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