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The main goal of the analysis presented in the paper is to contribute to a clearer understanding of climate changes in Bulgaria, assessing the long-term changes in annual characteristics of surface temperature and precipitation in the period 1961-2020 and providing climate projections to the end of the 21st century. During the last decades of the 20th century, a tendency towards warming occurred in Bulgaria. Since the 1990s, only four years have had negative temperature anomalies compared to the reference period 1961-1990. Changes in the precipitation regime are also apparent, with increasing frequency of days with both torrential rainfall and dry, hot weather. The analysis of future climate is focused on the projected changes under the four RCP climate change scenarios for selected ETCCDI climate indices, computed on a yearly basis: absolute maximum temperature (TXx), absolute minimum temperature (TNn), the maximum number of consecutive frost days (CFD), the maximum number of consecutive summer days (CSU), precipitation sum (RR), number of heavy precipitation days (RR10mm) and maximum number of consecutive dry days (CDD). The projected significant warming is manifested in the spatial patterns and temporal evolution of all considered temperature indicators. Despite the predicted decreasing precipitation trend, especially in Southeast Bulgaria, the changes are statistically significant only for scenario RCP8.5. [ABSTRACT FROM AUTHOR]

Many studies confirm a shift to warmer climate in South East Europe. In Bulgaria, warming trends have been registered since the end of the last century, and different scenarios show increased air temperatures in the future. In the face of climate change, it is a challenge to assess its effect on water resources. The aim of the paper is to evaluate the possible impact of climate change on the discharge of two springs from the Lovech Tarnovo karst basin. This study uses the monthly water balance method to compare the future regime with the baseline regime for two karst springs. For calculations, the software WaterbalANce is applied, which is based on the Thornthwaite–Mather method. The monthly time series of temperature and precipitation for simulations are used from the meteostations neighbor to the springs (stations Pleven for Krushuna and Veliko Tarnovo for Musina). For the purposes of this study, monthly water balance calculations are performed for the baseline scenario S00 (1976–2000) and a set of future climate development scenarios Snn. The first index refers to absolute change of temperature, and the second – to relative change of precipitation. The scenarios S10 and S20 mean change only of temperature, +1.5°C and +3.5°C respectively. The S11 and S21 scenarios assume a 10% decrease in precipitation in addition to the corresponding temperature changes. The input data for any scenario other than the baseline scenario are obtained by corresponding changes in the time series of temperature and precipitation. The results of the water balance calculations show the negative impact of the increased temperature (flow reduction for the Musina spring by 13% and 25%, respectively, only for temperature change, +1.5°C and +3.5°C, respectively). An additional 10% reduction in precipitation will lead to a 33% and 44% drop in average discharge, respectively. Similar results are obtained for the flow rate of the Krushuna spring. Overall, these results show the serious negative impact of future climate change on the discharge of the studied springs. [ABSTRACT FROM AUTHOR]

The importance of this study is to underline the fact that the wind energy potential in the western part of the Black Sea basin can be considered significant, while the wave energy is lower in comparison with oceans. However, in winter time when energy consumption in Bulgaria and Romania is high, the wave energy presents the highest values. The aim of this research paper is to draw a comprehensive picture regarding the wave and wind energy near Bulgaria and Romania coastlines. More precisely, six locations were studied. Regarding the geographical location, the studied points are located in the range 42°N to 45.2°N and 27°E to 30°E as follows: three points are near to the Bulgaria’s coastline and the other three close to Romania’s coastline. In this study, the wind conditions were analyzed at 10-meter height. The data for the wind analysis were provided by the Regional Climate Model (RCM) from Euro-Cordex database (EUR-11) and covers three intervals. All intervals cover 30-year of data as follows: Historical dataset (01 January 1976 to 31 December 2005), near future RCP8.5 scenario (01 January 2021 to 31 December 2050) and future RCP8.5 scenario (01 January 2071 to 31 December 2100). The wave analysis was conducted on the same intervals but using data coming from SWAN model. Finally, by analyzing the resulted coming from this joint evaluation it can be concluded that the presented analysis provides a more comprehensive picture regarding the future wind and wave energy resources in the coastal environment of Bulgaria and Romania, compared with historical period. [ABSTRACT FROM AUTHOR]

Significant floods all over the world, including Romania and Bulgaria, have occurred in the last years as result of climate change and extreme meteorological phenomena manifestation. Overland flooding, the most common type of flooding event usually occurs when rivers or streams overflow their banks as a result of heavy rainfalls or fast snowmelt. In European Union, flood defence management is an essential part of the integrated water management and the European Commission Directive 2007/60, regarding the estimation and management of the flood risks, states that all the member countries have to achieve flood risks maps till the end of 2013. Flood hazard maps must be created to help the communities in finding out which are the different flood risk areas and to provide public awareness and useful information to local authorities and decisions makers in case of possible flood events. Flood risk areas should be also identified and delimited for future land use and development. The development of risk maps assumes the existence and access to extensive databases, detailed maps and GIS data depots for most of the necessary information, as well as expensive software (i.e. ArcGIS, MIKE) and skilled experts. Unfortunately, these criteria are not always met. This paper presents an alternative method to prepare preliminary floodplain maps, based on the use of Autodesk products and Open Source software. The purpose of the method is to introduce basic satellite image display and processing techniques using open source software and freely available satellite data to allow floodplain maps development without using expensive software and unaffordable data. The method consists in DTM (Digital Terrain Model) generation, rivers and watershed delineation and hydraulic modelling in order to generate floodplain maps. [ABSTRACT FROM AUTHOR]

Daily precipitation data measured in 38 meteorological stations during all months of the year in the period (1960 - 2009) are sorted looking for consecutive days with precipitation. The used 38 points are approximately uniformly located on the territory of the country (19 in North Bulgaria and 19 in South Bulgaria) and represent in fact the basic (synoptic) stations in the meteorological network of the National Institute of Meteorology and Hydrology. Fifteen cases of extreme number of consecutive days with precipitation (>15 days) are revealed on the territory of the country during the examined 50-years period. These cases represent exceptionally rare events with a great return period and form a relatively small but obtained through a sort of an enormous volume of data sample that is a good basis for an interesting and significant analysis of the examined rare phenomenon. The obtained results concerning the distribution of the revealed extreme cases over territory, during the years, by seasons and months, and according to the precipitation type amount are summarized in the paper together with the common features of the corresponding synoptic situations. The proposed investigation is a part of a greater research aiming to reveal the spatial - temporary regime of the number of consecutive days with precipitation over Bulgaria and the corresponding typical synoptic situations together with the eventual climatic variations of this regime and their relation to the drought events in the country. [ABSTRACT FROM AUTHOR]