1. Retrieval of SO2 Vertical Columns from SCIAMACHY and OMI: Air Mass Factor Algorithm Development and Validation
Chulkyu Lee, Aaron van Dokelaar, Gray O’Byrne: Dalhousie Univ.
Randall V. Martin: Dalhousie Univ. and Harvard-Smithsonian
Nickolay Krotkov: NASA Goddard and UMBC
Andreas Richter: Univ. of Bremen
Greg Huey: Georgia Tech
John S. Holloway: NOAA
May 24, 2009
AGU 2009 Joint Assembly

2. Outline 1 SO2 Measurements from Space 2 Air Mass Factor (AMF) 3
Vertical Columns 3
Comparison & Validation 4
Summary 5

3. SO2 Measurements from Space
TOMS
( )
Total Ozone Mapping Spectrometer
(Kruger et al., 1983, 1995)
GOME
( )
Global Ozone Monitoring Experiment
(Eisinger and Burrows, 1998; Khokhar et al., 2005, 2008; Thomas et al., 2005)
SCIAMACHY
( )
Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (Richter et al., 2006; Lee et al., 2008a, 2008b)
OMI
( )
Ozone Monitoring Instrument
(Krotkov et al., 2006, 2008; Yang et al., 2008)
GOME-2
( )
Global Ozone Monitoring Experiment 2

4. SCIAMACHY and OMI Instrument Satellite platform Launching Year
Equator Crossing Time
Spectral Resolution
Spatial Resolution
Horizontal
(km2)
Global coverage
SCIAMACHY
ENVISAT
2002
10:00 LT
0.25 – 0.4 nm
30×60
6 days
OMI
EOS-Aura
2004
13:30 LT
0.5 nm
13×24
1 day
HIRDLS and MIPAS measure NO2 profile in the upper troposphere

5. Local AMF Calculation Radiative Transfer Model
* Based on Palmer et al., JGR, 2001; Martin et al., JGR, 2002
Geometric AMF:
Radiative Transfer Model
Atmospheric Chemistry Model
Shape factor
SO2 mixing ratio, CSO2(η)
eta (η)
dt(η) Io IB
Earth Surface
Scattering weight
May previous AMFs have assumed a global uniform value.
(η) is temperature-dependent cross-section
Scattering weight
For individual scenes
Calculate ω(η) as function of:
solar and viewing zenith angle (θs, θv)
surface reflectivity, pressure
cloud pressure, aerosol
O3 column:

6. GEOS-Chem Simulation GEOS-Chem v8-01-04
- GEOS-4, 30 η vertical levels, 2º latitude by 2.5º longitude
- Based on EDGAR inventory
- Regional inventories: NEI99, BRAVO, CAC, Streets, EMEP
Update of the eruptive volcanic inventory for 2006 using the database of Global Volcanism Program
(GVP:

7. Shape Factor: GEOS-Chem vs In-situ
Differences would change AMF by <10%
In-situ platform
DC-8 & C-130

8. OMI SO2 AMF for 2006
Calculated at nm; Cloud Radiance Fraction < 0.2; SZA < 70
SCIAMACHY AMF at nm within 25%

9. Local AMF Increases Agreement with Aircraft
▲ INTEX-A
■ INTEX-B

10. SO2 Vertical Columns for 2006
Correlation with
GEOS-Chem (GC)
: Globally r ~0.78
: ~0.84 over US
: ~0.83 over China
GC with OMI AMF
within 10% GC
with SCIAMACHY AMF
Cloud Radiance Fraction < 0.2; SZA < 70

11. AMF error from surface reflectivity, shape factor, aerosol, cloud
Error Analysis
AMF error from surface reflectivity, shape factor, aerosol, cloud
Polluted: SO2 > 1016 molec/cm2
Cloud Radiance Fraction < 0.2; SZA < 70

12. Error Analysis
: 40-55% over the eastern US
: 80% over China

13. Sensitivity of Retrieved SO2 to ΔEmissions
GEOS-Chem SO2
changes by ×2
OMI SO2 AMF
changes < 30%

14. Summary Calculation of local AMFs corrected for aerosol and O3
Validation of GEOS-Chem SO2 shape factors
with airborne in-situ measurements for INTEX-A and B
: <10% change in AMF
Validation of SO2 vertical columns from SCIAMACHY and OMI with airborne in-situ measurements for INTEX-A and B
: r = 0.9
Large signal from surface emissions in retrieved SO2 columns