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 XVI |

Analysis of the Mean of Daily Maximum Temperature within the Romanian Plain (1961-2015)

Abstract: The present study aims at rendering the characteristics of the means of the daily maximum temperature at monthly, seasonal and annual level within the Romanian Plain, as well as their trends. The time series cover a 55-year period (1961-2015) and data come from 8 meteorological stations. In order to assess the distribution of the data, there were calculated two coefficients (Skewness – S and Kurtosis – K) and also applied the Kolmogorov-Smirnov test for normal distribution. The positive S values and negative K values indicate that the distribution is not symmetrical but, taking into account that the values are quite close to 0, we may assume, it is not far from normal. The KS test also indicates a normal distribution. Homogeneity of the annual temperatures was tested by means of Pettitt test, Standard Normal Homogeneity Test (SNTH) and t test, which emphasized that the change point was registered before 2000. At three stations (D.T. Severin, Bechet, Buzău) all three applied tests indicated the same year 1988, respectively 1989 as break point, while at the other stations, it is the same year according to SNHT and T test, and a different one based on MWP. Based on Mann-Kendall test and Sen’s slope estimation, there were emphasized temperature trends and their statistical significance. The highest temperature increase and upward trend was registered for mean annual and mean summer values (0.001 level of significance within the entire region). However, except for autumn, which is generally characterized by statistically insignificant negative trends, all the other seasons display significant upward trends. At monthly level, only the summer months registered upwards trends within the entire plain (level of significance oscillating between 0.05 and 0.001), while in autumn months there were not registered any statistically significant trends.

Volume XIII |

Analysis of precipitation characteristics and trends for the Getic Piedmont and Subcarpathians, Oltenia region, Romania

Abstract: Changes in precipitation characteristics of the hilly area of Oltenia, covering the western parts of the Getic Piedmont and SubCarpathians, were analysed, based on monthly rainfall data, for the timeframe 1961 to 2010. The precipitation trend analysis for the period 1961-2010 shows different results–increasing precipitation in winter half part of the year for most of the Subcarpathian area and a rainfall decrease in summer half of the year for the entire region. The piedmont part of the study area, with dominant agricultural land use, shows the highest spring precipitation decrease, whereas in the Subcarpathian area, summer and autumn precipitation increase is more pronounced. The positive trends are spatially the most homogenous in August, September and October, while the most uniform negative trends were recorded in February, May and November. At annual level, the most significant decrease corresponds to the piedmont, while the rest of the region displays an insignificant positive trend. The SPA emphasized that normal years (deviations oscillating between -1.00 and +1.00) predominate; however, in the eastern part of the region there are lower percentages compared to the western part (70-74% compared to 64-66%). At the same time, in the east, the share of dry weather is double compared to the western part, where rainy weather predominates.

Volume X |

Temperature – Humidity Index (THI) within the Oltenia Plain between 2000 and 2009

Abstract: Temperature-humidity index, also known as thermal comfort index, represents an extremely used index in mass-media nowadays; it renders an apparent temperature, namely the temperature felt by human body that cools slower at higher values of the relative humidity due to the reduction of the evaporation rate. THI is calculated on the base of several formulas, which corroborate air temperature and relative humidity, the critical threshold being 80. By analysing the statistical date supplied by the Regional Meteorological Center Craiova, it comes out that the years with the highest number of days with THI values above 80 are 2000, 2001, and 2007 for the entire studied territory, when, during summer, the region was affected by numerous heat waves, which led to the frequent exceeding of the 40°C value. The most affected area is located in the central-southern and eastern parts of the Oltenia Plain – 51 days with THI > 80 at Caracal in 2000, 47 days with THI > 80 at Bechet in 2001, and 41 days with THI > 80 at Băileşti in 2007. Regarding the monthly distribution, the most problematic months are, of course, July and August, when it is favoured the penetration of certain extremely hot air masses from northern Africa, as well as thermal convection. During the analysed decade, the highest monthly number of days with values above the threshold was registered at Caracal in August 2000 – 23, at Bechet in August 2001 – 25, and at Băileşti in July 2007 – 20. On the whole, in the 10 analysed years, we remark Băileşti – 76 days in July and 90 in August, Bechet – 84 days in July and 83 in August, and Calafat – 77, respectively 70 days. Increased values of THI mainly affect children and elderly people or those suffering of different diseases. At values lower than 70 of the THI, most of the people feel comfortable, at values comprised between 75 and 80, about half of the population feels thermal discomfort, while at values above 80, even if the discomfort sensation is not obvious, it is recommended to take adequate protection measures.

Volume IX |

Ecoclimatic Indexes within the Oltenia Plain

Abstract: The Oltenia Plain represents an important agricultural region of Romania, which displays vast surfaces that can be properly cultivated if one takes into account the climatic restrictions that generates a series of dysfunctions. In order to underline the problems related to the aridization tendency within the region, as well as to determine the most adequate plants, there were calculated many indexes used in different agroclimatic and biogeographical studies. Thus, according to the processed data, the Oltenia Plain generally belongs to the steppe and forest steppe domain and, with regard to the cultivable plants, there are recommended the thermophilous and xerothermophilous ones, which can get good productions even in the pluvial-thermal conditions characteristic to the region. The thermal regime imposes itself through a slight increasing tendency because of the extremely high values registered in summer, while the pluviometric regime registers obvious fluctuations and a decreasing tendency. Consequently, the issue related to the aridization of the southern part of the Oltenia Plain is confirmed, an issue that is presently stressed by other factors, such as massive deforestation, destruction of the irrigation systems etc., which led to the reactivation of certain areas covered by sands. However, the partial results of the study do not sustain the idea of desertification in the area.