Robin L. Dennis

Atmospheric Sciences Modeling DivisionAir Resources Laboratory, NOAA/US EPA

Research Triangle Park, NC 27711

European Monitoring and Evaluation Program (EMEP)Workshop on Particulate Matter Measurement and Modeling

April 20-23, 2004New Orleans, Louisiana, USA

Evaluation of 3-D RegionalParticulate Models:

Measurement Needs for Inorganic Species

Acknowledgements

Shawn Roselle and Shaocai Yu provided valuable assistance in making the CMAQ runs and conducting analyses.

Preliminary Supersite data were provided by Spyros Pandis (Pittsburgh) and Jay Turner (St. Louis). Data were provided

by the SEARCH and the Atlanta Supersite Programs.

Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency

policy.

Robin Dennis is on assignment to the National Exposure Research Laboratory, U.S. Environmental Protection Agency

Policy Issues for the Inorganic System*

• Are we getting the right mix of inorganic fine particles

• What degree of nitrate replacement for sulfate will there be

• Which is more effective: NOX control or NH3 control– What are other consequences (e.g., acidity, O3, SO4

2-, SOA)– What happens to character as well as mass

• What is degree of acidity of aerosols in general and sulfate

• What is the effectiveness of urban-oriented controls

• New insights from special measurement campaigns

* Courtesy of John Bachmann, EPA

PRIMARY EMISSIONS

VOC

CO NOSO2

NH3

NO2

HNO3 H2SO4

O3

Gas Phase

Fine Particles

hv

OH

O3

OH

OHHO2RO2

NO3

PMfine

SO4

PMfine

H2O2O3Fe

O3NO3

N2O5

H2OHeterogeneous

Evaluation Thrusts(Focus of the testing and the talk)

• System Setup• Budgets

• Gas/Particle Partitioning• Current state of the gas/aerosol system

• Response Dynamics• Move to future states of the gas/aerosol system

Log10 Annual Area Source Ammonia Emissions

Summer: August 1999 Winter: January 2002 CMAQ @ 32-km resolution CMAQ @ 36-km resolution

3 Sites:

Pittsburgh, PA

St. Louis, MO

Atlanta, GA

System Setup(budgets)

• SOX emissions• Sulfate production and losses• NOX emissions

• Total-Nitrate (HNO3+aNO3-) production and losses

• Day (gas) versus nighttime (heterogeneous) pathway differences

• NHX (NH3+NH4+) emissions and losses

• Getting NHX right is important (dilemma: official or best for model?)» Seasonal» Daily» Diurnal

• Meteorological inputs• Boundary layer height (sensible/latent heat); vertical mixing rates

Jefferson Street Jan02 (9 Day) CMAQ Comparisons

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

0 4 8 12 16 20 24

Hour (EST)

HNO

3 Av

erag

e (p

pb)

02Release NewHeteroRxn NoHeteroRxn JSTHNO3

Yorkville Jan02 (9 Day) CMAQ Comparisons

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0 4 8 12 16 20 24

Hour (EST)

HNO

3 Av

erag

e (p

pb)

02Release NewHeteroRxn NoHeteroRxn YRKHNO3

•HNO3 concentrations significantly reduced with updated CMAQ•Must turn off all production from N2O5 to get down to observed levels of HNO3•Daytime over-production of HNO3 is also an issue (winter photochemistry)•These are more winter than summer issues

Atlanta: HNO3 (average diurnal cycle)

Urban Suburban

•Inverse modeling against monthly NH4 wet concentrations was used to define seasonality of NH3 emissions

•Having the correct NH3 seasonality was critical to getting surface NHx right

Jefferson St Aug99 NHx Comparison

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

8/13 8/16 8/19 8/22 8/25 8/28 8/31

Day (EST, 8/13-8/31 1999)

Tota

l NHX

(ug/

m3 )

JeffStNHx 02Model 03ModelNHx

The CMAQ NHX predictions track the synoptic signal quitewell, but they do not track the measured diurnal pattern

Atlanta: NHX

Jefferson Street Aug99 ANO3 Diurnal Average Comparison

0

1

2

3

4

5

6

7

8

9

0 4 8 12 16 20 24

Hour (EST)ANO3 (u

g/m

3)

JSTANO3 02ModelANO3 H3uModelNO3

Diurnal biases in NHX show up as biases in aerosol nitrate,especially in the early morning.

