Working together for clean airWorking together for clean air

Puget Sound Area Ozone Modeling

NW AIRQUESTDecember 4, 2006

Puget Sound Area Ozone Modeling

NW AIRQUESTDecember 4, 2006

Washington State University

Puget Sound Clean Air Agency

Washington Department of Ecology

Washington State University

Puget Sound Clean Air Agency

Washington Department of Ecology

Overview/DisclaimerOverview/Disclaimer

Presentation will NOT be an in-depth “technical” exploration of the models.

Presentation WILL show how a local agency tapped into local (NW AIRQUEST) modeling resources to help answer internal policy/planning questions.

Presentation will NOT be an in-depth “technical” exploration of the models.

Presentation WILL show how a local agency tapped into local (NW AIRQUEST) modeling resources to help answer internal policy/planning questions.

Background – Ozone Levels in the Puget Sound AreaBackground – Ozone Levels in the Puget Sound Area

Background – Stakeholder charge & Future FactorsBackground – Stakeholder charge & Future Factors

“Although the modeling results demonstrated minimal reductions in ozone concentration as a result of implementing the strategies … … the air quality benefits produced by the strategies could be an important contribution to remaining in attainment.”

“…prudence requires that early identification of any potential impediments to remaining in attainment be vigorously pursued…”

“Although the modeling results demonstrated minimal reductions in ozone concentration as a result of implementing the strategies … … the air quality benefits produced by the strategies could be an important contribution to remaining in attainment.”

“…prudence requires that early identification of any potential impediments to remaining in attainment be vigorously pursued…”

Previous WSU modeling, based on a 1996 ozone event, contributed to stakeholder process and adopted strategies

Low Reid Vapor Pressure (RVP) gasoline

Stage II vapor recovery

Future Factors Moderate population and VMT growth Dramatic growth projected for local ports

Previous WSU modeling, based on a 1996 ozone event, contributed to stakeholder process and adopted strategies

Low Reid Vapor Pressure (RVP) gasoline

Stage II vapor recovery

Future Factors Moderate population and VMT growth Dramatic growth projected for local ports

Objectives and ImprovementsObjectives and Improvements

OBJECTIVES

To determine if the Puget Sound area is likely to remain in attainment in the future, using more updated inventory and methods.

To better understand the impact that low RVP gasoline has on ozone formation in the Puget Sound area.

To better understand ozone formation through sensitivity analyses.

OBJECTIVES

To determine if the Puget Sound area is likely to remain in attainment in the future, using more updated inventory and methods.

To better understand the impact that low RVP gasoline has on ozone formation in the Puget Sound area.

To better understand ozone formation through sensitivity analyses.

IMPROVEMENTS/CHANGES

CMAQ dispersion model (CALGRID used in previous)

MOBILE6 mobile model (MOBILE 5B used in previous)

Land surface model MM5 (simple soil MM5 in previous)

1998 ozone event (1998 concentrations higher than 1996)

1999 emission estimates (1996 NEI)

IMPROVEMENTS/CHANGES

CMAQ dispersion model (CALGRID used in previous)

MOBILE6 mobile model (MOBILE 5B used in previous)

Land surface model MM5 (simple soil MM5 in previous)

1998 ozone event (1998 concentrations higher than 1996)

1999 emission estimates (1996 NEI)

Modeling Project – Process and DesignModeling Project – Process and Design

Emissions Inventory Technical Group PSCAA, Ecology, WSU Inventory based largely on EPA’s 1999 National Emissions

Inventory Exception is non-road mobile (marine)

Base Case Year (1998)

Future Case Year (2015) Two scenarios run, with and without low Reid Vapor Pressure (RVP)

agreements

Sensitivity Runs Runs increasing and decreasing VOC and NOX in different combinations

Emissions Inventory Technical Group PSCAA, Ecology, WSU Inventory based largely on EPA’s 1999 National Emissions

Inventory Exception is non-road mobile (marine)

Base Case Year (1998)

Future Case Year (2015) Two scenarios run, with and without low Reid Vapor Pressure (RVP)

agreements

Sensitivity Runs Runs increasing and decreasing VOC and NOX in different combinations

Emissions Inventory SummaryVOC, NOX emissions reduce 20, 25% Emissions Inventory SummaryVOC, NOX emissions reduce 20, 25%

