MEASUREMENT OF TROPOSPHERIC COMPOSITION FROM SPACE IS DIFFICULT!
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MEASUREMENT OF TROPOSPHERIC COMPOSITION MEASUREMENT OF TROPOSPHERIC COMPOSITION FROM SPACE IS DIFFICULT!FROM SPACE IS DIFFICULT!
Tropopause
Stratopause
•clouds• particles (dust)• air scattering• water vapor •strat ozone layer• variable surf. albedo• low thermal contrast
Stratosphere
Troposphere
Ozonelayer
Mesosphere
2002 2002 2004 2004 2004 2004 2004
PRESENT AND SCHEDULED SATELLITE INSTRUMENTS PRESENT AND SCHEDULED SATELLITE INSTRUMENTS FOR TROPOSPHERIC CHEMISTRYFOR TROPOSPHERIC CHEMISTRY
SOLAR BACKSCATTER OBSERVATIONS FROM SPACESOLAR BACKSCATTER OBSERVATIONS FROM SPACE(TOMS, GOME, SCIAMACHY, OMI, OCO)(TOMS, GOME, SCIAMACHY, OMI, OCO)
absorption
wavelength
Slant optical depth
EARTH SURFACE
Scattering by Earth surface and by atmosphere
Backscatteredintensity IB
“Slant column”
])(
)(ln[
1
2
B
BS I
I
SeffS
AIR MASS FACTOR (AMF) CONVERTS AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN SLANT COLUMN SS TO VERTICAL COLUMN TO VERTICAL COLUMN
SAMF
“Geometric AMF” (AMFG) for non-scattering atmosphere:
EARTH SURFACE
cos
cos1GAMF
Instrumentsensitivity w()(“scattering weight”)
Vertical shapefactor S()(normalized mixing ratio)
what GOMEsees
AMFG = 2.08actual AMF = 0.71
IN SCATTERING ATMOSPHERE, IN SCATTERING ATMOSPHERE, AMF DEPENDS ON VERTICAL DISTRIBUTION OF COLUMNAMF DEPENDS ON VERTICAL DISTRIBUTION OF COLUMN
1
0
( ) ( )GAMF AMF w S d
Illustrative retrieval of HCHO column at 340 nm“Sigma” vertical coordinate = normalized pressure
Palmer et al. [2001]
USE GLOBAL 3-D MODEL DRIVEN BY ASSIMILATED USE GLOBAL 3-D MODEL DRIVEN BY ASSIMILATED METEOROLOGICAL DATA TO PROVIDE AMFsMETEOROLOGICAL DATA TO PROVIDE AMFs
FOR EVERY SATELLITE VIEWING SCENE FOR EVERY SATELLITE VIEWING SCENE
SATELLITE DATA
SLANTCOLUMN
GEOS-CHEMMODEL
AMF
VERTICALCOLUMN
VERTICALCOLUMN
• Best information applied to each scene• Consistency in comparing model and observed columns• Apply with any 3-D model (recalculate AMFs using tabulated scattering weights)
ADVANTAGES OF 3-D MODEL APPROACHFOR COMPUTING AMFs
spectralfit
LIDORT RAD.TRANSFER MODEL
THE GOME SATELLITE INSTRUMENTTHE GOME SATELLITE INSTRUMENT
• Nadir-viewing solar backscatter instrument (237-794 nm)
• Low-elevation polar sun-synchronous orbit, 10:30 a.m. observation time
• Field of view 320x40 km2, three cross-track scenes
• Complete global coverage in 3 days
• Operational since 1995
APPLY HERE TO MAPPING OF HCHO AND NO2 TROPOSPHERIC COLUMNS
USE GOME MEASUREMENTS OF NOUSE GOME MEASUREMENTS OF NO22 AND HCHO COLUMNS AND HCHO COLUMNS
TO MAP NOTO MAP NOxxAND VOC EMISSIONSAND VOC EMISSIONS
Emission
NOh (420 nm)
O3, RO2
NO2
HNO3
1 day
NITROGEN OXIDES (NOx) VOLATILE ORGANIC CARBON (VOC)
Emission
VOC
OHHCHOh (340 nm)
hoursCO
hours
BOUNDARYLAYER
~ 2 km
Tropospheric NO2 column ~ ENOx
Tropospheric HCHO column ~ EVOC
Deposition
GOME
T. Kurosu (SAO) and P. Palmer (Harvard)
T. Kurosu, P.I. Palmer
GOME HCHO SLANT COLUMNS (JULY 1996) GOME HCHO SLANT COLUMNS (JULY 1996)
Hot spots reflect high VOC emissions from fires and biosphere
HCHO COLUMNS FROM GOME OVER U.S.:HCHO COLUMNS FROM GOME OVER U.S.:July 1996 meansJuly 1996 means
BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO IN U.S. IN SUMMER
Palmer et al. [2001]
GEIAisopreneemissions
R = 0.83Bias 14%
Precision:4x1015 cm-2
STRATEGY FOR GOME VALIDATION: STRATEGY FOR GOME VALIDATION: USE 3-D MODEL AS INTERMEDIARYUSE 3-D MODEL AS INTERMEDIARY
GOME OBSERVATIONSIN SITU OBSERVATIONS
• Aircraft• Ground-based
GEOS-CHEMmodel
Compare Compare