Atlanta: NO3-

Jefferson St Aug99 Diurnal Ave NHx Comparison

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7.0

8.0

9.0

0 4 8 12 16 20 24

Hour (EST) [Period = 8/15-8/31]

Tota

l NH

X (u

g/m

3)

JST-StNHx 02Mod-StNHx 03Mod-StNHx

Atlanta: NHX

Aug99 (Month) CMAQ Jefferson St Compare

0102030405060708090

100

0 4 8 12 16 20 24

Hour (EST)

NOy

(ppb

)

JSTNOy 02ModelNOy 03Mod4.3NOy

Aug99 (Month) CMAQ Centerville Compare

0123456789

0 4 8 12 16 20 24

Hour (EST)

NO

y (p

pb)

CTRNOy

ModelNOy

Rural NOY

Urban NOY

We see a pattern of early evening overprediction at urban and rural Sites. We believe the PBL is collapsing pre-maturely.

Measurements to Support EvaluationSystem Setup

• Inert/slowly reacting “primary” specie (check meteorology) EC will do; also NOY and CO

• Temperature (soil moisture)• SO4

2-

• NOY, HNO3 (O3, NOX [= NO + true-NO2] to examine O3 production)• Total-Nitrate (total because looking at budgets)• NHX (total because looking at budgets)• Wet deposition, rainfall amounts (dry deposition)

Gas/Particle Partitioning(Current conditions)

• Equilibrium dynamics• Model errors affecting the partitioning

» Temperature• Measurement errors affecting the testing of equilibrium module

• Other conditions than assumed in the model• Non-equilibrium dynamics• External instead of internal mixture• Non-equilibrium pathways

• Coarse particle interactions• Loss pathways

-2

0

2

4

6

8

10

-10 -5 0 5 10 15 20 25

Data 5TemperatureRobinNO3 (observed Temperature)NO3 (MM5 Temperature)

NO

3- (

g m

-3)

Observed Temperature

Fig. Difference in predictions of aerosol NO3

- with observed and modeled (MM5) temperatures at the Pittsburgh site

0

2

4

6

8

10

0 2 4 6 8 10

NO

3- (MM

5 T)

NO3

- (observed T)

-10

-5

0

5

10

15

20

25

-10 -5 0 5 10 15 20 25

MM

5 T

(C)

observed T (C)Time (EST, 2002)

-10-505

10152025

1/2 1/6 1/10 1/14 1/18 1/22 1/26 1/30

Observed TemperatureMM5 Temperature

Tem

pera

ture

(C)

0

2

4

6

8

10

1/2 1/6 1/10 1/14 1/18 1/22 1/26 1/30

NO3 (observed Temperature)NO3 (MM5 Temperature)

NO

3- (

g m

-3)

Differences in predictions of NO3- with observed and modeled (MM5)

temperatures at the Pittsburgh site in January 2002. Differences aregreatest at the higher temperatures.

