A Numerical Simulation of Local Winds and Photochemical Air Pollution (II): Application to the Kanto Plain

Abstract

The two-stage numerical model developed by Kimura (1983) is extended to three-dimen-sional and used to study the relation between local winds and photochemical air pollution on the Kanto Plain. The first stage is a three-dimensional, timedependent local winds model which gives the wind velocity and vertical diffusion coefficient. The second stage is a photochemical air pollution model which uses the results of the first stage as input data.
The calculated results are compared with observed surface wind velocity and pollutant concentrations when the large scale wind are light (≤3m/s). Good agreement between calculated and observed wind fields is obtained. The calculated concentration of ozone also agrees with the observed oxidant concentration, which is expected to be almost equal to ozone concentration. The simulation also suggests that the mountainous area of Central Japan is very important for the wind system over the Kanto Plain, forcing pollutants from the Tokyo metropolitan area to be more often transported westward than eastward.
Previous air pollution models have needed a lot of meteorological data but some of these, such as upper level wind velocities, are difficult and expensive to obtain. The two stage model will be very useful for preliminary estimation of photochemical air pollution effects where detailed meteorological data are not available.