Abstract:

Long range transport of 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 paper represents the first study simulated the regional scale distribution of tropospheric ozone over the Continental South East Asia Region (CSEA) of Thailand, Myanmar, Cambodia, Lao and Vietnam. The Models-3 Community Multi-scale Air Quality (CMAQ) modeling system, driven by the NCAR/Penn State Fifth-Generation Mesoscale Model (MM5), is used for the purpose. Two historical episodes of January 26-29, 2004 (Jan episode) and March 24-26, 2004 (March episode) were selected which represent the typical meteorological conditions for high hourly ozone concentrations, above 100 ppb, in the region during a year. The episode analysis was made based on available data from 20 and 3 monitoring stations located in Thailand and Ho Chi Minh City (HCMC) of Vietnam, respectively. The episodes were characterized with hourly ozone levels above the National Ambient Air Quality Standards of Thailand and Vietnam of 100 ppb at a number of the monitoring stations. The maximum ground level concentrations of ozone for January 2004 and March 2004 episodes reached 151 ppb and 173 ppb, respectively, in the urban plume of the Bangkok Metropolitan Region (BMR). The simulations were performed with 0.5o × 0.5o emission input data which was prepared from the regional anthropogenic emission inventory used in the Transport and Chemical Evolution over the Pacific (TRACE-P), and the biogenic emissions obtained from the Global Emissions Inventory Activity (GEIA). The simulated overall picture of ground level ozone concentrations over CSEA domain shows that the concentrations were high at the downwind areas at a considerable distance from large urban areas such as BMR and HCMC. During the Jan episode the ozone plume moved southwestward following the Northeasterly monsoon while during the March episode the ozone plume moved northeastward following the Southwesterly monsoon. The model performance was evaluated on the available observed hourly ozone concentrations. The model system was shown to be able to reproduce the peak ozone levels that occurred during the episodes at these two large urban areas, and capture the day by day variations during the selected episodes. The performance statistics MNBE, NGE, and UPA for the simulated ozone concentrations are within U.S. EPA guidance criteria and are comparable to those reported previous for other regional ozone simulations. It is shown that the MM5/CMAQ system is the suitable modeling tools for ozone prediction over the CSEA.

Presentation: http://www.cleanairnet.org/baq2006/1757/docs/SW4_5.ppt

Full paper:

Regional-Scale Modeling Ozone Air Quality Over the Continental South East Asia During Selected Episodes [.doc, 770Kb]