A nationwide 3D spatio-temporal homogeneous radar composite for Germany has been created using 16 single-polarization C-band radars, covering now a period of 20 years. This dataset enables a detailed analysis of hail statistics, including regional differences, as well as preliminary estimates of long-term changes and emerging trends.The TRACE3D tracking algorithm for severe convective cells with potential hail signals (> 55 dBz) was used to identify 13,324 potential hail tracks (PHTs) during the summer half-year (2005 – 2024). The spatial distribution of these PHTs reveals distinct regional patterns, including a north-south gradient influenced by the proximity of northern Germany to the North Atlantic and by orographic features. The highest hail frequency occurs south of Stuttgart, in the Neckar Valley, over the Swabian Jura, and over the foothills of the Alps. Most tracks are shorter than 45 km and last less than 75 minutes (both 75th percentile). Around 50% of the tracks follow a flow direction between south and west, aligning with typical mid-tropospheric conditions that favor convection. Furthermore, half of the days with PHTs are associated with atmospheric blocking regimes, such as Scandinavian, European, and Greenland blocking.Temporally, hail events in Germany are unevenly distributed, with 63 % of days recording no PHTs and only infrequent periods of intense hail activity with many tracks on a day. Although many hail days usually tend to be isolated (~ 43 %), clustering of hail days can occur under specific synoptic conditions; however, such sequences rarely extend beyond two weeks.Trend analyses reveal a high annual variability in the number of PHTs, with no clear nationwide trend over the past 20 years. However, significant regional differences emerge: In northern and central Germany, there are generally no statistically significant trends, although a slight downward tendency can be observed. In contrast, southern Germany exhibits a significant increase in the number of days with PHTs.
Mohr et al. (Fri,) studied this question.