Impacts of Chemical and Synoptic Processes on Summer Tropospheric Ozone Trend in North China

Figure 2

Monthly average tropospheric O₃ vertical column density (VCD) (units: DU) during 2005–2016: (a) January; (b) February; (c) March; (d) April; (e) May; (f) June; (g) July; (h) August; (i) September; (j) October; (k) November; (l) December; (m) summer time O₃ series in the NCP, indicated as the area in the outer box in Figure 1. The gray shaded area indicates the variation range because the annual summer data cover 3 months (June to August), and the red line is the summer average of the year.