Prediction of Future North American Air Quality
Gabriele Pfister, Stacy Walters, Mary Barth,
Jean-Francois Lamarque, John Wong
Atmospheric Chemistry Division, NESL/NCAR
Greg Holland, James Done, Cindy Bruyere
Meteorological Mesoscale Division, NESL/NCAR
Jerome Fast, Po-Lun Ma
Pacific Northwest Laboratory, PNNL
Objectives
Average number of days (%) during May-Sep 1995-2000 and 2005-2010
when the 8-hour ozone NAAQS of 75 ppbV was exceeded.
(EPA Monitoring Network)
“Emission controls in the U.S. have lead to significant reductions in air pollution, but many regions in the country still experience levels
of pollutants above national health standards ”
“There is growing recognition that development of optimal control strategies for key pollutants (O3, PM2.5) requires
assessment of potential future climate conditions and their influence on the attainment of air quality objectives”
Objectives
“There is growing recognition that development of optimal control strategies for key pollutants (O3, PM2.5) requires
assessment of potential future climate conditions and their influence on the attainment of air quality objectives”
Δ S
urf
ace
O3 (
%)
ove
r C
A
Stei
ner
et
al.,
20
06
Global trop. O3 Burden (Young et al., 2013)
Eastern U.S. (Hogrefe et al., 2004) Tai et al., 2012
• Increased temperatures & stagnation events • Changes in clouds and solar insolation • Increased methane – enhanced O3 background • Feedbacks of climate on biogenic & fire emissions • Changes in anthropogenic emissions
Objectives
Limitations of past studies:
“There is growing recognition that development of optimal control strategies for key pollutants (O3, PM2.5) requires
assessment of potential future climate conditions and their influence on the attainment of air quality objectives”
Wu et al., 2008
Coarse resolution
Limited number of years
Courtesy: NOAA
Objectives
High Resolution Regional Chemistry-Climate Simulations
Future changes in weather and air quality over North America
Effects of changing emissions and changing climate on AQ
Feedbacks between chemistry and climate
Differences in climate metrics when downscaling from
global or larger scale simulations with different physics
Sensitivity of predictions to initial conditions
NSF EASM - Developing a Next-Generation Approach to Regional Climate Prediction at High Resolution (PI Greg Holland)
NCAR ASD - Accelerated Scientific Discovery Proposal 2012 (PI Gabriele Pfister)
Objectives
Regional CTM– WRF-Chem
Weather Research and Forecasting Model with Chemistry
Fully coupled regional chemical transport model
Embedded in WRF
Variety of Chemical Schemes (incl. RADM2, RACM, CBMZ, MOZART-4,…)
Different Aerosol schemes (bulk, modal), sectional)
Biogenic emission schemes (incl. MEGAN)
Photolysis Schemes (incl. TUV, FTUV)
Online dry deposition (incl. Wesely)
MOZART, WRF-Chem and EPA Network Surface O3
June 19-30, 2008
Main WRF-Chem Website:
http://ruc.noaa.gov/wrf/WG11/
NCAR/ACD WRF-Chem Website:
http://www.acd.ucar.edu/wrf-chem/
13 years present (1996-2007) and future (2046-2057)
Season: 1 April – 1 Oct
12 x 12 km2 (697 x 394); 51 vertical levels (up to 10 hPA)
Gas-Phase Scheme: Reduced Hydrocarbon Scheme (40 species)
Aerosols: Modal Aerosol Model (MAM; 33 species, +SOA)
Direct/indirect aerosol effects
CAM-5 microphysics and PBL Scheme
IPCC A2 Climate Scenario, RCP8.5 Emission Scenario
WRF-Chem NRCM-Chem
Simulation Period Climate Emissions IC & BC Chemistry
SIMPRES Present Present 2000 Present REDHC/MAM
SIMFUT Future Future 2050 Future REDHC/MAM
SIMFUT_EMIS Future Future 2000 Future REDHC/MAM
SIMMET Future Future - Future -
10 years + 3 years/simulation with initial start date changed
• Meteorological Initial & Boundary Conditions Downscaled from NRCM @ 36 x 36 km2 [Done et al., 2012]
Done et al. (2012), NCAR/TN-490+STR, 28pp.
36 x 36 km2
12 x 12 km2
NRCM-Chem - IC & BC
NRCM-Chem – Downscaling Meteorology
Mean JJA Temperature @ 2 m for Present
NRCM 36 km x 36 km NRCM-Chem 12 km x 12 km
Mean JJA Temperature @ 2 m for Present
NRCM 36 km x 36 km NRCM-Chem 12 km x 12 km
NRCM-Chem – Downscaling Meteorology
Mean JJA Temperature @ 2 m for Future
NRCM 36 km x 36 km NRCM-Chem 12 km x 12 km
NRCM-Chem – Downscaling Meteorology
• Chemical Initial and Lateral Boundary Conditions CAM-Chem RCP 8.5 [Lamarque et al., 2011); Monthly means for 2000 and 2050
Lamarque et al. , Climatic Change, 2011.
