Transboundary influences on us background ozone
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Transboundary influences on US background ozone. Huiqun Wang 1 ([email protected]) Philippe Le Sager 2 ([email protected]) Rokjin Park 3 ([email protected]) Daniel Jacob 2 ([email protected]). Smithsonian Astrophysical Observatory Harvard University

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Transboundary influences on US background ozone

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Transboundary influences on us background ozone

Transboundary influences on US background ozone

Huiqun Wang1 ([email protected])

Philippe Le Sager2 ([email protected])

Rokjin Park3 ([email protected])

Daniel Jacob2 ([email protected])

  • Smithsonian Astrophysical Observatory

  • Harvard University

  • Seoul National University

Work sponsored by U.S. Department of Energy, Office of Fossil Energy, through a contract with Argonne National Laboratory


Transboundary influences on us background ozone

According to EPA, counties violating the current 80 ppb ozone standard are largely limited to southern California, the Northeast coastal corridor, and isolated other parts of the eastern US


Transboundary influences on us background ozone

EPA further shows that lowering the standard to 75 ppb or 70 ppb would significantly increase the number of counties in violation,

based on current air quality data


Application of geos chem global air quality model to quantify transboundary pollution influence

Application of GEOS-Chem global air quality modelto quantify transboundary pollution influence

  • GEOS-Chem is a global model of ozone-PM chemistry using here NASA/GEOS assimilated meteorological data for 2001; horizontal resolution is 1o lat x 1o long (about 70x50 sq. mi.)

  • Standard simulation; compare w/ observations to assess confidence in the model

  • Set U.S. or N. American anthropogenic emissions to zero a quantify U.S. backgroundandNorth American background

  • Difference between U.S. background and North American background a Canadian+Mexican pollution enhancement (CANMEX)

  • (4) Set global anthropogenic emissions to zero a quantify natural background

3-D model structure


Transboundary influences on us background ozone

Background ozone is important for setting the standard

Natural background

from GEOS-Chem

Data from Fiore et al. [JGR, 2003b] for the period Mar-Oct 2001

NA background

from GEOS-Chem

NA background

from MOZART-2

CASTNet sites observations

GEOS-Chem at CASTNet

Background is not directly measurable

and needs to be estimated from models


Transboundary influences on us background ozone

NA background – no anthropogenic emissions in North America

US background – no anthropogenic emissions in the US

The national totals of CAN and MEX are small, but there are

non-negligible emission sources close to the border


Transboundary influences on us background ozone

NA background (without NA anthropogenic emissions)

JJA 2001 mean, based on daily-8h-max

US background (without US anthropogenic emissions)


Transboundary influences on us background ozone

Canadian and Mexican influences (ppb)

(JJA mean, based on daily-8h-max)

Selected rural measurement sites under CANMEX influences, avoiding mountain-top sites and sites with complex topography, traffic influence, and missing data

Enhancement to NA background is found

In the Northeast and Southwest US


Transboundary influences on us background ozone

Canadian enhancement in the Northeast (ppb)

(JJA mean, based on daily-8h-max)

•Rural sites under CAN influence

The largest mean Canadian enhancement is 8.8 ppb

(among all US grid boxes)


Transboundary influences on us background ozone

Mexican enhancement in the Southwest (ppb)

(JJA mean, based on daily-8h-max)

•Rural sites under MEX influence

The largest mean Mexican enhancement is 13.1 ppb

(among all US grid boxes)


Transboundary influences on us background ozone

Williamson

Buffalo

Unionville

Westfield

Kane Exp Forest

Lykens

CAN enhancement at selected sites in the Northeast

close to Canadian sources

Daily-8h-max time series for these six locations follow …


Transboundary influences on us background ozone

The largest episodic CAN enhancement at Unionville, MI (34 ppb) increases US background to 47 ppb (red circle)

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Westfield, NY

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Williamson, NY

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Kane Exp Forest, PA

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Lykens, OH

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Buffalo, NY: At Buffalo, the CAN influence is frequently above 10 ppb, and US background is frequently above 30 ppb

