The aim of this study is to elucidate the relationship between the formation of photochemical oxidants (Ox) and the emission rate of the primary pollutants in the Osaka bay area. In this first report, a three-dimensional air quality model OASIS was presented, and its accuracy was verified over the typical summer time for the pollutant (NO, NO
2, O
3) concentrations in three unique areas, Harima 36km×28km, Hanshin 32km×32km, and Osaka 28km×36km, which are located in the Osaka Bay and surrounding areas (180km×180km×5km) . In order to represent the regional and seasonal characteristics of air pollution, the calculation results were compared to the spatially averaged data of 37 typical summer days with remarkable Ox generation (daily precipitation=0.0mm day, daily maximum temperature≥35°C, daily maximum radiation≥3.0MJ/m
2/h, daily average wind speeds≤4.0m/s, weak general wind) selected from those data in August in 1991-1995, 155 days in total, observed at 106 ambient air pollution monitoring stations in Osaka and Hyogo. The verification was evaluated by the property for reproducing current status recommended by US EPA for photochemical oxidants with the index of agreement for wind vectors. As a result, it was shown that OASIS has sufficient accuracy for reproducing air pollution conditions of a typical summer day in the Osaka bay and surrounding areas.
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