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”

AIR MASS FACTOR (AMF) CONVERTS AIR MASS FACTOR (AMF) CONVERTS SLANT COLUMN SLANT COLUMN SS TO VERTICAL COLUMN TO VERTICAL COLUMN

“Geometric AMF” (AMFG) for non-scattering atmosphere:

EARTH SURFACE

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

( ) ( )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

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

NITROGEN OXIDES (NOx) VOLATILE ORGANIC CARBON (VOC)

Emission

OHHCHOh (340 nm)

hoursCO

BOUNDARYLAYER

~ 2 km

Tropospheric NO2 column ~ ENOx

Tropospheric HCHO column ~ EVOC

Deposition

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

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

SOS (southeast U.S., Jul 1995)

NARE (N. Atlantic, Sept 1997)

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

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)

USING GOME HCHO COLUMNS USING GOME HCHO COLUMNS TO MAP ISOPRENE EMISSIONSTO MAP ISOPRENE EMISSIONS

isoprene

HCHOhours

OH h, OH

Displacement/smearing length scale 10-100 km

HCHO HCHOISOP

ISOP HCHO

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

GEOS-CHEMJuly 1996

Isoprene emission [1013 atomC cm-2 s-1]

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)

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

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

GOME RETRIEVAL OF TROPOSPHERIC NOGOME RETRIEVAL OF TROPOSPHERIC NO22

vs. GEOS-CHEM SIMULATION (July 1996)vs. GEOS-CHEM SIMULATION (July 1996)

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

GEOS-CHEM(EPA emissions)

BIAS = +3%

R = 0.79

R = 0.78Bias = +18%

MEASUREMENT OF TROPOSPHERIC COMPOSITION FROM SPACE IS DIFFICULT!

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