Improving PM2.5 forecasting ability of Hi-Res in southeastern United States

Yongtao Hu, Jaemeen Baek, M. Talat Odman and Armistead G. RussellSchool of Civil & Environmental EngineeringGeorgia Institute of Technology

Presented at the 7th Annual CMAS Conference, October 7th, 2008

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.

Snapshots from Hi-Res homepage: http://forecast.ce.gatech.eduThree grids:36-km (72x72)12-km (72x72)4-km (99x78)34 vertical layers used in WRF13 layers in CMAQHi-Res: forecasting ozone and PM2.5 at a 4-km resolution in metro Atlanta area

Ambient Monitoring Sites for Performance Evaluation

2007 O3 Performance: Hi-Res vs. EPDs4-km ForecastEPD Ensemble ForecastHitsFalse AlarmsCorrect NoneventsMissed Exceedences

MNB8.5%MNE19%

MNB9.0%MNE18%

Forecasted vs. Observed O3

Ozone Season 2006 vs. 2007

2007 PM2.5 Performance: Hi-Res vs. EPDsOur 4-km ForecastEPD Ensemble Forecast

MNB-37%MNE44%

MNB8.6%MNE28%

Forecasted vs. Observed PM2.5

Summer 2006 vs. 2007

Forecasted vs. Observed PM2.5

Forecasted vs. Observed PM2.5 ComponentsSulfateAmmoniumNitrateElemental CarbonOrganic Carbon

New SOA module* developed at Georgia Tech*Baek et al. 2008, manuscipt in preparation.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 -caryphyllene, -humulene and other sesquiterpenes) Aging of all semi-volatile organic carbons (SVOCs) added Included processes:SOA species in CMAQ:AORGAJ and AORGAI

AORGBJ and AORGBIAORGBISJ and AORGBISIAORGBSQJ and AORGBSQI

AORGAGJ and AORGAGI

Simulated Secondary Organic Contributions From MonoterpeneFrom Isoprene From Antropogenic VOCs From Aged SVOCs Compare to Primary From Sesquiterpene

PM2.5 performance improves

before and after OC performance

Summary2007 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 impactsPerformance 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 worseSOA formation is possibly underestimated New SOA module improves the summer PM2.5 forecasts Better emissions estimations for organic PM is critical

AcknowledgementsGeorgia 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.

Performance MetricsForecastObservation

False AlarmsHitsCorrect NoneventsMissedExceedences

Rained a lot in August. Soil moisture wetter than typical. Cooler temperaturesLess A/C use => Less EGU NOx (about 30% of total NOx)Also thundershowers are hard to model. Rained a lot in August. Soil moisture wetter than typical. Cooler temperaturesLess A/C use => Less EGU NOx (about 30% of total NOx)Also thundershowers are hard to model. OC underestimation in June-July-August Cooler temperatures in September

OC underestimation in June-July-August Cooler temperatures in September

OC underestimation in June-July-August Cooler temperatures in September