sensitivity of surface ozone to nitrogen oxides and volatile organic compounds arlene fiorerandall...
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Sensitivity of Surface Ozone to Nitrogen Oxides andSensitivity of Surface Ozone to Nitrogen Oxides andVolatile Organic CompoundsVolatile Organic Compounds
Arlene FioreRandall Martin
Aaron Van Donkelaar
Surface Ozone Remains a Major Issue Surface Ozone Remains a Major Issue Half of All Canadians and Half of All Americans Live In Regions that Fail Half of All Canadians and Half of All Americans Live In Regions that Fail
to Achieve their Ozone Air Quality Standardsto Achieve their Ozone Air Quality Standards(Ozone impairs respiration, reduces crop yields, oxidizes materials)(Ozone impairs respiration, reduces crop yields, oxidizes materials)
Observed Peak Surface Ozone Concentration For a “Typical” Episode Observed Peak Surface Ozone Concentration For a “Typical” Episode
1-hour Average Peak Concentration
0-60 ppb
61-79 ppb
80-99 ppb
100-110 ppb
111-124 ppb
125+ ppb
Surface Ozone is Highly Sensitive to Climate ChangeSurface Ozone is Highly Sensitive to Climate ChangeOzone-Temperature Relationship Observed over 1980-1998Ozone-Temperature Relationship Observed over 1980-1998
Probability of max 8-h O3 > 84 ppbvvs. daily max. T
# summer days with 8-hour O3 > 84 ppbv,average for northeast U.S. sites
Lin et al. [Atm. Env. 2001]
1988, hottest on record!
?
Tropospheric Ozone
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
•Primary constituent of smog
•Major greenhouse gas
•Largely controls atmospheric oxidation
Global Budget of Tropospheric Ozone
CO, VOCs, NOx
HO2OH
NONO2
H2O2
O3
hv, H2O
hvHNO3
OH
VOCs + OH HCHO
HCHO + h 2HO2 + CO
HCHO + OH HO2 + CO + H2O
CO, VOCs
Simplified Tropospheric Ozone (O3) Chemistry
Role of Formaldehyde (HCHO)
NOx
HOx
Insignificant Trend (1980-1995) in Observed Summer Insignificant Trend (1980-1995) in Observed Summer Afternoon Ozone Over Most of the United States despite 12% Afternoon Ozone Over Most of the United States despite 12%
decrease in VOC emissions (no change in NOdecrease in VOC emissions (no change in NOxx emissions) emissions)
Decreasing trend in major metropolitan centersDecreasing trend in major metropolitan centers
Fiore et al., JGR, 1998
Dependence of Ozone Production on NODependence of Ozone Production on NOxx and VOCs and VOCs
HOx family = OH + HO2 + RO + RO2
OH
RO2 RO
HO2
HNO3 H2O2O3
O3
O3
PHOx
1
2
34
56
“NOx- saturated” or“VOC-limited” regime
“NOx-limited” regime
VOC
NO
O2
NO
NO2
HCHO
]][[
][2)(
26
13 MNOk
VOCPkOP xHO ][2)(
5.0
543 NOk
PkOP HOx
][
][2
26
1
NOk
VOCkOPE
Ozone Control Strategies Require Independent Ozone Control Strategies Require Independent Information on Effectiveness of Reducing NOInformation on Effectiveness of Reducing NOxx or VOCs or VOCs
Would like to observe this transition from space
Can observe tropospheric NO2 and HCHO columns . . .
Sillman introduced the concept of NOx-VOC indicators, i.e. H2O2/HNO3 and HCHO/NOy (NOy = total reactive nitrogen)
Sillman, JGR, 1995
Predicted reduction in peak (afternoon) ozone for a 35% decrease in NOx and VOC emissions
VOC
HCHO strongly correlated with HOx source & VOC oxidation
NOx-limitedNOx-saturated
Diagnose Indicators with GEOS-CHEM ModelDiagnose Indicators with GEOS-CHEM Model• Assimilated Meteorology (GEOS)
• 4ox5o horizontal resolution, 20 layers in vertical
• O3-NOx-VOC chemistry
• Radiative and chemical effects of aerosols
• Anthropogenic and natural emissions
• Cross-tropopause transport
• Deposition
Bey et al., JGR, 1999
Martin et al., JGR, 2002a
Calculated Mean Surface Ozone for August 1997
Conduct Three SimulationsConduct Three Simulations• Base Case
• Reduce Anthropogenic NOx Emissions by 50%
• Reduce Anthropogenic VOC Emissions by 50%
Fiore et al., JGR, 2002
Tropospheric HCHO/NOTropospheric HCHO/NO22 Column Ratio Is an Indicator of the Sensitivity of Column Ratio Is an Indicator of the Sensitivity of
Afternoon Surface Ozone to NOAfternoon Surface Ozone to NOxx and VOC Emissions and VOC Emissions
GEOS-CHEM Model Calculation For Polluted Regions, Mar-NovGEOS-CHEM Model Calculation For Polluted Regions, Mar-Nov
NOx Limited
NOx SaturatedNOx Titration
Tropospheric NOTropospheric NO22 and HCHO Columns Largely Confined Near the Surface and HCHO Columns Largely Confined Near the Surface
Also Closely Related to NOAlso Closely Related to NOx x and VOC Emissionsand VOC Emissions
Emission
NO NO2
HNO3
hours
Nitrogen Oxides (NOx) Volatile Organic Compounds (VOC)
Emission
VOC
OHHCHO hoursCO
hours
Boundary Layer
NO/NO2
W ALTITUDE
