**5. Conclusions**

We investigated 38 days of thunderstorms when lightning discharges were detected in the vicinity of the Milešovka observatory; the site of a vertically-oriented Ka-band cloud radar. We analyzed vertical profiles of diverse cloud radar-derived quantities to find differences between characteristics when a lightning discharge was recorded close to the radar site (≤1 km, NL) and characteristics when a lightning discharge was observed from 10-20 km from the radar site, i.e., there was a non-thunderstorm cloud above the radar (FL).

We concentrated on hydrometeor distribution, values of LDR and vertical air velocities (AV). We are aware that in most cases, we worked with data that were not directly measured; instead, we derived them (hydrometeor species, AV). The way we processed the data and derived the variables may have affected our results. Nevertheless, we believe that the procedure we chose can contribute to the current knowledge and/or the confirmation of the current knowledge on the occurrence of lightning in the atmosphere.

We showed that our technique of classifying hydrometeors provides outputs that reasonably describe thundercloud structures. Since the classification essentially depends on derived AV, our results indirectly prove that the way we derive AV provides acceptable results, although we cannot confirm it exactly.

The analysis of data characteristics of NL as compared to FL showed that:

• In the case of NL, the vertical profiles contain vertically-oriented areas with clearly high LDR, likely caused by an intensified electric field, which makes the ice particles align. The areas

with increased LDR are visible at an elevation from 4 to 6.5 km above the radar, approximately. This finding confirms results published in other studies. Unlike other studies, which usually analyze one single event, we processed 38 days of thunderstorms.

• The vertically-oriented areas with increased LDR comprise various hydrometeors, namely the ice and snow particles, graupel, hail, and (supercooled) cloud water. These are the areas which meet the condition for the development of electrification by the collision of hydrometeors. In our opinion, electric field formation due to the collisions of graupel and ice particles is followed by the alignment of ice particles in the electric field and both the processes contribute to increases in LDR.

**Author Contributions:** Z.S. and J.M. conceived the paper and interpreted the results. Z.S. developed the presented algorithms, applied them, and partly wrote the manuscript. J.M. conducted analyses, graphically processed results, and wrote most of the manuscript. O.F. helped in radar data processing and interpretation of the results. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by project CRREAT (reg. number: CZ.02.1.01/0.0/0.0/15\_003/0000481) call number 02\_15\_003 of the Operational Programme Research, Development, and Education. It was also supported by Charles University (UNCE/HUM 018) and by project Strategy AV21, Water for Life.

**Acknowledgments:** We are very much thankful to Petr Pešice, who helped us in collecting and administrating cloud profiler data from the Milešovka observatory. We also owe great thanks to BLIDS for providing us with lightning data as well as the Czech Hydrometeorological Institute who has delivered us the C-band weather radar data. Moreover, we acknowledge Herman Russchenberg and Christine Unal from Technical University Delft, who were of particular help in basic radar data processing.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study, in the collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.
