The impact of topography and urban building parameterization on the photochemical ozone concentration of Seoul, Korea

Several numerical experiments have been undertaken in order to clarify the impacts of detailed topography and building parameterization on meteorological and photochemical environments. In this study, we carried out a comparative examination on the meteorological fields of topographies that had different resolutions and building information. By analyzing practical urban ground conditions, we revealed that there were large differences in the ozone concentration for each run. The MM5-CMAQ model was used to assess the ozone differences in each case, during the episode day in Seoul, Korea. Meteorological conditions estimated by MM5 command a great influence on the dispersion of air pollutants in complex areas. The reasonable feature of topography that has a high resolution induces a steeper slope in comparison with that of a topography that has a low resolution. Therefore, there is a difference in orographic forcing between the two sets of simulations. This causes a difference in the estimated ozone concentration. A higher ozone concentration tends to be forecasted when using topography data that have a high resolution with an appropriate limitation to the mixing height and the nocturnal boundary layer. The urban buildings parameterization scheme is also strongly associated with the estimation of meteorological and photochemical fields. The length of homogeneous roughness in an urban area corresponds to observations in all other parameterizations of urban buildings in this study.