february 14, 2001, scos97-narsto dataworkshop
DESCRIPTION
Data Needs for Evaluation of Radical and NOy Budgets in SCOS97-NARSTO Air Quality Model Simulations. Gail S. Tonnesen University of California, Riverside Bourns College of Engineering Center for Environmental Research and Technology. February 14, 2001, SCOS97-NARSTO DataWorkshop. - PowerPoint PPT PresentationTRANSCRIPT
Center for Environmental Research and Technology/Environmental Modeling
University of California at Riverside
Data Needs for Evaluation of Radical and Data Needs for Evaluation of Radical and NOy Budgets in SCOS97-NARSTO Air NOy Budgets in SCOS97-NARSTO Air
Quality Model SimulationsQuality Model Simulations
February 14, 2001, SCOS97-NARSTO DataWorkshop
Gail S. Tonnesen
University of California, RiversideBourns College of Engineering
Center for Environmental Research and Technology
Center for Environmental Research and Technology/Environmental Modeling
University of California at Riverside
AcknowledgmentsAcknowledgments
• Funding for related projects– U.S. EPA– American Chemistry Council
• Datasets – Draft prerelease datasets provided by ARB
Center for Environmental Research and Technology/Environmental Modeling
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Trace Gas Governing EquationsTrace Gas Governing Equations
• j=1,N Coupled PDEs
Cj t v.Cj + D2Cj + P(C) L(C)Cj + Ej Dj
• Operator Splitting:
Cj t = v.Cj
Cj t = D2Cj + Ej Dj
dCj dt = P(C) L(C)Cj
Gear solver is the gold standard for stiff ODEs
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Model EvaluationModel Evaluation
• Verification, Validation or Evaluation?– Oreskes et al., 1994.
• Comparisons with ambient data.
• Validation of component processes.
• Indicators for testing O3 sensitivity.
• Sensitivity and uncertainty analysis.
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Family DefinitionsFamily Definitions
NOx = NO + NO2 + (NO3 + 2 N2O5 + HONO + HNO4)
NOz = HNO3 + RNO3 + NO3– + PAN
NOy = NOx + NOz = total oxidized nitrogen.
HC = VOC (or ROG) + CH4 + CO
Ox = O3 + O + NO2 + NOz + 2 NO3 + 3 N2O5 + HNO4
HOx = OH + HO2 + RO2
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Fundamental PhotochemistryFundamental Photochemistry
Tropospheric gas phase chemistry is driven by the OH radical:
• Radical Initiation
• Radical Propagation
• Radical Termination
• NOx termination
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PSS EquilibriumPSS Equilibrium
NO2 + h NO + O
O + O2 O3
O3 + NO O2 + NO2
NO2 + O3 NO3 + O2
NO3 + h NO2 + O
P(Ox): RO2 + NO RO + NO2
HO2 + NO OH + NO2
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Radical InitiationRadical Initiation
O3 + h O(1D)
O(1D) + H2O 2 OH
HCHO + h 2 HO2 + CO HO2 + NO OH + NO2
HONO + h OH + NO
PAN RO3 + NO2
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Radical PropagationRadical Propagation
OH + CH4 + O2 CH3 O2 + H2O
CH3O2 + NO NO2 + CH3O
CH3O + O2 HO2 + HCHO
HO2 + NO NO2 + OH
2x( NO2 + h + O2 O3 + NO )
Net Reaction:
CH4 + 4 O2 2 O3 + HCHO + H2O
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Radical and NORadical and NOxx termination termination
OH + NO2 HNO3
HO2 + HO2 H2O2
HO2 + RO2 ROOH
RO2 + NO RNO3
RO3 + NO2 PAN
N2O5 + H2O 2 HNO3
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Center for Environmental Research and Technology/Environmental Modeling
University of California at Riverside
Center for Environmental Research and Technology/Environmental Modeling
University of California at Riverside
Center for Environmental Research and Technology/Environmental Modeling
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• Local Diagnostics– Instantaneous reaction rates at a given site.
– Examples: P(OH), P(Ox), P(Ox)/P(NOz)
– Cannot get production rates from time-series!
• Cumulative Trajectory Diagnostics– cumulative history of reaction rates and other
loss processes in an air parcel integrated over hours or days.
– Examples: [H2O2], [HNO3], [O3], [O3]/[NOz]
Model EvaluationModel Evaluation
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• Radical Initiation J-values & HCHO, O3, H2O, HONO, H2O2, PAN
• OH Chain Length
kOH HCi /( kOH HCi + kOH NO2 )
kHO2 NO /(kHO2 NO + kHO2 (RO2+ 2 HO2 ) )
• Radical TerminationNO2 & OH, HO2 & RO2, NO & RO2, O3
• NOx Termination, P(NOz):NO2 & OH, NO & RO2, NO2 & RCO3, NO3, N2O5 & H2O
• Pg(Ox)
NO, HO2, RO2.
