RETRIEVAL AND INTERPRETATION OF OZONE PRECURSORS USING THE GOME SATELLITE INSTRUMENT LaRC Air Quality Applications Group Sushil Chandra Jerry Ziemke Randall Martin Kelly Chance Thomas Kurosu Chris Sioris Daniel Jacob Dorian Abbot Paul Palmer Jim Szykman

HOW DO WE EVALUATE AND IMPROVE A PRIORI BOTTOM-UP INVENTORIES? Surface NOX Isoprene during July North American Isoprene Emissions (3-15 Tg C yr-1) Global NOx Emissions (Tg N yr-1) Fossil Fuel 24 (20-33) Biomass Burning 6 (3-13) Soils 5 (4-21) GEIA

TOP-DOWN INFORMATION FROM THE GOME SATELLITE INSTRUMENT Operational since 1995 Nadir-viewing solar backscatter instrument (237-794 nm) Low-elevation polar sun-synchronous orbit, 10:30 a.m. observation time Spatial resolution 320x40 km2, three cross-track scenes Complete global coverage in 3 days

USE GOME MEASUREMENTS TO RETRIEVE NO2 AND HCHO USE GOME MEASUREMENTS TO RETRIEVE NO2 AND HCHO COLUMNS TO MAP NOx AND VOC EMISSIONS GOME Tropospheric NO2 column ~ ENOx Tropospheric HCHO column ~ EVOC BOUNDARY LAYER NO2 NO/NO2   W ALTITUDE NO HCHO CO OH hours hours VOC lifetime <1 day HNO3 Emission Emission NITROGEN OXIDES (NOx) VOLATILE ORGANIC COMPOUND (VOC)

PERFORM A SPECTRAL FIT OF SOLAR BACKSCATTER OBSERVATIONS absorption Solar Io Backscattered intensity IB l1 l2 wavelength Slant optical depth “Slant column” Scattering by Earth surface and by atmosphere EARTH SURFACE

GOME HCHO SLANT COLUMNS (JULY 1996) Hot spots reflect high VOC emissions from fires and biosphere BIOGENIC ISOPRENE IS THE MAIN SOURCE OF HCHO OVER U.S. IN SUMMER K. Chance

SLANT COLUMNS OF NO2 FROM GOME Dominant stratospheric structure (where NO2 is produced from N2O oxidation) Also see tropospheric hot spots (fossil fuel and biomass burning) Remove strat & instrument artifacts using obs over Pacific Martin et al., 2002

SLANT COLUMNS OF TROPOSPHERIC NO2 FROM GOME 1996 Martin et al., 2002

GEOS-CHEM MODEL Assimilated Meteorology (GEOS) 2ox2.5o horizontal resolution, 26 layers in vertical O3-NOx-hydrocarbon chemistry Radiative and chemical effects of aerosols Emissions: Fossil fuel: GEIA (NOx), Logan (CO), Piccot (NMHCs) Biosphere: modified GEIA (hydrocarbons) & Yienger/Levy (soil NOx) Lightning: Price/Rind/Pickering, GEOS convective cloud tops Interannually varying biomass burning Cross-tropopause transport Deposition

IN SCATTERING ATMOSPHERE, AMF CALCULATION NEEDS EXTERNAL INFO ON SHAPE OF VERTICAL PROFILE RADIATIVE TRANSFER MODEL ATMOSPHERIC CHEMISTRY MODEL “a priori” Shape factor dt() Io IB EARTH SURFACE sigma () NO2 mixing ratio CNO2() norm. by column ΩNO2 Scattering weight () is temperature dependent cross-section INDIVIDUAL GOME SCENES Calculate w() as function of: solar and viewing zenith angle surface albedo, pressure cloud optical depth, pressure, frac aerosol profile, type

JULY 1996 Clear-sky NO2 AMF Fraction of IB From Clouds Actual NO2 AMF accounting for clouds Martin et al., 2002

AEROSOLS REDUCE SENSITIVITY OF GOME TO TROPOSPEHRIC NO2 BY UP TO 40% OVER BIOMASS BURNING REGIONS

VERTICAL COLUMNS CONFINED TO REGIONS OF SURFACE EMISSIONS Cloud/albedo artifacts removed by AMF calculation NO/NO2   WITH ALTITUDE NOx lifetime <1day No clear lightning signal Martin et al., 2002