Emissions Inventory Comparison - 1998 and 2015 Scenarios

0

50

100

150

200

250

300

350

400

450

Area Point Nonroad Onroad Biogenic

Av

era

ge

To

ns

/Da

y

VOC 1998

VOC 2015 Low RVP

VOC 2015 High RVP

NOX 1998

NOX 2015

Inventory for PSCAA Counties - King, Kitsap, Pierce, Snohomish

Results – High Ozone SitesResults – High Ozone Sites

2015 ozone levels lower than 1998 at highest ozone sites High or low RVP gasoline made small difference in 2015 levels, less than 0.3 ppb at a monitor Poor model performance on second and third day of event

2015 ozone levels lower than 1998 at highest ozone sites High or low RVP gasoline made small difference in 2015 levels, less than 0.3 ppb at a monitor Poor model performance on second and third day of event

1-hour ozone at Enumclaw. Red = 1998 observations, blue = 1998 model, green = 2015 model (low RVP)

Results – “Urban Core” SitesResults – “Urban Core” Sites

Beacon Hill, near urban core, showed higher concentrations, in 2015 than 1998 Higher concentrations moving closer to urban area

Ozone/NOX ratios increasing from 1998 to 2015, smaller band “VOC-limited”

Not important for attainment status, but may potentially have public health implication

Beacon Hill, near urban core, showed higher concentrations, in 2015 than 1998 Higher concentrations moving closer to urban area

Ozone/NOX ratios increasing from 1998 to 2015, smaller band “VOC-limited”

Not important for attainment status, but may potentially have public health implication

1-hour ozone at Beacon Hill. Red = 1998 observations, blue = 1998 model, green = 2015 model

Results – Low RVP AgreementResults – Low RVP Agreement

Difference between 2015 “high” and “low” RVP scenarios less than 1 ppb

At individual monitoring sites, the difference is less than 0.3 ppb

Results – Sensitivity Analyses (based on 1998)Results – Sensitivity Analyses (based on 1998)

Reducing VOC (with NOX

constant or increasing) yields most optimal ozone reductions

Reducing VOC (with NOX

constant or increasing) yields most optimal ozone reductions

UncertaintiesUncertainties

Uncertainties in emissions inventory and projections Uncertainties in meteorological and dispersion

modeling Under-prediction in second, third day of event

Future uncertainties Lower future ozone NAAQS? “Background” concentrations from developing

countries Climate change effect?

Uncertainties in emissions inventory and projections Uncertainties in meteorological and dispersion

modeling Under-prediction in second, third day of event

Future uncertainties Lower future ozone NAAQS? “Background” concentrations from developing

countries Climate change effect?

Results – Objectives Met?Results – Objectives Met?

Modeling confirms previous results. The Puget Sound area is likely to remain in attainment in future years (with the current standard).

Voluntary low RVP gasoline will make little difference as cleaner cars are incorporated into the fleet in future years.

The region is “VOC limited.” VOC emissions reductions contribute to lower ozone concentrations. (caveat – sensitivity runs based on 1998 scenario).

Modeling confirms previous results. The Puget Sound area is likely to remain in attainment in future years (with the current standard).

Voluntary low RVP gasoline will make little difference as cleaner cars are incorporated into the fleet in future years.

The region is “VOC limited.” VOC emissions reductions contribute to lower ozone concentrations. (caveat – sensitivity runs based on 1998 scenario).

Post-Model Discussions/Input…Post-Model Discussions/Input…

Results inform PSCAA Programs

Voluntary Low Reid Vapor Pressure (RVP) gasoline in summer months

Vapor recovery (Stage II)

Results inform PSCAA Programs

Voluntary Low Reid Vapor Pressure (RVP) gasoline in summer months

Vapor recovery (Stage II)

Continuous Improvement

Possible model “metrics” (in addition to EPA’s guidance)

Model improvements

Continuous Improvement

Possible model “metrics” (in addition to EPA’s guidance)

Model improvements

Acknowledgements and QuestionsAcknowledgements and Questions

Many thanks to all who contributed:

Washington State Department of Ecology

Washington State University

Region 10 Environmental Protection Agency

Puget Sound Regional Council

Puget Sound Clean Air Agency

Many thanks to all who contributed:

Washington State Department of Ecology

Washington State University

Region 10 Environmental Protection Agency

Puget Sound Regional Council

Puget Sound Clean Air Agency

Results – Pack ForestResults – Pack Forest

1-hour ozone at Pack Forest. Red = 1998 observations, blue = 1998 model, green = 2015 model (low RVP)

Results – Model PerformanceResults – Model Performance

Overall, CMAQ model performance statistics met EPA guidance 1-hour mean normalized bias and error of -3% and 21% (guidance is 15%,

35%) 8-hour normalized bias of 1% (matched cell) and 9% (5 x 5 cells)

Very good agreement at Pack Forest Under-prediction at Enumclaw sites

Likely due to meteorology and over-prediction of planetary boundary layer Negative bias around 15% When include surrounding cells, negative bias around 10%

Scatter diagram, quantile-quantile plot show good agreement between observed and predicted

MM5 modeling generally shows an index of agreement ~0.8 for wind speed, direction, temperature, and humidity.

