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.

Volume X |

Observed changes in precipitation in the Danube river lower basin in the context of climate change

Abstract: The study presents the observed variability and changes in precipitation regime in the Danube river lower basin, which is situated along both sides of the border between Bulgaria and Romania. The research is based on monthly precipitation totals recorded at 22 meteorological stations from Bulgaria and Romania. The investigated period is 1961-2007 out of which two reference periods are considered, the last 30 years (1978-2007) and the usually used WMO reference for the contemporary climate (1961-1990). The main objective of the study is to give actual information about precipitation variability in the region in the context of global climate change. The results of the work point out on some characteristics of extreme precipitation events in the region – drought and high precipitation, and on the role of natural mechanisms for precipitation variability. Based on the statistical methods we have used, the results can be summarized as follows: – Summer precipitation represents 30-35% of annual precipitation total followed by spring precipitation with about 25-28% of annual values. Autumn precipitation is between 22-24% of annual values in most of the stations. Winter precipitation represents about 20% of annual precipitation; – The wet periods have been observed at the end of the 1960’s and at the beginning of the 1970’s; – The intensive drought from 1983 to 1993 has been confirmed by calculating the precipitation indices like as Rainfall Anomaly Index and Cumulative Anomaly Index. The driest year during the investigated period was 2000; – Increasing occurrence of extremely wet months has been observed since 2002.