Background Air Quality in the United States Under Current and Future Emissions Scenarios

Zachariah Adelman, Meridith Fry, J. Jason WestDepartment of Environmental Sciences and EngineeringUniversity of North Carolina

Pat Dolwick, Carey JangOffice of Air Quality Planning and StandardsUnited States Environmental Protection Agency

Presented at the 10th Annual CMAS ConferenceOctober 24-26, 2011 Chapel Hill, NC

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Motivation and Objectives• Will U.S. background air pollutant concentrations

increase in the future?• Objectives:

– Gather and process latest IPCC inventories for current and future year emissions estimates

– Use MOZART-4 to simulate future air quality resulting from climate change mitigation emissions scenarios

– Estimate background air quality in the U.S. by “zeroing-out” North American anthropogenic emissions

– Downscale global modeling results to produce boundary conditions for regional modeling

Methods and Data• Chemistry-Transport Model: MOZART-4• Meteorology: 2005 GEOS-5 1.9°x2.5°• Emissions Inventory: 2005 and 2030 Representative

Concentration Pathways (RCP)– RCP8.5 – Business as usual emissions– RCP4.5 – Best estimate emissions reduction– RCP2.6 – Maximum emissions reduction

• Zero-out North America (ZONA): – U.S., Canada, Mexico anthropogenic emissions set to zero

• Includes near-shore (< 50km) shipping, aircraft < 3km, and fertilizer

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Methods and Data• Emissions processing with

custom IDL and NCL scripts– Speciate with RCP to

MOZART-4 conversion factors– Temporalize with RETRO

monthly profiles– Regrid to GEOS-5 grid– Merge natural and

anthropogenic sectors and create MOZART-ready files

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SpeciateSpeciate

TemporalizeTemporalize

RegridRegrid

MergeMerge

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RCP MOZART-4 SpeciesMOZART RCP Species

CH3OH 0.5*alcohols

C2H5OH 0.5*alcohols

CH2O formaldehyde

C2H6 ethane

C3H8 propane

BIGALK butanes+pentanes+hexanes

C2H4 ethene

C3H6 propene

BIGENE butane+other_alkenes_and_alkynes

MOZART RCP Species

C2H2 ethyne

MEK 0.5*ketones

CH3COCH3 0.5*ketones

HCOOH 0.5*acids

CH3COOH 0.5*acids

TOLUENE benzene+toluene+xylene+trimethyl_benzene+other_aromatics

C10H16 terpenes

ISOP isoprene

OC1 OC

CB1 BC

MOZART-4 Simulations

• Simulations using meteorology for 2005

• July 1 – December 31, 2004 spin-up

• Fixed methane concentrations

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MOZART CH4 (ppb)

2005 RCP8.5 1,783

2030 RCP8.5 2,132

2030 RCP4.5 1,830

2030 RCP2.6 1,600

2005 RCP8.5 ZONA 1,783

2030 RCP8.5 ZONA 2,132

2030 RCP4.5 ZONA 1,830

2030 RCP2.6 ZONA 1,600

Emissions Summaries

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NOxNOx

NMVOCNMVOC

GlobalGlobal USUS

Emissions Summaries

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BCBC

OCOC

GlobalGlobal USUS

Base Annual Max 8-hr O3 Results

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RCP 8.5 2005RCP 8.5 2005 RCP 8.5 2030RCP 8.5 2030

RCP 4.5 2030RCP 4.5 2030 RCP 2.6 2030RCP 2.6 2030

ZONA Annual Max 8-hr O3 Results

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RCP 8.5 2005RCP 8.5 2005 RCP 8.5 2030RCP 8.5 2030

RCP 4.5 2030RCP 4.5 2030 RCP 2.6 2030RCP 2.6 2030

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8-hr O3 ResultsAnnual Mean 8-hr O3 Annual Max 8-hr O3

Global US Global US

RCP8.5 2005 28.8 42.4 178.1 170.4RCP8.5 2030 30.2 43.1 166.1 118.9RCP4.5 2030 29.0 40.8 142.4 133.8RCP2.6 2030 27.3 39.3 156.1 138.1RCP8.5 2005 ZONA 26.9 30.1 177.7 50.1RCP8.5 2030 ZONA 28.0 31.6 165.2 52.8RCP4.5 2030 ZONA 27.4 30.9 164.9 51.6RCP2.6 2030 ZONA 25.5 29.1 156.0 49.3

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Background U.S. mean 8-hr O3Annual Winter Spring Summer Fall

