Aura NO2 talk

1
Ground-level NO2 Concentrations Inferred from OMI

• 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

2
Large Regions Have Insufficient In Situ NO2
Measurements for Air QualityNO2 Toxic Pollutant
Associated with MortalityIn Situ Monitors
Contaminated with Reactive Nitrogen
Highest NO2 maximum quarterly mean by county, 2001
3
OMI Tropospheric NO2 Column Proxy for Surface
Concentration
NO/NO2 ? ? with altitude
4
Tropospheric NO2 Column Strongly Related to
Ground-level Concentration over Land
In Situ GEOS-Chem
Texas AQS
Martin et al., 2004
Eastern North America
New England
In Situ GEOS-Chem
ICARTT
Martin et al., 2006
5
Approach to Infer Surface NO2 from OMI
GEOS-Chem NO2 Profile
OMI Local Information
OMI Tropospheric NO2 Column
i
GEOS-Chem Grid
100 error in GEOS-Chem surface NO2 ? lt 10
error in derived surface NO2 in polluted areas

• S ? Surface NO2
• O ? Tropospheric NO2 column

6
Surface NO2 for 2005 Inferred from OMI (standard
product)
MAM
DJF
SON
JJA
7
Correction for Interference in NO2 in Air
Quality Networks
Difficult issue Loss of HNO3 on stainless steel
of inlet Infer 35
measured from comparison with photolytic converter
Correction Calculated with GEOS-Chem
8
Significant Correlation Between Corrected In Situ
and OMI-derived Surface NO2
Correlation of Concident Observations over 2005
OMI-derived (standard product)
In Situ (corrected) In
Situ (orig)
J F M A M J J A S
O N D
9
Comparison of In Situ and OMI-derived Surface NO2
for 2005Indirect Validation of OMI
DJF MAM
JJA SON
Corrected in situ
OMI-derived (standard)
10
Investigation of Seasonal Bias
- Cannot eliminate by varying HNO3 loss on
inlet - Would need factor of 3-6 seasonal bias in
GEOS-Chem NO2 / NOy to eliminate - Preliminary
consistent seasonal bias vs NO2 from PSS
11
Conclusions
Promising satellite-based surface NO2
estimate Need for additional validation of
surface NO2 with true NO2 Surface
measurements provide indirect validation of NO2
columns
Acknowledgement
Supported by NASA ROSES