REGIONALSCALE MODELING OZONE AIR QUALITY OVER THE CONTINENTAL SOUTH EAST ASIA DURING SELECTED EPISOD

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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

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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/CMAQ for 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.

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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
AQM stations in HCMC
CSEA domain 40 cells x 40 cells
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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.

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MM5/CMAQ MODEL SYSTEM
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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.

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SELECTION OF OZONE EPISODES (1)
26-29 January 2004
24-26 Mar 2004
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SELECTION OF OZONE EPISODES
Episode 1 Jan 26 to 29, 2004 Episode 2 Mar 24
to 26, 2004
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WIND FIELDS GENERATED FROM MM5
Modeled wind fields in the lowest layer at 600
UTC on (a) 26 January 2004 and (b) 24 March
2004.
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MODELING PERFORMANCE
Statistical parameters for model evaluation
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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)



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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
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Modeled surface ozone distributions over CSEA
domain Jan 2004 Episode
1400 LST 26 Jan, 2004
1400 LST 27 Jan, 2004
1400 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.

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Modeled surface ozone distributions over CSEA
domain Mar 2004 Episode
1400 LST 24 Mar, 2004
1400 LST 25 Mar, 2004
1400 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.

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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.