Research Article
Impacts of Chemical and Synoptic Processes on Summer Tropospheric Ozone Trend in North China
Figure 4
The spatial distribution of HCHO in summer (JJA) is from 2005 to 2016 (units: 1018 molec·cm−2). (a) 2005, (b) 2006, (c) 2007, (d) 2008, (e) 2009, (f) 2010, (g) 2011, (h) 2012, (i) 2013, (j) 2014, (k) 2015, and (l) 2016.