Modeling Studies of Air Quality in the Four Corners Region

National Park ServiceU.S. Department of the Interior

Cooperative Institute for Research in the Atmosphere

Marco Rodriguez1, Michael Barna2, Tom Moore3

1 CIRA, Colorado State University, Fort Collins, CO 2 National Park Service, Fort Collins, CO3 Western Regional Air Partnership, Western Governors’ Association, Fort Collins, CO

Workshop on Regional Emissions and Air Quality Modeling StudiesJuly 2008

Motivation• Ozone in the Western U.S is becoming an

increasing problem in remote areas

• Many Class I areas will be confronted with ozone concentrations that are trending towards the EPA's acceptable limits

• The growing development of oil and gas extraction operations throughout the West is essential to understand the potentially negative impact on air quality in some of the nation's protected areas

Methodology

• CAMx simulations at NPS-CIRA

2002 annual simulations (36 km)

• Emissions, meteorology from WRAP-RMC

• Model performance Evaluation

• Evaluate oil & gas impacts

Methodology• Significant increases in NOx and VOC for oil

and gas development in WRAP region

– largest emission increases in NM, CO, UT, WY

• To evaluate contribution to regional air pollution (e.g., ozone and fine nitrate PM) from O&G, consider two CAMx simulations

– base emissions

– base emissions minus O&G

• run SMOKE’s MRGGRID to combine all base02 emission categories except O&G

Methodology• The difference between these two runs

represents the impact of O&G emissions

• Results reflect an ‘emissions sensitivity test’, not a true source apportionment (CAMx’s OSAT better suited for that analysis)

NOx

VOC

Oil and gas emissions within WRAP:NOx: 125,000 tons/yr (3% of total)VOC: 363,000 tons/yr (2% of total)

Emissions from oil and gas in WRAP region

Parameter Choice36 km domain No nesting

Vertical Layers 19 sigma vertical layers (surface up to ~ 14 km).

Initial Conditions 15 days spin up time

Boundary Conditions Dirichlet set by GEOS-Chem GCM

Chemical Mechanism Carbon Bond IV

CAMx Simulation

Model Performance Evaluation

• Evaluation relies on Mean Fractional Bias (MFB) and Mean Fractional Error (MFE) estimates

• MFB and MFE “Bugle Plots”• MFB and MFE Spatial distributions

N

i ii

ii

OP

OP

NMFB

1

2

N

i ii

ii

OP

OP

NMFE

1

2

Ozone error and bias for all WRAPWRAP Ozone Fractional Error

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Bia

s

WRAP Ozone Fractional Bias

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Bia

s

fractional error

fractional bias

Ozone performance stats for all WRAP

EPA goal All sites(Western U.S)

Mean Observation 47

Mean Estimation 44

Standard deviation Obs. 13

Standard deviation Est. 12

Mean Bias Error -3

Mean Normalized Bias Error (%)

< ±15% -1.6

Mean Absolute Gross Error

10

Mean Absolute Normalized Gross Error (%)

< 35% 22.7

Mean Fractional Error (%) 23

Mean Fractional Bias (%) -5.8

WRAP NO3 Fractional Error

0

20

40

60

80

100

120

140

160

180

200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Err

or

(%)

IMPROVE

CASTNET

WRAP NO3 Fractional Bias

-200

-150

-100

-50

0

50

100

150

200

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Bia

s (%

)

IMPROVE

CASTNET

NO3 error and bias for all WRAPfractional error

fractional bias

WRAP Particulate NO3 Fractional Error

0

50

100

150

200

250

0 1 2 3 4 5

Average Concentration (ug/m3)

Fra

ctio

nal

Err

or

(%)

Goal

Criteria

IMPROVE

CASTNET

WRAP Particulate NO3 Fractional Bias

-200

-150

-100

-50

0

50

100

150

200

0 1 2 3 4 5

Average Concentration (ug/m3)

Fra

cti

on

al

Bia

s (

%)

Goal (+)

Goal (-)

Criteria (+)

Criteria(-)

IMPROVE

CASTNET

Annual Spatial Distribution

SO4 Fractional Bias SO4 Fractional Error

Annual Spatial Distribution

NO3 Fractional Bias NO3 Fractional Error

Annual Spatial Distribution

NH4 Fractional Bias NH4 Fractional Error

Example summertime ozone6 August 2002

Mesa Verde NP:65 ppb max hourlyconcentration

MEVE Ozone Fractional Bias

-0.2

-0.15

-0.1

-0.05

0

0.05

0.1

0.15

0.2

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Bia

s

MEVE Ozone Fractional Error

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Fra

ctio

nal

Bia

s

Ozone at Mesa Verde

fractional error fractional bias

Example ozone increase from O&G emissions, 6 August 2002

Ozone enhancements at Mesa Verde from O&G

July – August 2002

August 6

Ozone max. 8hr average in 2002

Concentrations Base case Concentrations O&G impacts

Ozone max. 8hr average O&G impacts

Concentrations O&G impacts Concentrations Base case

Ozone enhancements - Time SeriesBase Case O&G

enhancement

Summary• Acceptable ozone performance in WRAP

– 47 ppb (observed) vs. 44 ppb (predicted)

– fractional error: 0.23, fractional bias -0.06

– biases

• overpredict: fall through spring

• underpredict: summer

• low concentrations are overestimated

Summary (cont’d)• Nitrate performance not as good, but falls

within bugle plot limits

– wintertime overpredictions, summertime underpredictions

• Largest impacts from O&G emissions on regional ozone occur in Four Corners

– at Mesa Verde NP on 6 August 2002

• 8 ppb ozone enhancement

• peak ozone concentrations of 65 ppb

Summary (cont’d)

Limitations of this work:

– O&G emissions inventory has undergone several updates from the one used here

– No effects in CO because O&G emissions in phase I were accounted in the area emissions not O&G emissions

– Study does not provide information about the contributing sources (need for OSAT simulations)

AcknowledgmentsWestern Regional Air Partnership

– Tom Moore– Mohammad Omary

UNC-Chapel Hill, Carolina Environmental Program– Zac Adelman

ENVIRON International Corporation– Ralph Morris– Chris Emery