Rainfall erosivity is an indicator of the potential of precipitation to generate erosion processes and is essential for understanding the climatic vulnerability of a region. This article aims to develop a model for evaluation the average annual and seasonal rainfall erosivity in areas with different climatic and orographic conditions. The studied area covers the regions of Lovech and Kardzhali, which are characterized with high intensity of erosion processes and high erosion risk. To achieve the goal of the study Precipitation Concentration Indices (PCI) and Modified Fournier Indices (MFI) are calculated based on monthly and annual precipitation totals for the period 1961 – 2020. Extreme precipitation months are determined based on percentile distribution of monthly precipitation data. The threshold for extreme dry months is 10-th percentile and for extreme wet months is 90-th percentile. According to the results of the study investigated areas are described with moderate class of rainfall erosivity for average PCI index and with low erosive class, concerning average MFI index in examined period. Increasing of the extreme precipitation months are established in the period 1991 – 2020 in comparison to 1961 – 1990. This tendency is valid for both extreme wet and extreme dry months. The results of this study can contribute to the creation of appropriate strategies and development of preventive activities, to reduction and possible elimination of the negative impacts of extreme precipitation.

Climate in Bulgaria became not only warmer but also drier at the end of the 20^th 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.

A classification of circulation types for the region of Bulgaria is made on daily basis using subjective (manual) approach, covering 56-year period (1961-2016). The classification is based on mean sea

The atmospheric circulation, not only near the surface but also at high altitudes, is probably the main factor determining the weather and climate of a given area, along with its latitude, altitude, the shape of the relief of the area and its surroundings, and the proximity of water basins of different sizes. The main objective of this study is to investigate the relationship between anticyclonic circulation types in the middle troposphere at the 500 hPa level and the seasonal summer temperature over the region of the central Balkan Peninsula, particularly Bulgaria. A previously compiled classification of atmospheric circulation is used, and the frequencies of the circulation types are correlated with the mean seasonal (monthly) temperature, where the extreme seasons and months are defined as the 10th percentile for cold summer seasons and months and the 90th percentile for warm ones. A positive and statistically significant correlation was found for the anticyclones located southwest of Bulgaria and a negative one for those located southeast of it. A comparison between the last two 30-year climatological periods (1961–1990 and 1991–2020) was also made, and an irrefutable decrease in the number of cold summer seasons from 257 to just 17 was found in the last 30 years, respectively, as well as a rapid increase in the number of extreme warm summer seasons from 26 to 263, encompassing all 15 meteorological stations studied.