4.2.2. The Distribution of *Dm* and *Nw*

Figure 9a shows the scatterplot of log10 *Nw* vs. *Dm* of the two stations. The maritime convective clusters, continental convective clusters, and the stratiform rain line described in Bringi et al. [41] as well as the convection-stratiform separation line suggested by Thompson et al. [42] are also shown in Figure 9a. The scatter points of two stations show similar boundaries, of which there are both convective rain and stratiform rain types. Meanwhile, there are more points classified as stratiform rain by the classification suggested by Thompson et al. [42], and the averaged log10 *Nw*-*Dm* pairs of two stations are close to the stratiform line described by Bringi et al. [41]. Moreover, for convective rain type, there are more points located at the continental convective cluster rather than maritime cluster for both stations. Compared with the DSD characteristics studied at Yangjiang from July to August by Tang et al. [43], the log10 *Nw* of both two stations are smaller no matter what rain types, suggesting a lower drop concentration of this rain system.

**Figure 8.** Time series of raindrop size distributions (DSD) observed at (**a**) Zhuhai station, (**b**) Huidong station from 00:00 UTC 29 August to 12:00 UTC 31 August. The color density in both (**a**) and (**b**) represents the number concentration in logarithmic units of *N*(*D*)(m−<sup>3</sup> mm<sup>−</sup>1).

**Figure 9.** (**a**) The scatterplots of log10 *Nw* vs. *Dm*; (**b**) probability density functions (PDFs) of *Dm*; (**c**) PDFs of log10 *Nw* at Huidong and Zhuhai stations. Both data are from 00:00 UTC 29 August to 12:00 UTC 31 August. The black dot and pink circle represent Zhuhai data and Huidong data, respectively. The mean values of log10*Nw* and *Dm* are represented by circles (gray for Zhuhai and red for Huidong). The two rectangles correspond to the maritime (cyan) and continental convective (orange) clusters reported by Bringi et al. [41]. The black and purple dash-dot lines represent the characteristics of stratiform rain described in Bringi et al. [41] and the convection/stratiform separation line from Thompson et al. [42], respectively. The square symbols represent the average values of various types of rain, from Tang et al. [43]. CV stands for convective rain, ST is stratiform rain. ZH is short for Zhuhai, and HD is short for Huidong. It is the same in the following figures and tables.

The probability density functions (PDFs) of *Dm* and log10 *Nw* with the mean values are presented in Figure 9b,c. The PDF of *Dm* at Zhuhai station peaks around 1.25 mm while that at Huidong peaks around at 1.75 mm. Additionally, the PDF of log10 *Nw* at Zhuhai station peaks around 3.25 while that at Huidong peaks around at 3.75. This leads to a higher mean value of *Dm* (1.75 mm) and lower mean value of log10 *Nw* (3.18) at Zhuhai station than those at Huidong station. This result indicates that the rain at Zhuhai station has larger drops, but a lower drop number concentration compared to Huidong station.
