoprene emissions
GOME GEOS-Chem (GEIA)
GOME GEOS-Chem (GEIA)
JUL
MAR
AUG
APR
SEP
MAY
JUN
OCT
Abbot et al. 2003
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INTERANNUAL VARIABILITY OF GOME HCHO COLUMNS
Augusts 1995-2001 correlation with temperature
anomaly explains some but not all of the HCHO
column variability
GOME HCHO Temp. anomaly
GOME HCHO Temp. anomaly
1995
1999
1996
2000
2001
1997
Abbot et al. 2003
1998
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RELATING HCHO COLUMNS TO VOC EMISSION
hn (lt345 nm), OH
oxn.
VOCi
HCHO
yield yi
k 0.5 h-1
Emission Ei
smearing, displacement
In absence of horizontal wind, mass balance for
HCHO column WHCHO
Local linear relationship between HCHO and E
but wind smears this local relationship between
WHCHO and Ei depending on the lifetime of the
parent VOC with respect to HCHO production
Isoprene
WHCHO
a-pinene
propane
Distance downwind
100 km
VOC source
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TIME-DEPENDENT HCHO YIELDS FROM VOC OXIDATION
Box model simulations with state-of-science MCM
v3.1 mechanism
methylbutenol
High HCHO signal from isoprene with little
smearing, weak and smeared signal from terpenes
GEOS-Chem yields may be too low by 10-40
depending on NOx
Palmer et al, 2005
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HCHO COLUMN vs. ISOPRENE EMISSION RELATIONSHIPIN
GEOS-Chem MODEL
Results for U.S. quadrants in July 1996
simulation w/ 2ox2.5o horizontal resolution show
(1) dominance of isoprene emission as predictor
of WHCHO variability (2) linear
relationship between the two
Standard simulation
NW
NE
R2 0.43
HCHO from simulation w/o Isoprene emission
R2 0.51
Model HCHO column 1016 molec cm-2
R2 0.65
SE
SW
R2 0.49
We use this relationship to derive top-down
isoprene emissions from the GOME HCHO column
observations
Isoprene emission 1013 atomC cm-2 s-1
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GOME vs. MEGAN ISOPRENE EMISSION INVENTORIES
(2001)
MEGAN is a new inventory of isoprene emissions
developed by Alex Guenther Guenther et al.,
2005

• Good accord for seasonal variation, regional
  distribution of emissions
• GOME 10-34 higher than MEGAN depending on
  month, differences in hot spot locations

Palmer et al. 2005
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EVALUATING GOME ISOPRENE EMISSION ESTIMATES vs.
IN SITU FLUX MEASUREMENTS (2001)
PROPHET forest site in northern Michigan (M.
Pressley, WSU) also shown are local MEGAN
isoperene emission inventory values
Palmer et al. 2005
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YEAR-TO-YEAR VARIABILITY OF GOME HCHO OVER
SOUTHEAST U.S.
Amplitude and phase are highly reproducible
GOME HCHO Column 1016 molec cm-2
Southeast US average 32-38N 100-85W
P. I. Palmer (Harvard)
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WHAT DRIVES GOME HCHO TEMPORAL VARIABILITY OVER
SOUTHEAST U.S. DURING MAY-SEPTEMBER?
Monthly mean GOME HCHO vs. surface air
temperature MEGAN parameterization shown as
fitted curve
Temperature drives 80 of the variance of
monthly mean HCHO columns
P.I. Palmer (Harvard)
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GOME HCHO COLUMNS OVER EAST ASIA (1996-2001)
APR
JAN
JUL
OCT
FEB
MAY
AUG
NOV
MAR
JUN
SEP
DEC
Relationship to VOC emissions far more complex
than for N. America biomass burning, isoprene,
anthropogenic VOCs, direct HCHO emission all
contribute
Tzung-May Fu (Harvard)
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GOME vs. GEOS-Chem HCHO COLUMNS OVER EAST ASIA
MEGAN biogenic emission inventory is far too low
T. M. Fu (Harvard)
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VOC CONTRIBUTIONS TO HCHO PRODUCTION IN CHINESE
CITIES (JAN-FEB 2001)
Vehicle-generated xylenes could make a large
contribution to HCHO columns
NC
CC
Ethane 0.3 Benzene 0.4 Propane 0.3
Toluene 2.4 ALK4 5.1 Xylene 20.2
Ethene 19 Isoprene 8.2 PRPE 43
WC
SC
B. Barletta (UCI), T.-M. Fu (Harvard)
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PRELIMINARY HCHO COLUMN DATA FROM OMI(launched
on Aura in July 2004)
26 Day Average 24 September 19 October 2004
K. Chance and T. Kurosu (Harvard CFA)
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OMI HCHO RETRIEVALS AND MODIS FIRE COUNTS
Chongqing(Red Basin)
Jakarta