• Upper Chemical Boundary Conditions for O3, N2O, CO, ...
NRCM-Chem - IC & BC
• IPCC RCP 8.5 Scenario:
NOx emissions reduced by -60% over domain (-10% globally) by 2050
Domain Totals for JJA
NRCM-Chem - Emissions
• IPCC RCP 8.5 Scenario (8.5 W m-2 radiative forcing by 2100)
NOx emissions reduced by -60% over domain (-10% globally) by 2050
• Global 0.5° IPCC emissions used in CAM-Chem
re-grid in 2° x 2° segments to 0.1° using EDGAR-4.1# spatial distribution
mass-conserving mapping to NRCM-Chem domain
# http://edgar.jrc.ec.europa.eu
Global Emissions 0.5° NRCM-Chem 12 km EPA NEI 2005 4km->12km
NRCM-Chem - Emissions
Fire Emissions:
NCAR Fire Model FINN
10-year Climatology
Same for Present & Future
Biogenic Emissions:
Online MEGAN
No change in land cover/use
Radiation and T dependence
LAI, TS and PAR climatology for plant history
NO Fire Emissions - Time Series
Isoprene Emissions, July present
NRCM-Chem - Emissions
Present Time Surface Ozone – Evaluation
JJA Surface Ozone Daytime Nighttime
NRCM-Chem: 13 years present time AQS Surface Ozone Monitoring Sites, 1996-2005 (http://www.epa.gov/ttn/airs/airsaqs/)
Present Time Surface Ozone – Evaluation
JJA Surface Ozone Average Diurnal Cycle
Prediction of Future Surface Ozone
Present
Future Climate +
Future Anth. Emissions
MD8hr
Prediction of Future Surface Ozone
Present
Future Climate +
Present Anth. Emissions
MD8hr
Prediction of Future Surface Ozone
MD8hr
Present Future Climate + Emissions Future Climate Only
Days with Ozone - NAAQS Exceedances
-99%
+64%
-98%
+45%
Present
MD8hr > 65 ppbV MD8hr > 75 ppbV
Future (Climate + Emissions)
Future (Climate Only)
Meteorological Drivers – 2m Temperature
Daytime, Confidence Level: 95%
(Present) Daily Mean 2m Temperature (Future-Present)
13-year JJA Average
Individual daily mean values
30°C 40°C
Meteorological Drivers – Heat Index (HI)
HI Day = Day with HImin > 80°F and HImax <105°F
Temperature (K) & Rel. Humidity (%) Heat Index Days
Futu
re-P
rese
nt
P
rese
nt
Shown are Daily Mean T & RH, # HI days in JJA
Meteorological Drivers – Isoprene emissions
Confidence Level: 95%
(Present) Daily Total Isoprene Emissions (Future-Present)
16.4 18.7 TgC
(Present) Daytime Solar Radiation (Future-Present)
Meteorological Drivers – Rainfall
Confidence Level: 75%
(Present) JJA Total Rainfall (Future-Present)
13-year JJA Average
JJA Rainfall Totals for each year
Meteorological Drivers – Wind & Solar Radiation
(Present) Daily Mean Wind Speed (Future-Present)
(Present) Ventilation Index (unvented hours/day) (Future-Present)
Global and Regional Predictions
Long Range Transport and Background Ozone
CAM-Chem Present Time Surface Ozone (16-22 UTC)
Future - Present
Predictions: Global Regional
CAM-Chem
NRCM-Chem
16-22 UTC
JJA - Present Surface Afternoon Ozone
Predictions: Global Regional
16-22 UTC
CAM-Chem
NRCM-Chem
JJA – Future-Present Surface Afternoon Ozone
Global and Regional Predictions
NRCM-Chem CAM-Chem
Present Future-Present
• Reducing surface Ozone over the U.S. can be achieved by strong emission reductions, while the impacts of climate act to increase surface ozone by 2050 in parts due to increased temperature, solar radiation and stagnation events and higher background levels.
• Albeit biases in absolute values, global and regional models predicts similar changes on the larger scale. Locally, however, differences can be significant.
Much more to look into: Future Changes in Air Quality – Impacts of Climate and Emissions
Future Changes in Climate and Weather
Extreme Events
Dynamical Downscaling of Meteorology and Chemistry
Chemistry-Climate Feedbacks
Sensitivity to Initial Conditions etc. etc. etc.
Conclusions and Next Steps
QUESTIONS / SUGGESTIONS
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