Two examples are shown in Fig. . The horizontal axis represents the time elapsed from the start of NaCl injection. The upper panel shows the time variation of droplet concentration in a size range 8.5 ∼ 9.4 µ m (droplet diameter), and the lower panel is a similar plot for 12.5 ∼ 13.4 µ m (droplet diameter). The gray line in each panel was obtained by fitting the Cauchy distribution curve. It is recognized that the smaller droplets (upper) arrive at the top sooner than the larger ones (lower). If we define 'the appearance time' as the peak position of the fitted Cauchy curve, the difference in the appearance time for different sizes corresponds to the difference in the growth period for those sizes.