Folkert Boersma Collaborators: Daniel J. Jacob, Miri Trainic, Yinon Rudich, Ruud Dirksen, and Ronald van der A Comparison of NO Comparison of NO 2 air pollution in air pollution in Israeli cities measured from the Israeli cities measured from the ground and from SCIAMACHY and OMI ground and from SCIAMACHY and OMI Dutch OMI NO 2 product DOMINO (www.temis.nl)
Dutch OMI NO 2 product DOMINO (www.temis.nl). Folkert Boersma. Collaborators: Daniel J. Jacob, Miri Trainic, Yinon Rudich, Ruud Dirksen, and Ronald van der A. Comparison of NO 2 air pollution in Israeli cities measured from the ground and from SCIAMACHY and OMI. Motivation. - PowerPoint PPT Presentation
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Folkert BoersmaCollaborators: Daniel J. Jacob, Miri Trainic, Yinon Rudich, Ruud Dirksen, and Ronald van der A
Comparison of NOComparison of NO22 air pollution in Israeli cities air pollution in Israeli cities
measured from the ground and from measured from the ground and from SCIAMACHY and OMISCIAMACHY and OMI
Dutch OMI NO2 product
DOMINO (www.temis.nl)
Motivation
Trends in emissions• Can we use satellite measurements of NO2 to obtain better estimates of NOx emissions?
Monitoring of a target polluter• Is tropospheric NO2 a proxy for near-surface NO2?
Boersma et al., Atmos. Environ., 2008
Comparison of surface and satellite NO2
Different quantities and error budgets:• near-surface concentrations vs. trop. columns• point measurements vs. spatial average• interference from NOz vs. AMF errors
BUT: • Validation still sparse, especially on larger spatial and longer temporal scales• Allows for validation of diurnal cycle
Interference
• Ground-based instruments with molybdenum converter overestimate NO2 • Interference from HNO3, PAN, alkyl nitrates• Effect largest in summer (photochemistry) for regions downwind of sources
Schaub et al., ACP, 2006
• 8 urban stations in Israel8 urban stations in Israel
• Half-hourly NOHalf-hourly NO22 & O & O33 concentrations concentrations
• Molybdenum convertersMolybdenum converters
Known issues with in situ NO2Summarize Dunlea et al.Dunlea et al.,
(ACP, 2007)
• Very little interference at 10:00 (fresh emissions, little photochemical processing yet)
• Interference modest at 13:30
• Interference correlates with ambient O3 concentration, but O3 itself does not represent an interference
What does this mean for urban, in situ NO2 ?
slope = 0.1
Israeli cities: no specific NO2 measurements available, but we have in-situ observed O3
O3 = O3[13:30] – O3[10:00]
• Dunlea et al.: interference = 0.1 O3
• Two limiting cases: – no correction at all
– correcting NO2 at 13:45 as follows:
Interference correction based on in situ O3
slope = 0.09 slope = 0.24
slope = 0.10
Δlat,lon < 0.1°
OMI VZA < 35°
fclrad < 50%
No correction
Δlat,lon < 0.1°
OMI VZA < 35°
fclrad < 50%
r = 0.61 (n=396)RMA: y = -1.28 + 0.90x
No correction
Δlat,lon < 0.1°
OMI VZA < 35°
fclrad < 50%
r = 0.54 (n=396)RMA: y = -0.68 + 0.92x
Uniform correction (-8%)
• Assume well-mixed boundary-layer
• Extrapolate surface NO2 throughout the BL depth
• Seasonal variation in noontime BL depths over Israel from Dayan et al. [1988, 2002]
Boundary-layer columns from surface NO2
1091
790
608
DJF
MAM, SON
JJA
NO2 (ppb)
z (m)
Summertime subtropical high is associated with subsidence of FT air, “capping” the BL.