Aura NO2 talk

1
Estimating Ground-level NO2 Concentrations from
OMI Observations

• Lok Lamsal, Dalhousie University
• Randall Martin, Dalhousie and Harvard-Smithsonian
• Aaron van Donkelaar, Dalhousie University
• Martin Steinbacher, Empa
• Edward Celarier, SGT Inc.
• Eric Bucsela, NASA GSFC
• Edward Dunlea, CIRES
• Joseph Pinto, EPA
• Ruud Dirksen, KNMI
• Folkert Boersma, KNMI

2
Two Major Applications of OMI Tropospheric NO2
Columns
Estimates of Surface Air Quality
Top-down NOx Emissions
Based on PM2.5, O3, and NO2
3
Large Regions Have Insufficient In Situ NO2
Measurements for Air QualityNO2 Associated with
Mortality (Brook et al. 2007) In Situ Monitors
Contaminated with Reactive Nitrogen
Highest NO2 maximum quarterly mean by county, 2001
4
OMI Tropospheric NO2 Column Proxy for Surface
Concentration
NO/NO2 ? ? with altitude
OMI Standard Product October 2004 September
2007 Inclusive
5
Strong Correlation Between Modeled NO2 Column and
Surface NO2 Concentration
Simulated Concentrations (GEOS-Chem) over North
America
Day (March 5, 2005)
Annual Mean (2005)
r20.96 n652
r20.86 n652
6
Promising Relationship Between Modeled and
In-Situ NO2 Profiles
In Situ GEOS-Chem
Texas AQS
Martin et al., 2004
Eastern North America
New England
In Situ GEOS-Chem
ICARTT
Martin et al., 2006
7
General Approach to Estimate Surface NO2
Coincident Model NO2 Profile
Daily OMI Tropospheric NO2 Column

• S ? Surface NO2
• O ? Tropospheric NO2 column

8
Specific Approach to Estimate Surface NO2 Use
OMI to Infer Sub-Grid Variation in NO2 Profile
OMI (2o x 2.5o)
OMI (0.1o x0.1o)
Tropospheric NO2 Column (1015 molec cm-2)
?O
S ? Surface NO2 O ? Tropospheric NO2 column OF ?
Free tropospheric NO2
Specific approach changes result by 10-30
9
Surface NO2 for 2005 Inferred from OMI
MAM
DJF
SON
JJA
10
Sample Comparison of In-situ and
OMI-derived Surface NO2
11
Significant Correlation Between In Situ and
OMI-derived Surface NO2
Near-Real-Time
Standard Product
Correlation of Coincident Observations over 2005
12
Comparison of In Situ and OMI-derived Surface NO2
for 2005Indirect Validation of OMI
DJF MAM
JJA SON
OMI (STD) r0.76
OMI (NRT) r0.78
In situ
13
Seasonal Comparison by Land Type
14
Conclusions
Promising satellite-based surface NO2
estimate Surface measurements provide indirect
validation of NO2 columns Need to understand
seasonal differences
Future Directions
High resolution profile information (nested and
regional models)Evaluate with ground-based
measurements of true NO2More sophisticated
algorithms for emission inversions (i.e. adjoint)
Supported by NASA and NSERC