SATELLITE OBSERVATIONS OF ATMOSPHERIC CHEMISTRY

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SATELLITE OBSERVATIONS OF ATMOSPHERIC CHEMISTRY
Daniel J. Jacob
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OBSERVATION BY SOLAR OCCULTATION
satellite sunrise
Tangent point retrieve vertical profile of
concentrations
EARTH
Recent extensions to lunar and stellar occultation
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OBSERVATION BY THERMAL EMISSION (IR, mwave)
NADIR VIEW
LIMB VIEW
elIl(T1)
Absorbing gas or aerosol
T1
Il(To)
To
EARTH SURFACE
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OBSERVATION BY SOLAR BACKSCATTER (UV-IR)
Absorption/ scattering by Earth surface and
atmosphere
ATMOSPHERE
EARTH SURFACE
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TOMS OBSERVATION OF ANTARCTIC OZONE HOLEExample
of observation by solar backscatter
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MOST OBSERVATIONS OF ATMOSPHERIC COMPOSITION FROM
SPACE HAVE BEEN FOR THE STRATOSPHERE

• Observation of troposphere
• is far more difficult because of
• clouds
• particles (dust)
• water vapor continuum
• strat ozone layer

Mesosphere
Stratosphere
Ozone layer
Troposphere
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PRESENT AND FUTURE SATELLITE MEASUREMENTS FOR
TROPOSPHERIC CHEMISTRY
2002 2002 2004 2004 2004 2004
2004
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ATMOSPHERIC CHEMISTRY MODELS AND SATELLITE
OBSERVATIONS THE ODD COUPLE
SATELLITE SPECTRA L1 DATA
CLIMATOLOGICAL IN SITU OBSERVATIONS
A PRIORI INFORMATION vertical gradient, concentrat
ion range, correlations
RETRIEVAL
ATMOSPHERIC CONCENTRATIONS L2 DATA
ATMOSPHERIC CHEMISTRY MODELS
INCEST?
EVALUATION ASSIMILATION
SCIENTIFIC ANALYSIS L4 DATA
INCREASED KNOWELDGE
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GEOS-CHEM global model of tropospheric
chemistry(www-as.harvard.edu/chemistry/trop/geos)

• Driven by NASA GEOS assimilated meteorological
  data, 1988-2001
• 1ox1o- 4ox5o horizontal resolution, 20-48 layers
  in vertical
• Simulation of tropospheric ozone-NOx-hydrocarbon
  chemistry includes 80 interacting species

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THE GOME SATELLITE INSTRUMENT

• Nadir-viewing solar backscatter instrument
  (237-794 nm)
• Low-elevation polar sun-synchronous orbit, 1030
  a.m. observation time
• Field of view 320x40 km2, three cross-track
  scenes
• Complete global coverage in 3 days

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USE GOME MEASUREMENTS OF NO2 AND HCHO COLUMNSTO
MAP NOxAND VOC EMISSIONS
GOME
Tropospheric NO2 column ENOx Tropospheric HCHO
column EVOC
2 km
hn (420 nm)
hn (340 nm)
BOUNDARY LAYER
NO2
NO
HCHO
OH
CO
hours
O3, RO2
hours
VOC
1 day
HNO3
Emission
Emission
Deposition
NITROGEN OXIDES (NOx)
VOLATILE ORGANIC CARBON (VOC)
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COLUMN MEASUREMENT OF AN ABSORBING GAS USING
SOLAR BACKSCATTER
absorption
l1
l2
wavelength
Slant optical depth
Slant column
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SLANT COLUMNS OF HCHO FROM GOMEHigh values over
southeast U.S. are due to biogenic isoprene
emission
Palmer et al. 2002
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SLANT COLUMNS OF NO2 FROM GOMEDominant
stratospheric contribution (NO2 produced from N2O
oxidation)Also see tropospheric hot spots
(fossil fuel and biomass burning)
Remove stratospheric column and instrument
artifacts using data over Pacific
Martin et al. 2002
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SLANT COLUMNS OF TROPOSPHERIC NO2 FROM GOME
1996
Martin et al. 2002
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AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN WS
TO VERTICAL COLUMN W
Geometric AMF (AMFG) for non-scattering
atmosphere
q
EARTH SURFACE
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IN SCATTERING ATMOSPHERE, AMF DEPENDS ON SHAPE OF
VERTICAL PROFILE (FOR WHICH GOME PROVIDES NO
INFORMATION)
AMFG 2.08 actual AMF 0.71
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CALCULATE AMF FOR EVERY GOME SCENEUSING LOCAL
SHAPE FACTORS FROM GEOS-CHEM
GOME efficiency f (sun angle, albedo, cloud)
Vertical concentration profile shape factor
Geometric AMF
RADIATIVE TRANSFER MODEL
ATMOSPHERIC CHEMISTRY MODEL (GEOS-CHEM)
From GOME
Slant column
Vertical column
AMF
From model
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COMPARE MODEL VERTICAL PROFILES OF HCHOTO (THE
FEW!) AVAILABLE AIRCRAFT OBSERVATIONS
SOS (southeast U.S., Jul 1995)
NARE (N. Atlantic, Sept 1997)
Observations
Model
Palmer et al. 2001
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DIAGNOSE MODEL CONTAMINATION OF RETRIEVALBY
CORRELATING AMF WITH VERTICAL COLUMN
r -0.65
r -0.14
Negative correlation implies that AMF conversion
to vertical columns will modify the slant column
patterns to better fit the model
Martin et al. 2002
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PROPAGATION OF ERRORS IN NO2 RETRIEVAL (errors
e in 1015 molecules cm-2)
Fit spectrum
e1 0.8

