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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.
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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
Funding for related projects U.S. EPA American Chemistry Council Datasets Draft prerelease datasets provided by ARB Acknowledgments
Trace 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
Model 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.
Family 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
Fundamental Photochemistry Tropospheric gas phase chemistry is driven by the OH radical: • Radical Initiation • Radical Propagation • Radical Termination • NOx termination
PSS 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
Radical 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
Radical 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
Radical and NOx termination OH + NO2 HNO3 HO2 + HO2 H2O2 HO2 + RO2 ROOH RO2 + NO RNO3 RO3 + NO2 PAN N2O5 + H2O 2 HNO3
Model Evaluation • 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]
Data Needs for Local Diagnostics • 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 Termination NO2 & 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 Cumulative Diagnostics • Radical Initiation & Termination (approximate): (2 peroxides + NOz ) • OH Chain Length (approximate): Ox / (2 peroxides + NOz ) 2 peroxides/NOz • NOx Termination, P(NOz): HNO3, speciated RNO3, NO3-, PAN • P(O3), P(Ox): O3, & O3 +NO2 + NOz
Model 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.
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 Uncertainties In CMAQ vs CAMx Comparison
Peak Model Ozone on Aug 5 (3rd day) Difficult to analyze effects accumulated over 3 days, so...
Start Evaluation with spinup (1st day) Comparison of O3 at 15:00 PDT:
Comparison of O3 aloft before start of 2d day Errata: all units are ppbV
Cumulative Pg(Ox) 7:00-19:00 PDT
CO conc. at 9:00 PDT in LA: inversion breaks up 2 hours later in CAMx…is timing of emissions wrong?
% contribution of O1D to OH initiation, cumulative for Aug 3.
Total new radical initiation, Layer 1, cumulative for Aug 3.
Ox production efficiency per NOx, cumulative for Aug 5. (Note: regions of gray within red are areas in which P(NOz) is negative).
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% Indicators to Evaluate O3 Sensitivity
Indicator of O3 sensitivity: %HO2+NO (cumulative for Aug 5).
Indicator of O3 sensitivity: %OH+HC (cumulative for Aug 5). (Note colormap is inverted)