| Satellite and surface observed O3 concentrations were applied to analyze the spatial-temporal distribution and trends of O3 over China. The satellite and surface observations agree well, revealing that the highest concentrations of O3 are distributed in East China, and with a seasonal pattern of high in summer and low in winter. Records of the diurnal variation of O3 over the four cities of interest (Beijing, Shanghai, Guangzhou, and Chengdu) reveal that O3 peaked at 15:00-16:00 each day. Statistical analysis indicates that there is no significant difference in O3 concentration between weekends and weekdays for the cities of Beijing, Guangzhou, and Chengdu. Surface O3 over China increased dramatically from April 2013 to June 2018. The increase of the surface O3 concentration from 2014 to 2017 is significant for Beijing, Shanghai, and Chengdu, and the rates of increase were 2.36, 3.3, and 3.6 μg·(m3·a)-1, respectively. Analysis based on the daily max 8 h rolling mean O3 concentration reveals that the percentage of days with O3 concentration exceeding the national standard (160 μg·m-3) in 2014-2017 were 17.2% for Beijing, 10.7% for Shanghai, 8.8% for Guangzhou, and 11.2% for Chengdu. O3 pollution is most severe in Beijing where the highest O3 concentration occurs, along with the largest number of days with daily max 8 h rolling O3 concentration exceeding 160 μg·m-3. |