Base-case aerosol NO3

- ( g m-3)

Sen

sivi

tity-

case

aer

osol

NO

3- ( g

m-3

)

10-3

10-2

10-1

100

101

Errors in SO4

2- and TNH4

10-3

10-2

10-1

100

101

Errors in SO4

2-

10-3

10-2

10-1

100

101

10-3 10-2 10-1 100 101

Errors in TNH4

Base-case aerosol NO3

- ( g m-3)

Sen

sivi

tity-

case

aer

osol

NO

3- ( g

m-3

)

10-3

10-2

10-1

100

101

Errors in SO4

2- and TNH4

10-3

10-2

10-1

100

101

Errors in SO4

2-

10-3

10-2

10-1

100

101

10-3 10-2 10-1 100 101

Errors in TNH4

Base-case aerosol NO3

- ( g m-3)

Sen

sivi

tity-

case

aer

osol

NO

3- ( g

m-3

)

10-3

10-2

10-1

100

101

Errors in SO4

2- and TNH4

10-3

10-2

10-1

100

101

Errors in SO4

2-

10-3

10-2

10-1

100

101

10-3 10-2 10-1 100 101

Errors in TNH4

Ran

dom

err

or s

ensi

tivity

aer

osol

NO

3- (ug

/m3 )

Base case aerosol NO3- (ug/m3)

•Gaussian random error (1σ=15% to mimic measurement error) superimposedon inputs of SO4

2- and NHX causes a large uncertainty in the prediction of NO3-.

•The error in NHX has a larger impact than the error in SO42-.

7/25 7/260

2

4

6

8

Aer

osol

Nitr

ate

(g

/m3 )

DateDate

Aer

osol

Nitr

ate

(g

/m3 )

observed range median of predicted

1/20 1/21 1/2202468

10

1/15 1/16 1/170

2

4

6

8

observed range median of predicted

Figure 3. Results from Monte Carlo simulations performed for selected periods in July 2001 and January 2002. Error bars extend to the 5th and 95th percentiles of the cumulative distribution function associated with each prediction. The shaded area bounds the interval between the 5th and 95th percentiles of the observed aerosol nitrate cumulative distribution functions, although concentrations below zero are not shown. (courtesy Spyros Pandis)

11 14 17 200

1

2

3

11 14 17 20

observed predicted

July 9 July 21

internally mixed liquid

11 14 17 200

1

2

3

Aer

osol

Nitr

ate

(g/

m3 )

Hour11 14 17 20

externally mixed liquid + solid

Figure 5. Simulations for July 9 and 21 assuming that particles are 1) internally mixed liquid aerosols, and 2) an external mixture of crystallized ammonium sulfate and wet acidic

aerosols when the relative humidity is below 40%. (courtesy Spyros Pandis)

Jefferson Street Aug99 ANO3 Diurnal Average Comparison

0

1

2

3

4

5

6

7

8

9

0 4 8 12 16 20 24

Hour (EST)

AN

O3

(ug/

m3)

JSTANO3 02ModelANO3 H3uModelNO3

August ’99 Atlanta: NO3-

While there appears to be a daytime under-prediction of NO3- by the model,

single-particle mass spec measurements (Lee, Murphy, et al.) show the nitratewas not associated with ammonium (i.e., not the standard equilibrium pathway).

Measurements to Support EvaluationGas/Particle Partitioning

• SO42-

• HNO3 and NO3-

• NH3 and NH4+

• Base cations (coarse and fine)• Single particle mass spectrometer particle composition

information• Coarse particles (chemical composition by size)• T, RH• Good characterization of measurement error; best

accuracy and precision possible (10%)

Response Dynamics

• Gas Ratio (Excess Ammonia), modified Gas Ratio• Hourly• Daily

• Degree of neutralization

• Gas/Particle fractions

Gas Ratio(per S. Pandis)

Free Ammonia NHX - 2 * SO42-

GR = ---------------------- = ------------------------------

Total Nitrate HNO3(g) + NO3-(p)

Calculated in Molar Units

GR > 1 => HNO3 limiting

0 < GR < 1 => NH3 limiting

GR < 0 => NH3 severely limiting (can’t form NH4NO3)

Gas Ratio for Pittsburgh: Winter 2002

-8.0

-6.0

-4.0

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1/4/

2002

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1/7/

2002

0:0

0

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/200

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00

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/200

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00

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/200

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00

1/19

/200

2 0:

00

1/22

/200

2 0:

00

1/25

/200

2 0:

00

1/28

/200

2 0:

00

1/31

/200

2 0:

00

Day : Start-Hour

Gas

Rat

io

SchPk Gas Ratio H3uModGasRatio

The modeled and observed Gas Ratios are reasonably consistent. The majorexcursions are mostly associated with plume(1) and wet deposition events(3).