RCP8.5 2005 30.1 31.5 32.9 (5.4) 26.5 (5.6) 29.3 (4.8)RCP8.5 2030 31.6 33.3 34.4 (5.7) 27.8 (6.0) 30.8 (5.2)RCP4.5 2030 30.9 32.6 33.8 (5.6) 27.1 (5.8) 30.2 (5.1)RCP2.6 2030 29.1 31.0 31.6 (5.3) 25.4 (5.4) 28.2 (4.6)

Annual Winter Spring Summer Fall

RCP8.5 2005 71% 89% 71% 58% 70%RCP8.5 2030 73% 85% 74% 63% 72%RCP4.5 2030 76% 83% 77% 68% 75%RCP2.6 2030 74% 83% 75% 65% 73%

Background contribution to U.S. mean 8-hr O3

U.S. Summer Daily Max 8-hr O3 Frequency Distribution

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Base Annual Max 24-hr non-dust PM2.5* Results

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RCP 8.5 2005RCP 8.5 2005 RCP 8.5 2030RCP 8.5 2030

RCP 4.5 2030RCP 4.5 2030 RCP 2.6 2030RCP 2.6 2030

*(SO4, NO3, NH4, SOA, EC, and OC)

ZONA Annual Max 24-hr non-dust PM2.5 Results

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RCP 8.5 2005RCP 8.5 2005 RCP 8.5 2030RCP 8.5 2030

RCP 4.5 2030RCP 4.5 2030 RCP 2.6 2030RCP 2.6 2030

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PM2.5 Results

Annual Mean 24-hr PM2.5 Annual Max 24-hr PM2.5

Global US Global US

RCP8.5 2005 1.2 2.7 375.3 79.8RCP8.5 2030 1.1 1.9 320.0 57.2RCP4.5 2030 1.1 1.8 238.7 59.0RCP2.6 2030 1.1 2.0 453.3 66.0RCP8.5 2005 ZONA 1.1 0.5 375.3 25.7RCP8.5 2030 ZONA 1.1 0.5 319.9 25.9RCP4.5 2030 ZONA 1.1 0.5 319.8 25.9RCP2.6 2030 ZONA 1.0 0.5 453.3 28.2

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Speciated U.S. Annual Max PM2.5SO4 NO3 NH4 SOA BC OC Total

RCP8.5 2005 8.4 21.9 25.9 0.2 4.8 18.7 79.88RCP8.5 2030 6.5 14.0 16.6 0.2 1.2 18.7 57.24RCP4.5 2030 2.8 16.8 17.4 0.2 4.1 17.7 58.98RCP2.6 2030 5.0 14.8 18.8 0.2 5.2 22.0 65.95RCP8.5 2005 ZONA 1.9 0.7 3.1 0.2 1.2 18.7 25.66RCP8.5 2030 ZONA 2.0 0.7 3.1 0.2 1.2 18.7 25.87RCP4.5 2030 ZONA 1.9 0.9 3.1 0.2 1.2 18.7 25.92RCP2.6 2030 ZONA 1.9 0.7 3.1 0.2 1.4 20.9 28.18

CONUS36 CMAQ Annual Max 1-hr O3 BCs

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RCP8.5 2005RCP8.5 2005 RCP8.5 2030RCP8.5 2030

RCP4.5 2030RCP4.5 2030 RCP2.6 2030RCP2.6 2030

S NE W

S NE W

S NE W

S NE W

CONUS36 CMAQ Annual Max 1-hr PM2.5 BCs

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RCP8.5 2030RCP8.5 2030

RCP4.5 2030RCP4.5 2030 RCP2.6 2030RCP2.6 2030

S NE W

S NE W

S NE W

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Conclusions

1. These results indicate that only the emissions scenario that pursued extremely aggressive climate change mitigation (RCP2.6) lead to reductions in global O3 burden and U.S. background O3 and PM2.5 concentrations.

2. Annual maximum U.S. 8-hr O3 concentrations and frequency of high (> 70 ppb) 8-hr O3 events are predicted to decrease in all simulated future emissions cases, likely due to domestic emission controls

3. Contribution of background to total U.S. O3 concentrations predicted to increase in the future (~2-5% to annual mean and up to 10% to summer mean): combination of rise in transported O3 and drop in domestic O3 production

Future Work

• Probe MOZART process-level output to gain a better understanding of the differences between the RCP results

• Run CMAQ with the downscaled 2005 and 2030 BCs and recalculate U.S. background concentrations

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