Overall, CMAQ model performance statistics met EPA guidance 1-hour mean normalized bias and error of -3% and 21% (guidance is 15%,

35%) 8-hour normalized bias of 1% (matched cell) and 9% (5 x 5 cells)

Very good agreement at Pack Forest Under-prediction at Enumclaw sites

Likely due to meteorology and over-prediction of planetary boundary layer Negative bias around 15% When include surrounding cells, negative bias around 10%

Scatter diagram, quantile-quantile plot show good agreement between observed and predicted

MM5 modeling generally shows an index of agreement ~0.8 for wind speed, direction, temperature, and humidity.

Results – Test of Future AttainmentWeyerhauser Mill, Lake Sammamish, Pack ForestResults – Test of Future AttainmentWeyerhauser Mill, Lake Sammamish, Pack Forest

Designed to take model uncertainty account, using model in a relative sense. Very Conservative as it takes 5 years into account.

1) Calculate current design values (DVC) based on 4th high 8-hour concentrations

2) Calculate the relative reduction factor from modeling

RRF = average 2015 8 hour maxaverage 1998 8 hour max

3) Calculate future design value = DVC * RRF

SITE RRF Future Design Value

WM 0.90 68 ppbLS 0.97 58 ppbPF 0.94 68 ppb

Designed to take model uncertainty account, using model in a relative sense. Very Conservative as it takes 5 years into account.

1) Calculate current design values (DVC) based on 4th high 8-hour concentrations

2) Calculate the relative reduction factor from modeling

RRF = average 2015 8 hour maxaverage 1998 8 hour max

3) Calculate future design value = DVC * RRF

SITE RRF Future Design Value

WM 0.90 68 ppbLS 0.97 58 ppbPF 0.94 68 ppb

Results – Sensitivity AnalysesResults – Sensitivity Analyses

8-hr 26-Jul 27-Jul 28-Jul ppm ppm ppm Base 0.093 0.096 0.077 No area 0.088 0.088 0.071 No biogenic 0.075 0.075 0.053 No on-road 0.088 0.084 0.070 No on-road VOC 0.088 0.083 0.067 No on-road NOX 0.105 0.098 0.082 No non-road 0.084 0.086 0.074 No non-road VOC 0.080 0.085 0.070 No non-road NOX 0.103 0.098 0.082 No point 0.095 0.095 0.076 % change from 1998 base No area -5% -8% -8% No biogenic -19% -22% -31% No on-road -5% -13% -9% No on-road VOC -5% -14% -13% No on-road NOX 13% 2% 6% No non-road -10% -10% -4% No non-road VOC -14% -11% -9% No non-road NOX 11% 2% 6% No point 2% -1% -1%

8-Hour Ozone Standard Exceeded with Entire Source Categories Removed

Emissions Inventory SummaryTotal VOCs estimated to decrease ~ 20%Emissions Inventory SummaryTotal VOCs estimated to decrease ~ 20%

VOC Sources 1998

Area, 142, 15%

Point, 16, 2%

Nonroad, 147, 16%

Onroad, 223, 24%

Biogenic, 410, 43%

TOTAL 938 Tons/Day VOC Sources 2015 ("high RVP" scenario)

Area, 158, 21%

Point, 16, 2%

Nonroad, 83, 11%

Onroad, 81, 11%

Biogenic, 410, 55%

TOTAL 748 Tons/Day

Inventory for PSCAA Counties - King, Kitsap, Pierce, Snohomish

Total 950 tons/day

Total 750 tons/day

Emissions Inventory SummaryNOX Emissions Estimated to Decrease ~25%Emissions Inventory SummaryNOX Emissions Estimated to Decrease ~25%

NOX Sources 1998

Onroad, 290, 55%

Biogenic, 2, 0%Area, 14, 3%

Point, 24, 5%

Nonroad, 195, 37%

TOTAL 525 Tons/Day NOX Sources 2015

Nonroad, 266, 68%

Onroad, 93, 23%

Biogenic, 2, 0%Area, 13, 3%

Point, 24, 6%

TOTAL 398 Tons/Day

Inventory for PSCAA Counties - King, Kitsap, Pierce, Snohomish Total 400 Tons/Day