1. Improving PM2.5 forecasting ability of Hi-Res in southeastern United States
Yongtao Hu, Jaemeen Baek, M. Talat Odman and Armistead G. Russell
School of Civil & Environmental Engineering
Georgia Institute of Technology
Presented at the 7th Annual CMAS Conference, October 7th, 2008
Georgia Institute of Technology

2. Georgia Institute of Technology
Outline
The Hi-Res air quality forecasting system.
2007 O3 and PM2.5 performance.
Performance investigation using PM2.5 components measurements.
New Secondary Organic Aerosol (SOA) module.
Experiment with new SOA module and results.
Georgia Institute of Technology

3. Snapshots from Hi-Res homepage: http://forecast.ce.gatech.edu
Hi-Res: forecasting ozone and PM2.5 at a 4-km resolution in metro Atlanta area
Three grids:
36-km (72x72)
12-km (72x72)
4-km (99x78)
34 vertical layers used in WRF
13 layers in CMAQ
Snapshots from Hi-Res homepage:
Georgia Institute of Technology

4. Ambient Monitoring Sites for Performance Evaluation
2 Search
4 ASACA
1 STN
Speciated PM2.5
observed at 7 sites
SLAMS sites
7 PM2.5
10 O3
Georgia Institute of Technology

5. 2007 O3 Performance: Hi-Res vs. EPD’s
4-km Forecast
EPD Ensemble Forecast
False Alarms
Hits
Correct Nonevents
Missed Exceedences
MNB
8.5%
MNE
19%
MNB
9.0%
MNE
18%
Georgia Institute of Technology

6. Forecasted vs. Observed O3
Rained a lot in August. Soil moisture wetter than typical.
Cooler temperatures
Less A/C use => Less EGU NOx (about 30% of total NOx)
Also thundershowers are hard to model.
Georgia Institute of Technology

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Ozone Season 2006 vs. 2007
Rained a lot in August. Soil moisture wetter than typical.
Cooler temperatures
Less A/C use => Less EGU NOx (about 30% of total NOx)
Also thundershowers are hard to model.
Georgia Institute of Technology

8. 2007 PM2.5 Performance: Hi-Res vs. EPD’s
Our 4-km Forecast
EPD Ensemble Forecast
MNB
-37%
MNE
44%
MNB
8.6%
MNE
28%
Georgia Institute of Technology

9. Forecasted vs. Observed PM2.5
OC underestimation in June-July-August
Cooler temperatures in September
Georgia Institute of Technology

10. Georgia Institute of Technology
Summer 2006 vs. 2007
OC underestimation in June-July-August
Cooler temperatures in September
Georgia Institute of Technology

11. Forecasted vs. Observed PM2.5
OC underestimation in June-July-August
Cooler temperatures in September
Georgia Institute of Technology

12. Forecasted vs. Observed PM2.5 Components
Ammonium
Forecasted vs. Observed PM2.5 Components
Sulfate
Organic Carbon
Nitrate
Elemental Carbon
Georgia Institute of Technology

13. Georgia Institute of Technology
Organic Carbon
G-F wild fire
Under-estimation
Over-prediction
Georgia Institute of Technology

14. New SOA module* developed at Georgia Tech
Included processes:
SOA species in CMAQ:
SOA partitioned from Anthropogenic VOCs’ oxidations (8 SVOCs)
From monoterpenes (2 SVOCs)
From isoprene (2 SVOCs added)
From sesquiterpenes (1 SVOC added, gas phase oxidation reactions added for α-caryphyllene, β-humulene and other sesquiterpenes)
Aging of all semi-volatile organic carbons (SVOCs) added
AORGAJ and AORGAI
AORGBJ and AORGBI
AORGBISJ and AORGBISI
AORGBSQJ and AORGBSQI
AORGAGJ and AORGAGI
HSVOC
LSVOC
Aerosol
Aging process:
+OH,+O3
*Baek et al. 2008, manuscipt in preparation.
Georgia Institute of Technology

15. Simulated Secondary Organic Contributions
From Monoterpene
From Isoprene
From Sesquiterpene
From Antropogenic VOCs
From Aged SVOCs
Compare to Primary
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16. PM2.5 performance improves Georgia Institute of Technology

17. before and after OC performance Georgia Institute of Technology

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Summary
2007 Ozone forecasts are good.
Overall bias is +8.5% and error is 19%
PM2.5 forecasts are not very accurate.
May-September bias is -37% and error is 44%
FL-GA wildfires of 2007 impacts
Performance is much better in Fall and Spring
Wintertime PM2.5 was overestimated, Summertime PM2.5 was underestimated
PM2.5 components
Inorganic components are generally OK
organic components are worse
SOA formation is possibly underestimated
New SOA module “improves” the summer PM2.5 forecasts
Better emissions estimations for organic PM is critical
Georgia Institute of Technology

19. Georgia Institute of Technology
Acknowledgements
Georgia EPD has funded the forecasts.
Dr. Michael Chang, EAS of Georgia Tech.
Our ASACA team: Sivaraman Balachandran, Emily Katherine Lantrip, Laura Anne Parry, ... for ASACA data.
Southern Company for SEARCH data.
Georgia Institute of Technology

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Performance Metrics
False Alarms
Hits
Correct Nonevents
Missed
Exceedences
Forecast
Observation
Georgia Institute of Technology

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