Seasonal analysis of large-scale heavy precipitation events in Bulgaria

Climate in Bulgaria became not only warmer but also drier at the end of the 20th century. During the last decade however, precipitation totals have increased mainly due to the contribution of heavy rainfall events which caused severe floods and damages in various economic sectors. In this study a seasonal analysis of heavy precipitation events which is registered during the same process in at least 4 districts in Bulgaria is carried out. All data for extreme precipitation (totals ≥60 mm/24 h) from the meteorological network of the National Institute of Meteorology and Hydrology for the period 1991–2017 are used. An increase of the annual number of days with heavy precipitation is found for the investigated period. About 78% of all days are during the summer and autumn. The classification of synoptic situations connected with 122 days of large-scale heavy precipitation events is also presented for each season. They are divided in different synoptic circulation types, taking into account pressure fields at 500 hPa and sea level pressure. For summer and autumn 4 main combinations of circulation types are defined, which present about 65% of all determined types for each season. The brief analysis shows that more than 80% of all observed cases are connected with varying degrees of damage and even human casualties.