Observations
Model
SOS (southeast U.S., Jul 1995)
NARE (N. Atlantic, Sept 1997)
Palmer et al. [2001]
Aircraft observations from Y.-N. Lee (SOS) and A. Fried (NARE)
MODEL vs. OBSERVED HCHO VERTICAL PROFILES MODEL vs. OBSERVED HCHO VERTICAL PROFILES OVER U.S. AND N. ATLANTICOVER U.S. AND N. ATLANTIC
MODEL vs. OBSERVED SURFACE HCHOMODEL vs. OBSERVED SURFACE HCHO
Mean daytime HCHO surface observationsJun-Aug 1988-1998 Model (1996) vs. observations
Palmer et al. [2002]
SLANT COLUMNS OF HCHO FROM GOMESLANT COLUMNS OF HCHO FROM GOMEHigh values over southeast U.S. are due to biogenic isoprene emissionHigh values over southeast U.S. are due to biogenic isoprene emission
Palmer et al. [2002]Note “isoprene volcano” over the Ozarks
DEPENDENCE OF GOME HCHO COLUMNSDEPENDENCE OF GOME HCHO COLUMNSOVER THE OZARKS ON SURFACE AIR TEMPERATUREOVER THE OZARKS ON SURFACE AIR TEMPERATURE
Temperature dependenceof isoprene emission (GEIA)
Palmer et al. [2002]
USING GOME HCHO COLUMNS USING GOME HCHO COLUMNS TO MAP ISOPRENE EMISSIONSTO MAP ISOPRENE EMISSIONS
isoprene
HCHOhours
OH h, OH
hours
Displacement/smearing length scale 10-100 km
HCHO HCHOISOP
ISOP HCHO
kE
Yield
Get EISOP vs. HCHO relationship from GEOS-CHEM
GEOS-CHEM RELATIONSHIP BETWEEN HCHO COLUMNS GEOS-CHEM RELATIONSHIP BETWEEN HCHO COLUMNS AND ISOPRENE EMISSIONS IN N AMERICAAND ISOPRENE EMISSIONS IN N AMERICA
Use relationship to map isoprene emissions from GOME observationsUse relationship to map isoprene emissions from GOME observations
Palmer et al. [2002]
GEOS-CHEMJuly 1996
NW NE
SESW
Isoprene emission [1013 atomC cm-2 s-1]
Mod
el H
CH
O c
olu
mn
[101
6 m
ole
c c
m-2
]
model without isoprene
MAPPING OF ISOPRENE MAPPING OF ISOPRENE EMISSIONS FOR JULY 1996 EMISSIONS FOR JULY 1996 BY SCALING OF GOME BY SCALING OF GOME FORMALDEHYDE COLUMNS FORMALDEHYDE COLUMNS [Palmer et al., 2002][Palmer et al., 2002]
GEIA (IGAC inventory)
BEIS2(official EPA inventory)
GOME
COMPARE TO…
SLANT COLUMNS OF NOSLANT COLUMNS OF NO22 FROM GOME FROM GOMEDominant stratospheric contribution (NODominant stratospheric contribution (NO22 produced from N produced from N22O oxidation)O oxidation)
Also see tropospheric hot spots (fossil fuel and biomass burning)Also see tropospheric hot spots (fossil fuel and biomass burning)
Martin et al. [2002a]
Remove stratospheric column and instrument artifacts using data over Pacific
SLANT COLUMNS OF TROPOSPHERIC NOSLANT COLUMNS OF TROPOSPHERIC NO22 FROM GOME FROM GOME
1996
Martin et al. [2002]
PROPAGATION OF ERRORS IN NOPROPAGATION OF ERRORS IN NO22 RETRIEVAL RETRIEVAL
(errors (errors in 10in 101515 molecules cm molecules cm-2-2))
GOME SPECTRUM (423-451 nm)
SLANT NO2 COLUMN
TROPOSPHERIC SLANT NO2 COLUMN
TROPOSPHERIC NO2 COLUMN
Fit spectrum
Remove stratospheric contribution, diffuser plate artifact
Use Central Pacific GOME data with:•HALOE to test strat zonal invariance•PEM-Tropics, GEOS-CHEM 3-D model to treat tropospheric residual
Apply AMF to convert slant column to vertical column
Use radiative transfer model with:• local vertical shape factors from GEOS-CHEM• local cloud information from CRAG
Martin et al. [2002a]
GOME RETRIEVAL OF TROPOSPHERIC NOGOME RETRIEVAL OF TROPOSPHERIC NO22
vs. GEOS-CHEM SIMULATION (July 1996)vs. GEOS-CHEM SIMULATION (July 1996)
Martin et al. [2002a]
GEIA emissionsscaled to 1996
CAN WE USE GOME TO ESTIMATE NOCAN WE USE GOME TO ESTIMATE NOx x EMISSIONS?EMISSIONS?
TEST IN U.S. WHERE GOOD TEST IN U.S. WHERE GOOD A PRIORI A PRIORI EXISTS EXISTSComparison 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
Martin et al. [2002a]
R = 0.78Bias = +18%