Modeling Compliance with the 8-Hour Standard

Jay Olaguer

Houston Advanced Research Center

10/06/04

Texas Environmental Research Consortium

• TERC is a consortium of stakeholders:– Local government agencies (City of Houston, HGB

and DFW counties)– Environmentalists (ED, GHASP)– Business and Industry (GHP, Dallas C of C).

• TERC’s mission:– Fund research to improve ozone science and air

modeling in East Texas– $5 million from TX Legislature for 2004-2005– Collaboration with TCEQ in identifying research

Basic Problem

• How to model attainment of 8-hr standard?

• Transport yields background up to 80 ppb

• Current AQ models used for SIPs are barely sufficient for 1-hr, let alone 8-hr

• Selection of appropriate episode(s) not straightforward (Full ozone season?)

• Need much more observational data to evaluate model performance

Meteorology

1-hr Standard 8-hr Standard

Boundary Layer Free Troposphere

(0-3 km) (3-16 km)

Horizontal Flow Vertical Motion

Transport

1-hr Standard 8-hr Standard

Daytime Night-time

Urban-to-Regional Regional-to-Continental

Chemistry

1-hr Standard 8-hr StandardHighly Reactive Moderately Reactive VOCs (e.g., ethylene) VOCs (e.g., n-butane)Rapid Ozone Long-Lived Products Formation (e.g., PAN, acetone)

8-Hr Conceptual Model

• Explain high background ozone in E. TX

• Explain local 8-hour exceedances in: HGBPA, DFW, NE TX EAC areas.

• Information sources: surface monitors, previous conceptual models, trajectory analyses, forecast modeling (NCAR)

• Statistical and physical model analysis to get a mental picture of causal mechanism

Transport from Out-of-State

• Examine transport impact of out-of-state sources on E. Texas regions

• Apportion source region/type contributions for various meteorological episodes:– Aug 1999 DFW episode– Sep 1999 Austin/San Antonio episode– Aug/Sep 2000 HGB episode

• Sensitivity to height of air column in model

Best Practice for Modeling 8-Hr Ozone in Context of TexAQS II

• Real-time trajectory and grid modeling for forecasting/adaptive observation planning

• Testing of modeling innovations: – Observational data assimilation – Expanded chemical mechanism– Source attribution methods

• Development of regional model for 8-hour SIP applications

Summer 2005 Tetroon Campaign

• Constant altitude balloons to track air flow

• Tower and/or chase aircraft chemical measurements (ozone, VOCs, NOy)

• Research Focus:– Nocturnal meteorology and transport– Nocturnal chemistry– Export of pollution from Houston to E. Texas

Summary

• Meteorology– Conceptual model development– Testing model innovations during TexAQS II

• Transport– Regional modeling and source apportionment– Tetroon campaign to track regional air flow

• Chemistry– Chemical measurements on tower/aircraft– Expanded model chemical mechanism