Numerical simulation of the springtime trans-boundary air pollution in East Asia

Abstract

During the spring, the high concentrations of ozone (O3) and aerosols are frequently observed aloft in Japan. Such episodes supposedly are caused by the trans-boundary air pollution from other parts of East Asia. To confirm this hypothesis, an episode during the month of April 1993 is investigated by numerical simulations for East Asia with a regional meteorological model and a chemical transport model; the model can reproduce some of the key features of ozone and sulfate (SO4 2−) aerosol concentration,s specifically, the time variations in ozone concentrations measured at several remote sites located in Japan and the day-to-day variations and vertical profiles for sulfate aerosol concentrations observed in Osaka. Model simulations show that (1) air pollutants such as sulfate aerosol, nitrate (NO3 −) aerosol, and ozone are transported from the Asian continent to the Japanese Islands under synoptic meteorological conditions; (2) the trans-boundary pollutants increase urban air pollution in Japan; and (3) in the future, the air quality in Japan will be greatly impacted by increasing emissions in developing Asia.