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

For Buffalo, EPA has shown that Canadian sources contribute 59% to ozone precursors on peak ozone days

(Slide from EPA presentation)


Transboundary influences on us background ozone

Williamson

Buffalo

Unionville

Westfield

Stow

Kane Exp Forest

Lykens

Wash. Crossing

Greenbelt

High episodic CAN contributions are experienced as far south and east as Eastern MA, New Jersey, and the Washington DC area

Daily-8h-max time series for these more distant locations follow …


Transboundary influences on us background ozone

Stow, MA

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Washington Crossing, NJ

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Greenbelt, MD

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which CAN enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Alpine, CA: The situation in the Southwest is different from the Northeast; there is a larger mean enhancement but fewer sharp episodes. MEX influence is frequently above 10 ppb, and US background is frequently above 30 ppb

Measurement Std-run US-backgroundNA-backgroundCANMEX

Inverted black triangles show days in which MEX enhancement is >10 ppb and observed ozone concentration is >80 ppb


Transboundary influences on us background ozone

Canadian influence is >10 ppb on some peak ozone days (>80 ppb)

Canadian influence is always <10 ppb on peak ozone days (>80 ppb)

Untagged color boxes have max surface ozone <= 80 ppb

CAN influence is important for areas near the Great Lakes and the Northeast coast

Max CAN contribution on peak ozone days is 23 ppb among boxes shown as:■


Transboundary influences on us background ozone

Canadian influence is >10 ppb on some peak ozone days (>75 ppb)

Canadian influence is always <10 ppb on peak ozone days (>75 ppb)

Untagged color boxes have max surface ozone <= 75 ppb


Transboundary influences on us background ozone

Canadian influence is >10 ppb on some peak ozone days (>70 ppb)

Canadian influence is always <10 ppb on peak ozone days (>70 ppb)

Untagged color boxes have max surface ozone <= 70 ppb

Note that as the reference ozone value is decreased, increasingly larger areas of the Southeast and industrial Midwest are influenced


Transboundary influences on us background ozone

Canadian influence is >5 ppb on some peak ozone days (>80 ppb)

Canadian influence is always <5 ppb on peak ozone days (>80 ppb)

Untagged color boxes have max surface ozone <= 80 ppb


Transboundary influences on us background ozone

Canadian influence is >5 ppb on some peak ozone days (>75 ppb)

Canadian influence is always <5 ppb on peak ozone days (>75 ppb)

Untagged color boxes have max surface ozone <= 75 ppb


Transboundary influences on us background ozone

Canadian influence is >5 ppb on some peak ozone days (>70 ppb)

Canadian influence is always <5 ppb on peak ozone days (>70 ppb)

Untagged color boxes have max surface ozone <= 70 ppb

At CAN = >5 ppb and ozone = >70 ppb, much of the eastern US is influenced, even into North Carolina


Transboundary influences on us background ozone

Contribution of CAN pollution to exceedances of different levels of ozone concentration (I)

Number of data points exceeding specified values of CAN enhancement and ozone concentration (cumulative)

93

50

28

Y:

527

280

138

854

2936

1679

70 75

X:

Includes all US grid boxes within [36N-48N, 88W-66W] (15,180 data points)

30


Transboundary influences on us background ozone

Scatter plot based on timeseries at the gridboxes with

Ozone > 80ppb and Canadian influence > 5ppb

71

43

28

138

359

225

1409

916

540

Contribution of CAN pollution to exceedances of different levels of ozone concentration (II)

Number of data points exceeding specified values of CAN enhancement and ozone concentration (cumulative)

Sorted to include only the 56 grid boxes that had at least one case of X >80 ppb and Y >5 ppb, i.e., under some Canadian influence (5,152 data points)

31


Transboundary influences on us background ozone

Mexican influence is >10 ppb on some peak ozone days (>80 ppb)

