*2.5. Methods of Comparison between Cloud Radar Data and Lightning Data*

The comparison of cloud radar data with lightning data is not straightforward due to differences in their location. The cloud radar is a profiler, i.e., it registers a vertical profile from a particular location on the ground, whereas lightning data can be registered anywhere. Thus, in this study, we reduced the lightning dataset to lightning discharges that were located within a circular area around the Milešovka observatory, where the Milešovka observatory was situated in its centre. We considered several circular areas (with a radius of 1, 2, 3, 5, 7, 10, and 20 km) around the Milešovka observatory.

We decided to divide storms above the radar into storms with lightning (denoted "near lightning", NL) and those without lightning (denoted "far lightning", FL). After several testing, we selected 1 km as the radius defining NL because we believe that this is the distance, which describes the condition of a cloud above the Milešovka observatory, when the development of lightning (i.e., electrification) is taking place or will soon take place over the Milešovka observatory (or its nearest vicinity). Contrary, the FL (lightning registered at a distance of 10-20 km from the observatory) represent the condition of a cloud above the Milešovka observatory, when no discharges were recorded in its direct vicinity. In Section 3, we depict results for NL as compared to FL.

Another issue in comparing cloud radar data with lightning data is the difference in their temporal resolution. Cloud radar data are recorded every 2 s approximately, while lightning data are registered at a temporal resolution in the order of ms. However, this is not of high importance since based on our experience the temporal variability of radar measurements is not very high, even in thunderstorms.

Being aware of the difference in temporal resolutions of radar and lightning data, we still decided to consider cloud radar data registered just before and just after the time of any lightning discharge; i.e., we considered two consecutive cloud radar recordings (distant by 2 s) that we coupled with a lightning discharge. This way, we compared cloud radar data (vertical profiles of Hclass, AV and LDR) with lightning data in circular areas around the Milešovka observatory (NL vs. FL) during the 38 days

of thunderstorms (Table 3). Note that there were 990 lightning discharges observed up to 1 km from the Milešovka observatory during the 38 days of thunderstorms and 171,754 FL discharges.
