Understanding the Impact of Meteorology on Ozone in 334 Cities of China

Ozone (O₃) is one of the major pollutants in China, and it depends on the meteorological condition. In this study, we analyzed the characteristics of O₃ pollution and the complicated interactions among the meteorological factors, which had strong effect on generating O₃. The results showed that O₃ pollution was becoming serious and the high-value area expanded significantly in 334 cities of China from 2015 to 2017. Based on Generalized Additive Models (GAMs), it was found that O₃ was influenced by air pressure, temperature, relative humidity, wind speed, wind direction, sunshine duration, evaporation and precipitation. Different cities were influenced by different meteorological combinations, and the Top 3 influence factors in the 334 cities are temperature (90.77%), relative humidity (68.15%) and sunshine hours (66.96%). In addition, we also found that the influence of these meteorological factors on O₃ pollution was non-linear, and was affected by cross-factors and time variable. The GAMs were further used to identify the dominant meteorological factors in each city and to forecast the O₃ concentration. If only the time variables, the non-linear relationship among the meteorological factors and O₃ were considered, the average R² of GAMs was 0.64±0.16. However, comprehensively considering the time variable, the non-linear effects, and interactions, the average R² of revised GAMs increased to 0.72±0.15 (i.e. the improvement ratio of the GAMs were 13.22% ±16.40%, and the R² was significantly improved in 96.72% of cities after considering the interactions among the meteorological factors in the GAMs based on 10-fold cross-validation method). The results showed that the GAMs could predict O₃ concentration accurately from 2015 to 2017.