Mexican influence is always <10 ppb on peak ozone days (>80 ppb)

Untagged color boxes have max surface ozone <= 80 ppb

MEX influence is important for southern California and parts of Arizona and Texas

Max MEX contribution on peak ozone days is 18 ppb among boxes shown as:■


Transboundary influences on us background ozone

Mexican influence is >10 ppb on some peak ozone days (>75 ppb)

Mexican influence is always <10 ppb on peak ozone days (>75 ppb)

Untagged color boxes have max surface ozone <= 75 ppb


Transboundary influences on us background ozone

Mexican influence is >10 ppb on some peak ozone days (>70 ppb)

Mexican influence is always <10 ppb on peak ozone days (>70 ppb)

Untagged color boxes have max surface ozone <= 70 ppb


Transboundary influences on us background ozone

Mexican influence is >5 ppb on some peak ozone days (>80 ppb)

Mexican influence is always <5 ppb on peak ozone days (>80 ppb)

Untagged color boxes have max surface ozone <= 80 ppb


Transboundary influences on us background ozone

Mexican influence is >5 ppb on some peak ozone days (>75 ppb)

Mexican influence is always <5 ppb on peak ozone days (>75 ppb)

Untagged color boxes have max surface ozone <= 75 ppb


Transboundary influences on us background ozone

Mexican influence is >5 ppb on some peak ozone days (>70 ppb)

Mexican influence is always <5 ppb on peak ozone days (>70 ppb)

Untagged color boxes have max surface ozone <= 70 ppb

At MEX = >5 ppb and ozone = >70 ppb, MEX influence extends into Nevada, New Mexico, and NW Texas


Transboundary influences on us background ozone

Contribution of MEX pollution to exceedances of different levels of ozone concentration (I)

Number of data points exceeding specified values of MEX enhancement and ozone concentration (cumulative)

53

28

14

Y:

49

271

109

2453

1002

413

70 75

X:

38

Includes all US grid boxes within [26N-42N, 120W-90W] (34,960 data points)


Transboundary influences on us background ozone

Scatterplot based on timeseries at gridboxes with

Ozone > 80 ppb & Mexican enhancement > 5 ppb

Contribution of MEX pollution to exceedances of different levels of ozone concentration (II)

Number of data points exceeding specified values of MEX enhancement and ozone concentration (cumulative)

14

43

27

155

90

49

379

223

125

Sorted to include only the 15 grid boxes that had at least one case of X >80 ppb and Y >5 ppb, i.e., under some Mexican influence (1,380 data points)

39


Transboundary influences on us background ozone

CONCLUSIONS

  • Transboundary pollution from Canada and Mexico increases the mean background surface ozone concentration in the US in JJA by 1-13 ppb.

  • The largest Canadian enhancement is 8.8 ppb (JJA mean), with an episodic maximum of 34 ppb (at Unionville, MI) in the daily-8h-max time series.

  • The largest Mexican enhancement is higher, 13.1 ppb (JJA mean), but the maximum in the daily-8h-max time series is smaller (21 ppb, not shown).

  • For peak ozone cases, the US background can be >30 ppb and even 40 ppb due to transboundary influences.

  • Transboundary pollution can contribute significantly (up to 23 ppb in the Northeast and 18 ppb in the Southwest) to peak ozone levels (in this case, defined as >80 ppb).

  • Canadian contributions on peak days (>70, > 75, or > 80 ppb ozone) can exceed 10 ppb as far from Canada as near Washington, DC; central New Jersey, and eastern Massachusetts; Mexican contributions can be consistently higher in some cases, but focused on closer areas of S. California, S. Nevada, and western to central Arizona.

  • Cross-border contributions of these magnitudes impose significant penalties for some regions of the country, i.e., in order to achieve a tightened ozone standard, parts of MI, NY, PA, and other Northeastern and Midwestern locations would have to get substantial additional emission reductions, depending on location, to offset the Canadian influence.


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