Effect of Global Change on U.S. Air Quality

Murazaki and Hess, JGR 2006

Acknowledgements:

- L. Emmons, J.F. Lamarque, J. Orlando, G. Tyndall, S. Walters, X.X. Tie

-N. Mahowald

• Import of ozone to the U.S.

• Ozone produced over the U.S.– Repartitioning of NOy budget– Increased water vapor– Changes in clouds and photolysis rates– Changes in lightning– Changes in meteorology

• Planetary Boundary Layer• Synoptic Storms Frequency• Great Plains low-level jet

Effect of Global Change

Methodology

• Ran MOZART For Present (1990-2000) and Future Cases (2090-2100)– Winds generated by the CSM forced w/ IPCC A1

scenarios– Emissions fixed at 1990 levels

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Simulated O3 Measured O3

Model minus Measurements

0

20

40

60

80

100

120

0 20 40 60 80 100 120

Western U.S.M

odel (ppbv)

EPA (ppbv)

Eastern U.S.

Figure 3. Correlation of daily maximum 8-hour surface ozone concentrations between model and measurements at EPA AIRS measurement sites in eastern U.S. (squares) and western U.S. (circles) during JJA. The east-west division is assumed to be at 100W.

Model-Measurement Correlation

Zonal Average Future minus Control Surface O3 (JJA)

Ozone Change (ppbv)

Figure 1.

Future minus Control Surface O3 (JJA)

Figure 12. As in Figure 4, but for differences in 8 hour maximum ozone concentration (ppbv): (a) ozone (b) contribution of background ozone; (c) contribution from ozone produced from U.S. NOx emissions; (d), (e), and (f) shows the respective differences between the future and control simulations.

+.7% ; +2.8% +5% ; +4.1%-11.5% ; -9.7%

Ozone Imported Ozone U.S. Ozone

What Processes Are Responsible for the Ozone Response?

1) Temperature Increases

2) Water Increases

a) b)

Changes in NOx (ppbv) Changes in PAN (ppbv)

Repartitioning of NOy

6.3 % 4.6 % -23.3 % -22.9 %

Water Vapor Increases

O3 + hv O(1D) + O2 O(1D) + H2O 2 OH OH + CO (+ O2 +M) HO2 + CO2 (+M) HO2 + O3 OH + 2O2 HO2 + NO NO2 + OH NO2 + hv -> NO + O O + O2 + M -> O3 + M

LOW NOx

HIGH NOx

Vertically integrated cloud water Changes in J_O(1D) (g) from the surface to 700hPa.

Changes in Clouds

-20.7 % -28.1 % +2.8% +4.8%

(Del Genio and Wolf [2000] show observationally that the low-cloud liquid water path over the Great Plains decreases with increasing temperature due to a decrease in cloud thickness.)

Temperature Increase V. High Increase

Water Vapor Increase V. High Increase/Decrease Synoptic Freq. Decrease High ?Background O3 Decrease High Decrease

PBLH ? V. Low ?Precip. ? V. Low ?Lightning Increase V. Low Increase

Clouds Decrease

(Low Levels) Low Increase

Circulation

Changes V. Low ?

Change Confidence O3 Response

Mickley et al., 2004

Changes in Synoptic Frequency

Changes in Frequency of Synoptic Systems - Confident/Uncertain

2-6 day bandpassed frequencies of O3 / CO decrease by 10% / 7.5 %O3 autocorrelation time increases from .13 to .26 at 2 days in future

OZONE Asian CO

b)

Figure 14. Cumulative probability of a) daily maximum 8-hour ozone (ppbv) and b) CO (ppbv).

a)

b)

Ozone

CO

b)

Figure 17. Same as figure 15 except at 70o W.

Ozone Export

Figure 11. As in Figure 4, but for the difference in net ozone production (in 105 molec. cm-3 s-1).

c)

Figure 10. As in Figure 4, but for the differences in (ppbv) (c) OH (pptv) and d) H2O2 (ppbv).

d)

From Jacob et al, 1999: Changes in ozone concentrations over the U.S. relative to 1985 values when 25% reduction in anthropogenic NOx and NMHC are implemented with 1985 Asian emissions (left) and 2010 Asian emissions (right).

Imported Ozone versus Local Controls

Collins et al., 2003

Figure 7. As in Figure 4, but for the difference in vertically integrated lightning NOx production (Tg N yr-1).

Changes in Lightning

% Stratospheric Influence

Stratospheric O3 Tracer

XNOX Methodology

BACKGROUND OZONE U.S. Summer

Our Method Fiore et al, 13-17 LT

O3 produced outside U.S. BL

O3 not produced by U.SNOx emissions

Jaffe et al., Geophys. Res. Letters, 2003

Mean O3 has increased along the west coast of the U.S. during Spring

Conclusion: Along the U.S. west coast, springtime O3 has increased by ≈ 0.5 ppbv/yr

Marine Boundary Layer Elevated Data Sets

Figure 13. As in Figure 4, but for the average difference between the future and control simulations of the number of days the 8 hour maximum ozone concentration in a year is greater than 80 ppbv.

Difference in days 8-hour O3 > 80 ppbv