Fig. 7.
Distributions of surface PM2.5 concentrations (color contours) and 10 m wind vectors during type II of PM2.5 pollution periods (P2:a; P3:b; P4:c) and the 24-hbackward trajectory of particles at different heights in XY (P2:d;P3:e; P4:f). The insert figures in d, e, f refer to the time series of plume particle heights, the lower and higher tentacles, the upper and lower edges of box, and the square and horizontal line in box indicate the minimum and maximum, 25th and 75th percentiles, and mean and median of particle heights, respectively.