*2.4. Analysed Data: Thunderstorms of 2018 and 2019*

In this study, we used data of the cloud radar situated at the Milešovka observatory (Figure 1) such as Z, LDR, derived AV (Section 2.2) and classified hydrometeor species (Section 2.3) during days with lightning registered up to 20 km from the Milešovka observatory by the EUCLID network. The data covered a period from June 2018 to September 2019. The dataset consisted of 38 days of thunderstorms (Table 3). Continuous data records lasted at least 2 h and more than one thunderstorm could have occurred during a single (analyzed) day.

For the dataset of 38 days of thunderstorms (Table 3), we dispose of ground-based observations of lightning discharges by EUCLID network [35]. We obtained the data from Blitz Informationsdienst von Siemens (BLIDS) [36], which provides it to EUCLID network, for the whole territory of Czechia and its neighborhood. BLIDS uses the time of arrival (TOA) principle to locate lightning discharges. TOA principle is based on assumption that the electromagnetic field induced by a lightning discharge propagates at the speed of light from its origin in all directions. Individual receivers record TOA and the difference in TOA among receivers defines the location of the discharge.

The lightning data include information on geographical coordinates of the discharge (in WGS84), time of the discharge [ms], peak current [kA], polarity of the discharge, type of the discharge (Cloud-to-Ground CG and Cloud-to-Cloud CC), and on quality of data (binary information). The spatial accuracy of the lightning dataset was 0.6 km (median) at a confidence level of 95%, while the lightning detection efficiency was about 100% [37]. All the data used in this study were of good quality according to the binary information in the lightning dataset.

In addition, we obtained weather radar reflectivity factor data at various Constant Altitude Plan Position Indicator (CAPPI) levels for the 38 days of thunderstorms (Table 3) from the Czech radar network (CZRAD; Sokol et al. [38]) operated by the Czech Hydrometeorological Institute. CZRAD network consists of two C-band weather radars recording measurements every 5 min at a horizontal resolution of 1 km. The closest radar is located 100 km southward from the Milešovka observatory. Main product of the two C-band weather radars is the radar-derived rain rate (R [mm/h]), which we calculate using the Z–R relationship, such as Z=200R1.6, where Z is the radar reflectivity factor [mm6/m3] [39]. Furthermore, we had synoptic data from the Milešovka observatory at our disposal, and in this study, we used rain gauge measurements with a temporal resolution of 1 min.


**Table 3.** Date of 38 days of thunderstorms with lightning discharges recorded up to 20 km from the Milešovka observatory in 2018 (left panel) and 2019 (right panel).