Data Needs for Local DiagnosticsData Needs for Local Diagnostics
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• Radical Initiation & Termination (approximate):Radical Initiation & Termination (approximate): (2 peroxides + NO(2 peroxides + NOz z ))
• OH Chain Length (approximate):OH Chain Length (approximate):OOx x / (2 peroxides + NO/ (2 peroxides + NOz z ))
2 peroxides/NO2 peroxides/NOz z
• NONOxx Termination, P(NO Termination, P(NOzz):):
HNOHNO33, speciated RNO, speciated RNO33, NO, NO33--,, PAN PAN
• P(OP(O33), P(O), P(Oxx):):
OO33, & O, & O33 +NO +NO22 + NO + NOzz
Data Needs for Cumulative DiagnosticsData Needs for Cumulative Diagnostics
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Model Domain and ParametersModel Domain and Parameters
• 1997 Southern California Ozone Study (SCOS97). Aug 3 to 5, 1997
• CMAQ and CAMx
• MM5 16 layers
• CB4 chemical mechanism
• Gear CMAQ, CMC CAMx
• Bott Advection Scheme
• No Aerosols
• Includes process analysis diagnostic outputs.
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Uncertainties In CMAQ vs CAMx Uncertainties In CMAQ vs CAMx ComparisonComparison
• Timing in CAMx - are emissions calculated as PST or PDT?
• Vertical mixing - CAMx has less vertical dispersion in early morning?
• Emissions - CMAQ may be missing large point sources.
• Problem with isoprene in CAMx
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Peak Model Ozone on Aug 5 (3rd day)
Difficult to analyze effects accumulated over 3 days, so...
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Start Evaluation with spinup (1st day) Comparison of O3 at 15:00 PDT:
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Comparison of O3 aloft before start of 2d day
Errata: all units are ppbV
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Pg(Ox) 7:00-8:00 PDT
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Pg(Ox) 8:00-9:00 PDT
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Pg(Ox) 9:00-10:00 PDT
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Pg(Ox) 10:00-11:00 PDT
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Pg(Ox) 11:00-12:00 PDT
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Cumulative Pg(Ox) 7:00-19:00 PDT
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CO conc. at 9:00 PDT in LA: inversion breaks up 2 hours later in CAMx…is timing of emissions wrong?
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Cumulative P(OH) 7:00-19:00 PDT, Aug 3.
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H2O at 12:00 PDT
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% contribution of O1D to OH initiation, cumulative for Aug 3.
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HO2 initiation, cumulative for Aug 3.
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RO2 radical initiation, cumulative for Aug 3.
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Reactions of NO3 & O3 with isoprene, cumulative for Aug 3.
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Reactions of OH with isoprene, cumulative for Aug 3.
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Total new radical initiation, Layer 1, cumulative for Aug 3.
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Total OH Production, Layer 1, cumulative for Aug 3.
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HNO3 mixing ratio, 24:00 PDT, Aug 5.
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HNO3 produced by OH+NO2, Layer 1, cumulative for Aug 5.
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HNO3 produced by OH+NO2, Later 3, cumulative for Aug 5.
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HNO3 produced by N2O5+H2O, cumulative for Aug 5.
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E-W Slice through LA, cumulative for Aug 5.
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Fraction HNO3 of total NOz, cumulative for Aug 5.
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Net Production of PAN, cumulative for Aug 5.
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Production of organic nitrates, cumulative for Aug 5.
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Total Production of NOz, cumulative for Aug 5.
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Ox production efficiency per NOx, cumulative for Aug 5. (Note: regions of gray within red are areas in which P(NOz) is negative).
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Indicators to Evaluate O3 SensitivityIndicators to Evaluate O3 Sensitivity
• Indicators based on HNO3 or NOz may fail in CAMx simulations due to large contribution of N2O5+H2O to P(HNO3).
• Alternative: Use indicators based on radical propagation efficiency, O3 is VOC sensitive for:
%HO2+NO > 93%
%OH+HC < 80%
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Indicator of O3 sensitivity: %HO2+NO (cumulative for Aug 5).
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Indicator of O3 sensitivity: %OH+HC (cumulative for Aug 5).(Note colormap is inverted)
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ConclusionsConclusions
• Minor problems with emissions, vertical dispersion and time zone need to be corrected before full evaluation.
• More serious issue w.r.t. N2O5 chemistry.
• Uncertainty in fate of NOx is a critical issue for
O3 sensitivity and weekend effects.
• Validation of HOx budgets is equally important.
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RecommendationsRecommendations
• Should adopt an up-to-date mechanism
– SAPRC99, CB4-99, RACM2.
• Use NOy data to better characterize N2O5
chemistry and NOx fate.
• Use sensitivity studies to evaluate effects of uncertainty in N2O5 chemistry.