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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
10th Annual CMAS Conference 1 Chapel Hill, NC
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
10th Annual CMAS Conference 2 Chapel Hill, NC
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
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
10th Annual CMAS Conference 9 Chapel Hill, NC
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
10th Annual CMAS Conference 10 Chapel Hill, NC
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
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
10th Annual CMAS Conference 14 Chapel Hill, NC
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
10th Annual CMAS Conference 18 Chapel Hill, NC
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