*3.1. Data after Quality Control*

In this study, 8184 records are selected as rainfall events, including 7388 stratiform and 796 convective data. The amount of observed mixed-cloud rain is zero. Figure 4 shows the frequency accumulation curve of rainfall intensity recorded. The average *R* of the recorded data is 2.3 mm/h (the calculated average *R* includes only rainy hours, as shown in Section 2.3), and the data with rainfall intensity less than 5 mm/h is more than 90% of the total time of rainfall data.

**Figure 4.** Frequency distribution of rain rates calculated from the whole OTT Parsivel-2 disdrometer datasets.

A division of the rainfall data into different seasons (spring from March to May, Summer from June to August, Autumn from September to November and Winter from December to February) and rainfall types (stratiform and convective rain) acquired by the OTT Parsivel-2 is reported in Table 1. The results shown in Table 1 reflect the trend of precipitation change in this region with different seasons. The frequency of raindrop spectra data recorded in summer is the highest (with 7019 records), followed by autumn (4230 records), spring (3387 records) and winter (only 116 records). In spring, summer and autumn, the total time of stratiform rainfall events *Ts* is higher than the total time of convective rainfall events *Tc*, which reflects the precipitation characteristics of semi-arid areas [44]. The percentage of stratiform rain is from small to large summer (85.9%), spring (93.5%) and autumn (95.5%). Winter is not considered when comparing the characteristics of different seasons due to too few liquid precipitation data recorded. The percentage of convective rain, ordered from small to large, is spring (4.5%), autumn (6.5%) and summer (14.1%). In summer the *R* varies most and has the highest standard deviation of 2.8 mm/h. However, the percentage of rainfall time over the seasons is ordered from small to large, are spring (1.4%), autumn (1.7%) and summer (3.0%).

**Table 1.** Disdrometer-measured data of different seasons: total time with recorded data, the percentage of stratiform and convective rain and percentage of different ranges of rainfall intensity; maximum and average rainfall intensity, and standard deviation of rainfall intensity.


\* The rainfall accumulation is not calculated in winter because of the inclusion of solid precipitation (e.g., snow).

Weak and moderate rainfalls (with rainfall intensity satisfying 0.5 < *R* < 5 mm/h) account for the largest proportion of rainfalls in each season, and data satisfying *R* > 5 mm/h in summer is of the highest percentage of total rainfall time in the season (11.3%). The *R*max is 33.7 mm/h in summer, 21.2 mm/h in autumn and 12.6 mm/h in spring. The *R* and *P*total in summer are also the highest (2.6 mm/h and 236.9 mm, respectively), while the difference in *R* between spring (2.0 mm/h) and autumn (2.0 mm/h) is not significant. The difference in *R*<sup>m</sup> between spring (1.9 mm/h) and summer (1.9 mm/h) is not significant.