• Use Central Pacific GOME data with
• HALOE to test strat zonal invariance
• PEM-Tropics, GEOS-CHEM 3-D model to treat
  tropospheric residual

Remove stratospheric contribution, diffuser plate
artifact
e2 0.4

• Use radiative transfer model with
• local vertical shape factors from GEOS-CHEM
• local cloud information from CRAG

Apply AMF to convert slant column to vertical
column
e3 0.5-3.2
Martin et al. 2002
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CAN WE USE GOME TO ESTIMATE NOx EMISSIONS?TEST
IN U.S. WHERE GOOD A PRIORI EXISTS
Comparison of GOME retrieval (July 1996) to
GEOS-CHEM model fields using EPA emission
inventory for NOx
GOME
GEOS-CHEM (EPA emissions)
BIAS 3 R 0.79
R 0.78 Bias 18
Martin et al. 2002
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GOME RETRIEVAL OF TROPOSPHERIC NO2vs. GEOS-CHEM
SIMULATION (July 1996)
Martin et al. 2002
GEIA emissions scaled to 1996
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FORMALDEHYDE COLUMNS FROM GOMEJuly 1996 means
Palmer et al. 2001
BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO IN
U.S. IN SUMMER
GEIA isoprene emissions
R 0.83 Bias 14
Precision 4x1015 cm-2
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MODEL AS INTERMEDIARY FOR GOME VALIDATIONEVALUAT
E AGAINST IN SITU SURFACE OBSERVATIONS
Mean daytime HCHO surface observations Jun-Aug
1988-1998
Model (1996) vs. observations
Palmer et al. 2002
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GOME DETECTS THE ISOPRENE VOLCANO IN THE OZARKS
Palmer et al. 2002
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DEPENDENCE OF GOME HCHO COLUMNSOVER THE OZARKS
ON SURFACE AIR TEMPERATURE
Temperature dependence of isoprene emission (GEIA)
Palmer et al. 2002
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YIELD OF HCHO FROM ISOPRENE OXIDATION
isoprene
OH
1 hour
O2
OO.
days
OH
NO
NO2
GEOS-CHEM mechanism
HCHO HO2
O
methylvinylketone
Palmer et al. 2002
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GEOS-CHEM RELATIONSHIP BETWEEN HCHO COLUMNS AND
ISOPRENE EMISSIONS IN N AMERICAUse relationship
to map isoprene emissions from GOME observations
NW
NE
GEOS-CHEM July 1996
Model HCHO column 1016 molec cm-2
SE
SW
model without isoprene
Palmer et al. 2002
Isoprene emission 1013 atomC cm-2 s-1
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MAPPING OF ISOPRENE EMISSIONS FOR JULY 1996 BY
SCALING OF GOME FORMALDEHYDE COLUMNS Palmer et
al., 2002
GOME
COMPARE TO
GEIA (IGAC inventory)
BEIS2 (official EPA inventory)
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NEXT STEP GLOBAL MAPPING OF VOC EMISSIONS FROM
SPACE!
T. Kurosu (SAO) and P. Palmer (Harvard)
T. Kurosu (SAO) and P.I. Palmer (Harvard)