Gas Ratio for Pittsburgh: Winter 2002

-8.0

-6.0

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1/4/

2002

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1/7/

2002

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1/10

/200

2 0:

00

1/13

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2 0:

00

1/16

/200

2 0:

00

1/19

/200

2 0:

00

1/22

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2 0:

00

1/25

/200

2 0:

00

1/28

/200

2 0:

00

1/31

/200

2 0:

00Day : Start-Hour

Gas

Rat

io

SchPk Gas Ratio H3uModGasRatio

Daily Gas Ratio Compare: Pittsburgh Winter 2002

-4.0

-3.0

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1/2/20

02

1/6/20

02

1/10

/200

2

1/14

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1/18

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2

1/22

/200

2

1/26

/200

2

1/30

/200

2

Day : Start-Hour

Gas

Ratio

SchPark-SS Gas Ratio 03Release

A fair amount of the hourly Gas Ratio comparison information is able to becaptured by daily Gas Ratio comparisons, although interpretation is mostinsightful and reliable at the hourly time resolution.

St Louis Jan 2002 CMAQ Gas Ratio Comparison

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12/31/2001 1/5/2002 1/10/2002 1/15/2002 1/20/2002 1/25/2002 1/30/2002

Day

Dai

ly G

as R

atio

H3uModel Gas Ratio NoN2O5Model Gas Ratio StL-SSObs Gas Ratio

Daily Gas Ratio Compare: Pittsburgh Winter 2002

-4.0

-3.0

-2.0

-1.0

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1.0

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4.0

1/2/20

02

1/6/20

02

1/10

/200

2

1/14

/200

2

1/18

/200

2

1/22

/200

2

1/26

/200

2

1/30

/200

2

Day : Start-Hour

Gas

Ratio

SchPark-SS Gas Ratio 03Release

Gas Ratio comparisons can vary considerable across space due to differencesin model biases. At Pittsburgh Total-Nitrate and NHX are both biased high. AtSt. Louis Total-Nitrate is high and NHX is biased low.

• SO42-

• Minimally Total-Nitrate, but prefer HNO3 and NO3-

• Minimally NHX, but prefer NH3 and NH4+

• Temperature (for interpretation)• Precipitation (for interpretation)• Wet deposition (for interpretation)

Measurements to Support EvaluationResponse Dynamics

Summary of Evaluation Measurement Needs• Critical Suite (continuous)

• SO2 and SO42-

• HNO3 and NO3- (Total-Nitrate as 2nd choice)

• NH3 and NH4+ (NHX as 2nd choice)

• Base cations (coarse and fine) and other anions (e.g., Cl and Br)• Inert/slowly reacting “primary” specie (check meteorology)

» EC will do; also NOY and CO• T, RH, Precipitation, WD• Wet deposition (Daily; Weekly as 2nd choice)

• Additions for a Full Set (continuous)• NOY, HNO3, O3, NOX (=NO+true-NO2), H2O2, PAN (Ox. capacity; O3 prod’n)• Coarse particles (chemical composition by size)• Single particle mass spectrometer particle composition data• Good characterization of measurement error; best accuracy and

precision possible (goal: 10%)• Dry deposition flux (direct as possible) of gases and particles• Satellite sites for sub-grid variability studies

• Hourly vs. Daily perspective (need continuous)• Now: Several continuous, Many/most daily sites with critical suite• Future: Most sites with critical suite of continuous measurements

• Summer vs. Winter perspective• Winter needs to get equal experiment time for special intensives

» Eventually the entire year needs to be covered

• Regional/Rural vs. Local/Urban• Harmonize techniques. If separate networks, then need to have careful

intercomparisons» Degree of comparability needs to be established

• Wet and Dry Deposition perspective• Wet: collocation; daily most useful but pragmatism may say longer• Dry: issue of carrying out special measurement programs - particles

• Subgrid Variability• Attacked through select measurement clusters (annual)

» Variability of budgets (setup), species partitioning, Gas Ratio

Summary of Eval. Measurement Needs (cont.)

