Fig. 6.
Distributions of surface PM2.5 concentrations (color contours) and 10 m wind vectors 24-h, 12-h before and during type I of PM2.5 pollution periods (P1:a,d,g; P5:b,e,h; P6: c,f,i) and the 24-h backward trajectory of air particles at different heights in XY (P1:j; P5: k; P6:l). The insert figures in j, k,l 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.