Model analysis of seasonal variations in tropospheric ozone and carbon monoxide over East Asia

Temporal-spatial variations in tropospheric ozone concentrations over East Asia in the period from 1 January 2000 to 31 December 2004 were simulated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the Regional Atmospheric Modeling System (RAMS). The simulated concentrations of ozone and carbon monoxide were compared with ground level observations at two remote sites, Ryori (39.03^oN, 141.82^oE) and Yonagunijima (24.47^oN, 123.02^oE). The comparison shows that the model reproduces their seasonal variation patterns reasonably well, and simulated ozone levels are generally in good agreement with the observed ones, but carbon monoxide concentrations are underestimated. Analysis of horizontal distributions of monthly averaged ozone mixing ratios in the surface layer indicates that ozone concentrations have noticeable differences among the four seasons; they are generally higher in the spring and summer while lower in the winter, reflecting the seasonal variation of solar intensity and photochemical activity and the fact that the monsoons over East Asia are playing an important role in ozone distributions.