Evaluation of summertime surface ozone in Kanto area of Japan using a semi-regional model and observation

Abstract

Surface ozone is an air pollutant and harmful to human life. The spatial distribution of the air pollution has been estimated by chemical transport models, but still there are large uncertainties depending on detailed condition of the region. In this study, we extended Goto et al. (2015a) for implementing a chemical transport model to simulate short-lived gases such as ozone over Kanto area (around Tokyo in Japan) for August 2010. Comparison of simulation results with observed data indicated that the model had ability to capture observed ozone diurnal cycles over the target region with high correlation coefficients (0.69–0.81). The simulation result showed a vital role of meteorological conditions in the model performance. The correlation coefficients were much higher (0.78–0.87) and biases were lower (<35%) when the meteorological conditions were stable. In contrast, dominance of local pressure system and an associated complex wind field were main reasons for overestimated surface ozone concentrations in the unstable weather conditions.This study helped achieve a better understanding of the chemistry transport model performance under unstable meteorological conditions in the Kanto area. Maximal association between meteorological factors and surface ozone distribution was revealed. In addition, uncertainty of emission inventories of ozone precursors especially the underestimate NOx level certainly contributed to high level surface ozone during nighttime in this study.