Data Needs for Evaluation of Radical and NOy Budgets in SCOS97-NARSTO Air Quality Model Simulations
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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


Acknowledgments

Funding for related projects SCOS97-NARSTO Air Quality Model Simulations

U.S. EPA

American Chemistry Council

Datasets

Draft prerelease datasets provided by ARB

Acknowledgments


Trace Gas Governing Equations SCOS97-NARSTO Air Quality Model Simulations

  • j=1,N Coupled PDEs

    Cj t  v.Cj + D2Cj + P(C)  L(C)Cj + Ej  Dj

  • Operator Splitting:

    Cj t = v.Cj

    Cj t = D2Cj + Ej  Dj

    dCj dt = P(C)  L(C)Cj

    Gear solver is the gold standard for stiff ODEs


Model Evaluation SCOS97-NARSTO Air Quality Model Simulations

  • 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 SCOS97-NARSTO Air Quality Model Simulations

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 SCOS97-NARSTO Air Quality Model Simulations

Tropospheric gas phase chemistry is driven by the OH radical:

  • Radical Initiation

  • Radical Propagation

  • Radical Termination

  • NOx termination


PSS Equilibrium SCOS97-NARSTO Air Quality Model Simulations

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 SCOS97-NARSTO Air Quality Model Simulations

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 SCOS97-NARSTO Air Quality Model Simulations

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 NO SCOS97-NARSTO Air Quality Model Simulationsx termination

OH + NO2  HNO3

HO2 + HO2 H2O2

HO2 + RO2 ROOH

RO2 + NO RNO3

RO3 + NO2 PAN

N2O5 + H2O  2 HNO3


Model Evaluation SCOS97-NARSTO Air Quality Model Simulations

  • 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 SCOS97-NARSTO Air Quality Model Simulations

  • 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 SCOS97-NARSTO Air Quality Model Simulations

  • 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 SCOS97-NARSTO Air Quality Model Simulations

  • 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.


Uncertainties in cmaq vs camx comparison

Timing in CAMx - are emissions calculated as PST or PDT? SCOS97-NARSTO Air Quality Model Simulations

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) SCOS97-NARSTO Air Quality Model Simulations

Difficult to analyze effects accumulated over 3 days, so...


Start Evaluation with spinup (1st day) SCOS97-NARSTO Air Quality Model Simulations

Comparison of O3 at 15:00 PDT:


Comparison of O3 aloft before start of 2d day SCOS97-NARSTO Air Quality Model Simulations

Errata: all units are ppbV


Pg(Ox) 7:00-8:00 PDT SCOS97-NARSTO Air Quality Model Simulations


Pg(Ox) 8:00-9:00 PDT SCOS97-NARSTO Air Quality Model Simulations


Pg(Ox) 9:00-10:00 PDT SCOS97-NARSTO Air Quality Model Simulations


Pg(Ox) 10:00-11:00 PDT SCOS97-NARSTO Air Quality Model Simulations


Pg(Ox) 11:00-12:00 PDT SCOS97-NARSTO Air Quality Model Simulations


Cumulative Pg(Ox) SCOS97-NARSTO Air Quality Model Simulations

7:00-19:00 PDT


CO conc. at 9:00 PDT in LA: inversion breaks up 2 hours SCOS97-NARSTO Air Quality Model Simulations

later in CAMx…is timing of emissions wrong?


Cumulative P(OH) 7:00-19:00 PDT, Aug 3. SCOS97-NARSTO Air Quality Model Simulations


H2O at 12:00 PDT SCOS97-NARSTO Air Quality Model Simulations


















Ox production efficiency per NOx, cumulative for Aug 5. 3.

(Note: regions of gray within red are areas in which P(NOz) is negative).


Indicators to evaluate o3 sensitivity

Indicators based on HNO 3.3 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




Conclusions 5).

  • 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.


Recommendations 5).

  • 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.


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