Tropospheric NO2 column ~ ENOx
Tropospheric HCHO column ~ EVOC
HO2
Surface ozone concentrations are sensitive to the Surface ozone concentrations are sensitive to the ratio of NOratio of NOxx emissions to VOC emissions emissions to VOC emissions
Sillman and He, 2002
(ppbv)
Retrieve Tropospheric NORetrieve Tropospheric NO22 and HCHO From the and HCHO From the
GOME Satellite InstrumentGOME Satellite Instrument•Operational since 1995
•Nadir-viewing solar backscatter instrument (237-794 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
Perform a Spectral Fit of Solar Backscatter ObservationsPerform a Spectral Fit of Solar Backscatter Observations
absorption
wavelength
Slant optical depth
EARTH SURFACE
Scattering by Earth surface and by atmosphere
Backscatteredintensity IB
“Slant column”
])(
)(ln[
o
BS I
I
SeffS
Solar Io
Perform a Radiative Transfer Calculation to Account for Viewing Perform a Radiative Transfer Calculation to Account for Viewing Geometry and ScatteringGeometry and Scattering
Remove Scenes with IRemove Scenes with IB,c B,c > I> IB,oB,o
RcRo
IB,o IB,c
Pc
Rs
•LIDORT Radiative Transfer Model [Spurr et al., 2002]
•GOME Clouds Fields [Kurosu et al., 1999]
•GOME Surface Reflectivity [Koelemeijer et al., 2001]
HCHO Columns Retrieved from GOME (July 1996) HCHO Columns Retrieved from GOME (July 1996)
High HCHO regions reflect VOC emissions from fires, biosphere, human activity
-0.5
0
0.5
1
1.5
2
2.5x1016
moleculescm-2
SouthAtlanticAnomaly(disregard)
detectionlimit
Martin et al., 2002b
Tropospheric NOTropospheric NO22 Columns Retrieved from GOME Columns Retrieved from GOME
(July 1996) (July 1996)
6x1015
moleculescm-2
2
0
4
detectionlimit
GOME Observations Generally Consistent With GOME Observations Generally Consistent With In Situ Measurements from AircraftIn Situ Measurements from Aircraft
Latitude (degrees)
Houston Area Houston Area
Tennessee
Latitude (degrees)
In Situ NO2 Measurements by Tom Ryerson
In Situ HCHO Measurements by Alan Fried
GOME Observations Show NOGOME Observations Show NOxx-Limited Conditions Over -Limited Conditions Over
Most Polluted Regions During AugustMost Polluted Regions During AugustMajor Industrial Areas are Clear ExceptionsMajor Industrial Areas are Clear Exceptions
August
White areas indicate clouds or data below the GOME detection limit
Dependence of Ozone Production on NODependence of Ozone Production on NOxx and VOCs and VOCs
HOx family = OH + HO2 + RO + RO2
OH
RO2 RO
HO2
HNO3 H2O2O3
O3
O3
PHOx
1
2
34
56
“NOx- saturated” or“VOC-limited” regime
“NOx-limited” regime
VOC
NO
O2
NO
NO2
HCHO
]][[
][2)(
26
13 MNOk
VOCPkOP xHO ][2)(
5.0
543 NOk
PkOP HOx
Little sunlight or high NOx
Lots of sunlight or little NOx
Seasonal Seasonal Evolution from Evolution from NOx-Limited to NOx-Limited to NOx-Saturated NOx-Saturated
Conditions in FallConditions in Fall
GOME Observations Provide Confidence in a Recent Model PredictionGOME Observations Provide Confidence in a Recent Model Prediction NOx-Limited in the South and NOx-Saturated in the North in FallNOx-Limited in the South and NOx-Saturated in the North in Fall
Luo et al., JGR, 2000
GOME Model
Seasonal Maximum in Surface Ozone in Urban China Seasonal Maximum in Surface Ozone in Urban China Occurs in Fall (More High-Pressure Systems)Occurs in Fall (More High-Pressure Systems)
In-situ Surface Ozone Measurements
Luo et al., JGR, 2000
Fall NOx-saturated conditions noteworthy
Biomass Burning Emissions are Clearly NOBiomass Burning Emissions are Clearly NOxx-Limited, In -Limited, In
Contrast with NOContrast with NOxx-Saturated Conditions Over the -Saturated Conditions Over the
Industrial Highveld Industrial Highveld
August
Also observe plume evolution
Platform multiple ERS-2 Terra ENVISAT Aura CloudSat TBD
Sensor TOMS AVHRR/SeaWIFS
GOME MOPITT MODIS/MISR
SCIAMACHY
MIPAS TES OMI MLS CALIPSO OCO
Launch 1979 1995 1999 1999 2002 2002 2004 2004 2004 2004 2007
O3 N N/L L N/L N L
CO N N/L L N/L
CO2 N/L N
NO L
NO2 N N/L N
HNO3 L L
CH4 N/L N
HCHO N N/L N
SO2 N N/L N
BrO N N/L N
HCN L
aerosol N N N N N N
Present and Future Satellite Observations of Present and Future Satellite Observations of Tropospheric CompositionTropospheric Composition
Increasing spatial resolution
ConclusionsConclusions
Satellite remote-sensing of tropospheric NO2 and HCHO enables global characterization of ozone-NOx-VOC sensitivity
Most of the world is NOx-limited, especially during summer
NOx-saturated (VOC-limited) conditions occur under decreased sunlight or in major industrial centers
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