Recent Trends in Hail Precipitation for Administrative Districts of Bulgaria

Annual and Seasonal Characteristics of Rainfall Erosivity in the Eastern Rhodopes (Bulgaria)

“…In the cold half-year, precipitation often falls from the warm fronts of cyclones. Thunderstorms develop, with heavy precipitation and sometimes hail, even in winter [35]. Some of the highest maximum daily precipitations in Bulgaria have been measured in this area.…”

“…In winter, especially in recent years, in the studied territory, precipitation is often rain and less often snow, which favours soil erosion by water. Investigating monthly and annual variations in hail events in Bulgaria for the period 1991-2020, Bocheva and Pophristov [35] established a significant increase in hail days in South Bulgaria in the cold half of In winter, especially in recent years, in the studied territory, precipitation is often rain and less often snow, which favours soil erosion by water. Investigating monthly and annual variations in hail events in Bulgaria for the period 1991-2020, Bocheva and Pophristov [35] established a significant increase in hail days in South Bulgaria in the cold half of the year (October-March).…”

“…In Zlatograd, a rainfall of 234 mm/24 h was recorded in October 1970 and 261 mm/24 h in February 1963 [33]. During the summer season, precipitation is of low frequency and, in most cases, is associated with the cold fronts of Atlantic cyclones or the fronts of Azores anticyclones carrying cool oceanic air over the Balkans [35]. Under such conditions, owing to the orography, it is possible for more powerful thunderstorms to develop, with intense precipitation.…”

“…Intense sunlight and high temperatures in summertime dry out Earth's surface, and the soil or rocks easily break down into small particles, which, in a summer storm or in the normal increase in the autumn precipitation, are carried away by the water, and even debris flows can be observed. A high and long-lasting snow cover has not formed in the During the summer season, precipitation is of low frequency and, in most cases, is associated with the cold fronts of Atlantic cyclones or the fronts of Azores anticyclones carrying cool oceanic air over the Balkans [35]. Under such conditions, owing to the orography, it is possible for more powerful thunderstorms to develop, with intense precipitation.…”

“…The increase in the altitude of the studied territory from north to south is not the main reason for the increase in precipitation amounts. The increase in the precipitation is mainly related to the exposure of the slope and the location relative to the mountain ridges on the one hand and the trajectories of Mediterranean cyclones on the other [35]. The average monthly maximum is observed in the cold part of the year (December or January) and has values of 76 and 86 mm in the north part of the study area (at stations in Haskovo and Kardzhali, respectively), 159 mm in January at the station in Tokachka, and 198 mm in December at the station in Kirkovo (in the south part of the region).…”