Ho Chi Minh City (HCMC), the largest city of Vietnam and the seventh city with the highest density of inhabitants in the world (3,300 persons by kilometer square) (HCMC Urban Drainage Company, 1998), is one of the cities in the world which are seriously influenced by pollution. The main sources of atmospheric pollution are vehicles (motorbikes), the industry and population. | TẠP CHÍ PHÁT TRIỂN KH CN TẬP 9 SÓ 5 -2006 AIR QUALITY MESO-SCALE MODELING IN HO CHI MINH CITY EVALUATION OF SOME STRATEGIES EFFICIENCY TO REDUCE POLLUTION Quoc Bang Ho 1 Alain Clappier 2 Erika Zarate 2 Hubert van den Bergh 2 1 Institute for Environment and Resources IER VNU-HCM 2 Air and Soil Pollution Laboratory Swiss Federal Institute of Technology Switzerland Manuscript Received on November 29th 2005 Manuscript Revised May 12th 2006 ABSTRACT Ho Chi Minh City HCMC the largest city of Vietnam and the seventh city with the highest density of inhabitants in the world 3 300 persons by kilometer square HCMC Urban Drainage Company 1998 is one of the cities in the world which are seriously influenced by pollution. The main sources of atmospheric pollution are vehicles motorbikes the industry and population. Numerical models are the only existing tools able to predict air quality concentrations and to determine the strategies of reduction of air pollution in HCMC different scenarios were tested. The results obtained show that the wind direction is more influenced by global scale than local phenomena. The results of the simulations show that the ozone plume is 90km in length and 30 km in width at 12h00 LT. During the selected episode 8 1 2003 the zone in the SouthWest of HCMC is the most polluted one 180ppb at midday . 1. INTRODUCTION The economic growth and urbanization in Ho Chi Minh City HCMC of Viet Nam have caused air pollution episodes of high ozone O3 . The main sources of atmospheric pollution are vehicles motorbikes the industry and population. In the busy streets of HCMC 2 305 415 motorcycles and 332 622 cars were counted at the end of 2003 for a population of 5 625 million people in an area of 2 kilometer square. According to the HCMC s General Statistics Office there are about 28 500 factories in the city distributed in ten industrial zones and two exports processing zones producing a total of 60 128 tons per year of SO2 15 295 tons per year of NO2 and 1