[Impact of Meteorological Factors on Ozone Concentration in Four Typical Cities of Guangdong Based on Generalized Additive Model].

Based on the observation and reanalysis data in Guangdong from 2015 to 2020, the variation characteristics of ozone （O₃） concentration in Guangdong and four typical cities were analyzed, and the effects of meteorological factors on O₃ concentration in different cities and different seasons were revealed based on the generalized additive model （GAM）. The daily maximum 8-hour average O₃ concentration （O₃_8h） increased significantly from 2015 to 2019, with a trend of 5.0 μg·m^-3·a^-1, and decreased slightly in 2020 in Guangdong. The O₃_8h concentration and the total number of polluted days were substantially higher in autumn than those in other seasons in Guangdong and showed different variation characteristics in four typical cities. The highest values in Guangzhou, Heyuan, Jieyang, and Maoming occurred in summer and autumn, spring and summer, spring and autumn, and autumn, respectively. The regression model had a good fit for the variation in O₃_8h concentration, and the seasonal models were generally better than the annual models. As for the seasonal models, the average R² values were 0.78, 0.69, 0.70, and 0.65, and the mean interpretation rate of variance （IRV） values were 79%, 71%, 73%, and 67% in Guangzhou, Heyuan, Jieyang, and Maoming, respectively. The equation fitting degrees of the optimal models varied considerably in different cities and different seasons, with the R² values ranging from 0.52 to 0.83 and the IRV values ranging from 55.5% to 86.9%. The O₃_8h concentration showed a nonlinear relationship with meteorological factors. The meteorological factors that had a significant impact on the variation of O₃_8h concentration in different cities and seasons differed considerably, and all of the meteorological factors were in the top three lists of importance. Relative humidity was the most important meteorological factor affecting the variation in O₃_8h concentration in different cities, followed by the V-component of wind. When the relative humidity was below 45%, the O₃_8h concentration was relatively higher. When the relative humidity was above 45%, the O₃_8h concentration decreased with the increase in relative humidity. Higher O₃ concentrations appeared when the wind speed was greater than 2 m·s^-1, indicating the regional transport of pollutants and emphasizing the importance of regional joint prevention and control.