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Introduction

An Evaluation of the Influence of the Morning Residual Layer on Afternoon Ozone Concentrations in Houston Using Ozonesonde Data. Introduction. The Houston-Galveston-Brazoria area (HGBR) is noted for its violations of EPA NAAQS

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Introduction

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Presentation Transcript

  1. An Evaluation of the Influence of the Morning Residual Layer on Afternoon Ozone Concentrations in Houston Using Ozonesonde Data

  2. Introduction • The Houston-Galveston-Brazoria area (HGBR) is noted for its violations of EPA NAAQS • > 220 Ozonesondes were launched during Houston, TX as part of TexAQS II and IONS-06 • Where do polluted airmasses come from • What effect do local meteorological conditions have on air quality • Where will polluted air travel after leaving HGBR

  3. HGBR Area Map

  4. Boundary Layer Evolution • Convective (daytime) and stable (nighttime)

  5. Boundary Layer Characteristics • The Nocturnal Boundary Layer: • Stable (upward heat flux) • Shallow (100s of meters) • Residual layer (RL) above NBL • RL height – Identified by capping inversion and RH decrease. • RL often retains characteristics of previous day’s mixing layer

  6. Boundary Layer Characteristics • Convective Boundary Layer • Unstable • Typically 1000s of meters • Has a large “mixed layer” • Mixed layer height - 4 ways to find it

  7. Boundary Layer Pollution Effects • RL can act as trace gas “reservoir” • “reservoir” effect depends on (shear) turbulence eddies can cause mixing. • Land and sea breeze

  8. Case Study 1 • 4-5 Aug. 2004

  9. Case Study 1 • HYSPLIT results • 1.25 km air remained in study area over 4-5 aug • Some questions

  10. Case Study 2 • 1-2 Sept 2006 • Occurs after a cold front • Background Effect

  11. Case Study 2 • Land/Sea breeze

  12. Case Study 3 • 5 Oct 2006 • 8 hr mean (oct 4) 52.6 ppbv • 1.4-1.8 km interaction With LFT.

  13. Case Study 4 • 10-11 Aug 2007 • Light winds • Why no intensification • Imported O3 and LFT interactions

  14. Mean Profiles • Calculating mean O3 production • PM profile enhancements = LFT interaction

  15. Residual Layer • Fairly High Correlation • Slightly less max AM O3 than the day before • Removal of several outliers due to changing synoptic conditions leads to higher correlation

  16. Residual Layer and Afternoon O3 concentration • Compare RL ozone to afternoon ozone • Compare Previous day 8 hr average to afternoon ozone

  17. END

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