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Volume XX |

Ecoclimatic characteristics of the south-western slope of the Pirin Mountains (Bulgaria)

Abstract: The paper characterizes thermal and humidity conditions within one of the insufficiently investigated parts of Bulgaria from the climate point of view, namely the south-western slope of the Pirin Mountains. The initial data for the study (monthly temperatures and precipitation amounts) were obtained from our own meteorological monitoring station for the period 2013-2021, organized by the Department of Climatology, Hydrology and Geomorphology, Sofia University, Bulgaria. By the calculation of Mayr tetratherm (MT), monthly De Martonne aridity index (Im) and Compensated Summer Ombrothermic index (CSOi) the predominance of humid conditions in the studied area is established. There is a large inter-annual variability of the De Martonne aridity index and the Compensated Summer Ombrothermic index, which are more influenced by precipitation than air temperature in the middle part of the mountains. On the other hand, in combination with low precipitation amounts, high temperatures in recent years have contributed to the manifestation of arid features of the climate. The results of the study supplement the insufficient information about the bioclimatic characteristics of the Pirin Mountains and clarify the peculiarities of the climate in these mountains, which have two clearly distinguishable macroslopes with west-southwest and east-northeast exposure.

Volume XIX |

Climate aridity in southern Bulgaria for the period 1961-2015

Abstract: The climate change on a global, regional and local scale is one of the largest problems indicated by the 21st century studies. Some of the major climate changes on the Balkan Peninsula, and in particular in Bulgaria, are related to rising temperatures and decreasing precipitation, which leads to drought and climate aridity. The present study focuses on the investigation of the climate aridity in the non-mountainous part of Southern Bulgaria in order to assess the aridity condition in temporal and spatial scale. The main investigated period is 1961-2015 and the reference periods are 1961-1990 and 1986-2015. The aridity is analysed on the basis of monthly data for air temperatures and precipitation from eight meteorological stations by calculation of De Martonne aridity index and Emberger Index. The survey shows that in all the analysed meteorological stations in Southern Bulgaria there are periods which display characteristics of the semiarid or arid climate. The aridity is well-expressed in the southwest part of Bulgaria (station Sandanski) and the western part of the Thracian lowland (station Plovdiv). Despite the aridity conditions established in the investigated region the tendencies in multiannual variability of De Martonne and Emberger indices show decreasing of aridity during the last 30 years (1986-2015) of the investigated period.

Volume XV |

Volcanic Eruptions in South Europe and the Change of Carbon Dioxide Concentration – Case Study: “Moussala” Basic Environmental Observatory

Abstract: The volcanic eruptions are one of the most characteristic natural sources of CO2 in the atmosphere (IPCC, 1990, 2007). In order to study the effect of volcanic eruptions on the increased levels of CO2, we have used data from the Basic Environmental Observatory (BEO) “Moussala”, Bulgaria, for the period comprised between July 2007 and March 2015. The Carbon dioxide is not a health hazard gas and there is no established limit concentration by the Bulgarian and international law. In this study, we have accepted as extremely high values the values that exceed the 95th percentile of the distribution of the daily average values for the studied period. The days with exceeding CO2 concentration were analysed in terms of volcanic activity (Etna), which could affect the investigated area with the spread of air pollutants and also CO2. The simulations developed by the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) Model are used in order to describe the trajectory and dispersion of pollutant and products from eruptions of Etna in the atmosphere. A synchrony between the occurrence of days with extreme high concentration of CO2 in the atmosphere in the region of BEO “Moussala” and eruptions of Etna volcano was established in most of the investigated cases.
The analysis of the results from BEO “Moussala” confirms the impact of the volcanic eruptions and Etna volcano, in particular, for the increasing of CO2 concentration in the atmosphere. On the other side, it was established that the activity of Etna is not the only factor which has impact on the concentration of CO2. More detailed analyses concerning not only natural, but also anthropogenic factors have to be done in the future in order to clarify the reasons for the increasing concentration of CO2 in the atmosphere (IPCC, 2014).

Volume XII |

The impact of the drought on the main crops cultivated in Northeastern Bulgaria

Abstract: Drought is one of the consequences of a reduction of rainfall over a long period of time. Often a number of meteorological elements as high temperatures, strong winds and low relative humidity occurs in conjunction with the drought. These facts make drought very strongly expressed. The present paper aims to analyze the intensity and the seasonal differences of meteorological drought in Northeastern Bulgaria and to characterize the drought impact on the main crops cultivated in the study area. The tendencies of the seasonal and the annual air temperatures and precipitation are investigated. Drought periods are revealed on the base of precipitation anomalies and the drought indices as Standartized Precipitation Index (SPI) and De Martonne Index. The driest years for the period 1961 – 2011 have been established. The production of the main crops in the study area is analyzed on the background of climate change. The information from climate models is used in order to describe future climate and to make the recommendations for crop cultivation in relation to climate impact.

Volume XI |

Changes in air temperature and precipitation and impact on agriculture

Abstract: Air temperature and precipitation are among the main factors for agricultural production. The aim of the present research work is to analyse changes in air temperature and precipitation in non-mountainous part of Southern Bulgaria in terms of the opportunities for the development of agriculture in the region. The trend in variability of seasonal and annual air temperature and precipitation is determined by the linear regression method. An analysis of the combination between air temperature and precipitation gives a tool to classify the climate according to dry and wet conditions of the territory. For this purpose the Gaussen-Bagnouls classification method is used in the present paper. In terms of air temperature, the investigated area is favourable for growing thermophilic plants. In order to investigate thoroughly the impact of climate change, the quantitative research has been complemented by a qualitative study – case study of farmers from the region of Stara Zagora. Case studies show that farmers are vulnerable to various degrees to the expected annual variability and average changes in yields depending on farm size, crop varieties and availability of irrigation.