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By Le Hoang Nghiem and Nguyen Thi Kim Oanh Asian Institute of Technology (AIT), Thailand

REGIONAL-SCALE MODELING OZONE AIR QUALITY OVER THE CONTINENTAL SOUTH EAST ASIA DURING SELECTED EPISODES. By Le Hoang Nghiem and Nguyen Thi Kim Oanh Asian Institute of Technology (AIT), Thailand. INTRODUCTION.

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By Le Hoang Nghiem and Nguyen Thi Kim Oanh Asian Institute of Technology (AIT), Thailand

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  1. REGIONAL-SCALE MODELING OZONE AIR QUALITY OVER THE CONTINENTAL SOUTH EAST ASIA DURING SELECTED EPISODES By Le Hoang Nghiem and Nguyen Thi Kim Oanh Asian Institute of Technology (AIT), Thailand

  2. INTRODUCTION • Long rang transport of troposphere ozone and its precursors can significantly impact the air quality in downwind regions. • The problem of regional transport of ozone has been studied for more than three decades in Europe and U.S but not yet in Southeast Asia. • This presentation focuses on: • Application of a photochemical model system MM5/CMAQfor simulating ozone concentrations over the Continental South East Asia Region (CSEA)of Thailand, Burma, Cambodia, Lao and Vietnam in order to understand the transport and distribution of troposphere ozone in the region; and • Evaluate performance of the MM5/CMAQ model system in two urban areas – Bangkok Metropolitan Region (BMR) and Ho Chi Minh City (HCMC),during two historical ozone episodes.

  3. CMAQ MODELING DOMAIN 1. The Continental Southeast Asian region (CSEA): Thailand, Laos, Cambodia, Vietnam, and Burma (5oN-25oN latitude and 91oE-111oE longitude) AQM stations in BMR CSEA domain: 40 cells x 40 cells AQM stations in HCMC

  4. THE MM5-CMAQ MODEL SYSTEM • The Fifth-Generation Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Mesoscale Meteorological Model (MM5) has been used to generate meteorological data. • The photochemical model, The Models-3 Community Multiscale Air Quality (CMAQ) developed by U.S. EPA have been selected to simulation of ground level ozone concentrations.

  5. MM5/CMAQ MODEL SYSTEM

  6. EMISSION INPUT DATA FOR CMAQ • This study used annual 0.5deg x 0.5deg anthropogenic emission inventory from the Center for Global and Regional Environmental Research (CGRER) at the University of Iowa. • Natural hydrocarbon (biogenic) emissions from the global emissions inventory activity (GEIA) 1deg x 1deg monthly global inventory. • The 0.5deg x 0.5deg biogenic emissions were prepared by interpolation of the 1deg x 1deg biogenic emission. • The emissions have to prepare in hourly emission for CMAQ ready format.

  7. SELECTION OF OZONE EPISODES (1) 26-29 January 2004 24-26 Mar 2004

  8. SELECTION OF OZONE EPISODES Episode 1: Jan 26 to 29, 2004Episode 2: Mar 24 to 26, 2004

  9. WIND FIELDS GENERATED FROM MM5 Modeled wind fields in the lowest layer at 6:00 UTC on (a) 26 January 2004 and (b) 24 March 2004.

  10. MODELING PERFORMANCE Statistical parameters for model evaluation

  11. 160 2 R = 0 . 89 140 120 100 Modeled (ppbv) 80 60 40 20 0 0 20 40 60 80 100 120 140 160 Measured (ppbv) Comparison of hourly average ozone concentrations between modeled and observed concentrations at (a) EBMR, (b) WBMR and (c) HCMC for 26 to 29 Jan 2004 episode EBMR WBMR HCMC Scatter plots of measured ozone concentrations vs. modeled values (a)

  12. 180 160 140 120 2 R = 0 . 87 100 Modeled (ppbv) 80 60 40 20 0 0 20 40 60 80 100 120 140 160 180 Measured (ppbv) Comparison of hourly average ozone concentrations between modeled and observed concentrations at (a) EBMR, (b) WBMR and (c) HCMC for 24 to 26 March 2004 episode EBMR WBMR HCMC Scatter plots of measured ozone concentrations vs. modeled values

  13. Modeled surface ozone distributions over CSEA domain– Jan 2004 Episode 14:00 LST 26 Jan, 2004 14:00 LST 27 Jan, 2004 14:00 LST 28 Jan, 2004 • Elevated ozone concentrations are found in the southwestern BMR and the southwest of HCMC. • The ozone plume moved southwestward following the Northeasterly monsoon • The width of the modeled plume with the ozone concentration above 100 ppb in BMR was 50-80 km while for HCMC the width of the 50ppb isopleth was about 30-50$ km.

  14. Modeled surface ozone distributions over CSEA domain– Mar 2004 Episode 14:00 LST 24 Mar, 2004 14:00 LST 25 Mar, 2004 14:00 LST 26 Mar, 2004 • The ozone plume moved northeastward following the Southwesterly monsoon and the maximum width of the modeled plume with the ozone above 100 ppb was about 70 km from BMR. • For HCMC the ozone plume moved northward and the concentration in the city plume was lower with the width of isopleth of 50ppb around 40 km. • This implies that long-range transport of ozone may cause elevated concentrations in remote area downwind of polluted regions.

  15. SUMMARY AND CONCLUSION • The MM5/CMAQ model system performed reasonably well for two selected O3 episodes over the Continental South East Asia Region. • The performance of CMAQ is satisfactory in terms of performance statistics. • The diurnal variation and spatial distribution of O3 concentrations that followed the wind fields. • The modeled O3 concentrations were high at a considerable downwind distance from big urban area such as BMR and HCMC. • Effects of ozone long-range transported from urban areas to surrounding areas and subsequent damage to the agricultural crops and forestry should be further assessed using the evaluated modeling system.

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