GEOS-CHEM Tropospheric NO2 GOME Tropospheric NO2 GEOS-CHEM Tropospheric NO2 r=0.75 bias 5% Martin et al., 2003 1015 molecules cm-2

STRATEGY: OPTIMIZE INVENTORIES USING A PRIORI BOTTOM-UP AND GOME TOP-DOWN INFORMATION Top-down emissions A priori emissions A posteriori emissions A priori errors Top-down errors Martin et al., 2003

TOP-DOWN ERROR IN NOX EMISSIONS GOME Spectrum (423-451 nm) Spectral fit and removal of stratospheric column 1x1015 molecules cm-2 Tropospheric NO2 Slant Column AMF (surface reflectivity, clouds, aerosols, NO2 profile) 40% of tropospheric column Tropospheric NO2 Column 30% of tropospheric column NOx Lifetime (GEOS-CHEM) NOx Emissions Martin et al., 2003

TOP-DOWN INFORMATION FROM GOME REDUCES ERROR IN NOX EMISSION INVENTORY Bottom-up error a Mean = 2.0 Top-down error t Mean = 2.0 Martin et al., 2003

OPTIMIZED NOX EMISSIONS 36.4 Tg N yr-1 37.7 Tg N yr-1 Martin et al., 2003

DIFFERENCE BETWEEN A POSTERIORI AND A PRIORI Annual mean ratio (A posteriori / A priori) Martin et al., 2003

Dobson Units for March, April, May TOMS/MLS TROPOSPHERIC OZONE CONFIRMS A PRIORI BIOMASS BURNING NOX EMISSIONS HIGH OVER INDIA 30 N Dobson Units for March, April, May TOMS/MLS 30 S 30 N GEOS-CHEM Chandra et al., 2003 30 S

IMPROVE INVENTORIES OF SOIL NOX EMISSIONS GOME Tropospheric NO2 Columns

QUANTIFY INTERANNUAL VARIATION IN NOx EMISSIONS 1997 1998 1999 2000 DJF MAM JJA SON

TEMPORAL VARIATION OF GOME NO2 COLUMNS OFTEN CONSISTENT WITH SURFACE OBSERVATIONS LaRC Air Quality Applications Group and Jim Szykman (EPA)

TROPOSPHERIC NO2 DETERMINED FROM SCIAMACHY BY LIMB-NADIR MATCHING SCIAMACHY Spatial Resolution 7 Times Finer Than GOME

ISOPRENE EMISSIONS FOR JULY 1996 DETERMINED FROM GOME FORMALDEHYDE COLUMNS COMPARE TO… GEIA (IGAC inventory) Palmer et al., 2003

GOME (A posteriori) GEIA (A priori) EVALUATE GOME ISOPRENE INVENTORY BY COMPARISON WITH IN SITU OBSERVATIONS USING GEOS-CHEM MODEL AS INTERMEDIARY CONSISTENT WITH IN-SITU HCHO OBSERVATIONS GEIA (A priori) GOME (A posteriori) r2 = 0.53 r2 = 0.77 Palmer et al., 2003

GEOS-CHEM isoprene emissions (in progress using GBEIS) GOME HCHO COLUMNS SHOW SEASONAL VOC EMISSIONS GOME GEOS-CHEM (GEIA) GOME GEOS-CHEM (GEIA) MAR JUL APR AUG MAY SEP JUN OCT -0.5 0 1016 molec cm-2 2.0 2.5 Agreement in general pattern, regional discrepancies point to need for improving GEOS-CHEM isoprene emissions (in progress using GBEIS) Abbot et al., 2003

HCHO INTERANNUAL VARIATION HIGHLY TEMPERATURE SENSITIVE 1995 1999 1996 2000 2001 1997 1998 Abbot et al., 2003

PRESENT AND FUTURE SATELLITE OBSERVATIONS OF TROPOSPHERIC CHEMISTRY Platform multiple ERS-2 Terra ENVISAT Space station Aura TBD Sensor TOMS AVHRR/SeaWIFS GOME MOPITT MODIS/MISR SCIAMACHY MIPAS SAGE-3 TES OMI MLS CALIPSO OCO Launch 1979 1995 1999 2002 2004 2005 O3 N N/L L CO CO2 NO NO2 HNO3 CH4 HCHO SO2 BrO HCN aerosol Increasing spatial resolution