Extra Slides

PRIMARY EMISSIONS

VOC

CO NOSO2

NH3

NO2

HNO3 H2SO4

O3

Gas PhaseFine Particles

hv

OH

O3

OH

OHHO2RO2

NO3

PMfine

SO4

PMfine

H2O2O3Fe

NO3

PMcoarse

SO4

PMcoarse

Coarse Particles

O3NO3

N2O5

H2OHeterogeneous

Yorkville Jan02 (9 Day) CMAQ Comparisons

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 4 8 12 16 20 24

Hour (EST)

HNO

3 Av

erag

e (p

pb)

NewHeteroRxn NewHet-CB4 NoHeteroRxn YRKHNO3

Suburban Atlanta: HNO3(average diurnal cycle)

•Daytime over-production of HNO3 is also an issue

Schenley Park Jan02 (3.5 Week) CMAQ Comparisons

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

0 4 8 12 16 20 24

Hour (EST)

gasH

NO3

Aver

age

(ug/

m3)

02Release NewHeteroRxn NoHeteroRxn SCHPKHNO3

•Same behavior of HNO3 overprediction is observed at Pittsburgh.•The overprediction of HNO3 appears relatively smaller in summer (no daytime issue) than in winter. Winter may have bigger issues.

Pittsburgh: Winter Atlanta: Summer

Jefferson Street Aug99 HNO3 Diurnal Average Comparison

0123456

789

10

0 4 8 12 16 20 24

Hour (EST)

HNO

3 (p

pb)

JSTHNO3 02ModelHNO3 H3uModelHNO3

Fig. Difference in predictions of aerosol NO3

- with observed and modeled (MM5) temperatures at the Pittsburgh site

0

2

4

6

8

10

0 2 4 6 8 10

NO

3- (M

M5

T)

NO3

- (observed T)

-10

-5

0

5

10

15

20

25

-10 -5 0 5 10 15 20 25

MM

5 T

(C)

observed T (C)Time (EST, 2002)

-10-505

10152025

1/2 1/6 1/10 1/14 1/18 1/22 1/26 1/30

Observed TemperatureMM5 Temperature

Tem

pera

ture

(C)

0

2

4

6

8

10

1/2 1/6 1/10 1/14 1/18 1/22 1/26 1/30

NO3 (observed Temperature)NO3 (MM5 Temperature)

NO

3- (

g m

-3)

Comparison of Gas Ratio Frequency for Pittsburgh January 2002 (1/5/02 - 1/29/02)

020406080

100120140160180

<0 0.5 1.0 1.5 2.0 3.0 >3

Bin Range

2-H

ourly

Bin

Cou

nt

Schenley ParkH3uModGasRatioZeroModGasRatio02ModGasRatio

PittsburghFull Period

The CMAQ O3 Release is best even though it has biases. CMAQ with Zero N2O5 is not as good even though its total-Nitrate looks best.

Comparison of Gas Ratio Frequency for St LouisJanuary 4 - 30, 2002

0

2

4

6

8

10

12

14

0.5 1 1.5 2 3 4 >4

Gas Ratio Bin Range

Dai

ly A

vera

ge B

in C

ount

Stl-SSObsH3uMod03RelZeroN2O5Mod

The CMAQ O3 Release is worst (02 CMAQ Release would be much worse). CMAQ with Zero N2O5 is closest to Observations

St Louis