1. Constraining Emissions with Satellite Observations
Daniel Jacob Paul Palmer Dorian Abbot
Randall Martin Kelly Chance Thomas Kurosu
Sushil Chandra Jerry Ziemke

2. PRESENT AND FUTURE SATELLITE OBSERVATIONS OF TROPOSPHERIC CHEMISTRY
HCHO

3. CHALLENGE FOR THE NEXT DECADE: IMPROVE EMISSION INVENTORIES
“Nova Scotians with lung problems should stay inside until pollution levels drop warned Environment Canada”

4. Historical records imply a large anthropogenic contribution to the present-day ozone background at northern midlatitudes
Ozone trend from European mountain observations,
[Marenco et al.,1994]
Major greenhouse gas
Largely controls atmospheric oxidation
Primary constituent of smog

5. ? ? ? GLOBAL BUDGET OF TROPOSPHERIC OZONE 4900 4200 500 1200
Global sources and sinks, Tg O3 yr-1 (GEOS-CHEM model)
Chem prod in troposphere
4900
Chem loss in troposphere
4200
Transport from stratosphere
500
Deposition
1200 ?
Formaldehyde (HCHO) ? ? hv
hv,H2O
Nitrogen oxides (NOx)
CO, VOCs
Ozone (O3)
Hydroxyl (OH)
Fires
Biosphere
Human
activity

6. BOTTOM-UP EMISSION INVENTORIES ARE NOTORIOUSLY DIFFICULT TO DETERMINE!
Fuel use estimates
Measurements of emission ratios
Process studies
Estimate biological density
Temperature, water, … dependence of biological activity
Extreme events
"Trees cause more pollution than automobiles do."

7. HOW DO WE EVALUATE AND IMPROVE A PRIORI BOTTOM-UP INVENTORIES?
Surface NOX
Isoprene during July
GEIA

8. TOP-DOWN INFORMATION FROM THE GOME SATELLITE INSTRUMENT
Operational since 1995
Nadir-viewing solar backscatter instrument ( 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

9. 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)

10. 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

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

12. 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

13. SLANT COLUMNS OF TROPOSPHERIC NO2 FROM GOME
1996

14. 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

15. 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

16. VERTICAL COLUMNS CONFINED TO REGIONS OF SURFACE EMISSIONS Cloud artifacts removed by AMF calculation
NO/NO2  
WITH ALTITUDE
NOx lifetime
<1day

17. GEOS-CHEM Tropospheric NO2
GOME Tropospheric NO2
GEOS-CHEM Tropospheric NO2
r=0.75 bias 5%
1015 molecules cm-2

18. STRATEGY: OPTIMIZE INVENTORIES USING A PRIORI BOTTOM-UP AND GOME TOP-DOWN INFORMATION
Retrieved emissions
A priori emissions
A posteriori emissions
A priori errors
Retrieval errors

19. TOP-DOWN ERROR IN NOX EMISSIONS
GOME Spectrum ( nm)
Spectral fit and removal of stratospheric column
1x1015 molecules cm-2
Tropospheric NO2 Slant Column
AMF (surface reflectivity, clouds, aerosols, NO2 profile)
42% of tropospheric column
Tropospheric NO2 Column
30% of tropospheric column
NOx Lifetime (GEOS-CHEM)
NOx Emissions

20. TOP-DOWN INFORMATION FROM GOME REDUCES ERROR IN NOX EMISSION INVENTORY
Bottom-up error a
Top-down error r

21. OPTIMIZED NOX EMISSIONS

22. DIFFERENCE BETWEEN A POSTERIORI AND A PRIORI
Annual mean ratio (A posteriori / A priori)

23. TROPOSPHERIC OZONE DETERMINED FROM TOMS/MLS SUGGESTS A PRIORI NOX EMISSIONS HIGH OVER INDIA
Dobson Units for March, April, May
TOMS/MLS Chandra et al. [2003]
GEOS-CHEM

24. ISOPRENE EMISSIONS FOR JULY 1996 DETERMINED BY SCALING GOME FORMALDEHYDE COLUMNS
COMPARE TO…
GEIA (IGAC inventory)
[Palmer et al., 2003]

25. 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

26. GOME HCHO COLUMNS SHOW SEASONAL EVOLUTION OF VOC EMISSIONS
D. Abbot
APR
JUL
MAY
AUG
JUN
SEP

27. TOP-DOWN INFORMATION FROM GOME IMPROVES BOTTOM-UP INVENTORIES Higher spatial resolution provided by SCIAMACHY