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Climatology

Volume XVIII |

Climate parameters relevant for avalanche triggering in the Făgăraș Mountains (Southern Carpathians)

Abstract: The climate conditions may contribute significantly to the generation of several hazards in mountain areas, such landslides, wildfires, flash floods and avalanches. This study examines the variation of the main meteorological parameters with impact on avalanche triggering conditions at Bâlea-Lac Meteorological Station. At the best of our knowledge, this is the first overview of the basic climate parameters which are potentially avalanche triggers in the Făgăraș Mountains (Southern Carpathians). The study is based on data from only one weather station (Bâlea-Lac) from the period 1979-2017, assuming it is consistently relevant from climatic point of view for avalanche occurrence in the area. The results demonstrate that the theoretical circumstances for avalanche triggering (e.g. snow pack, fresh snow or wind) can be captured. This paper briefly describes the nivologic monitoring system run by the National Meteorological Administration and emphasises its utility for avalanche forecasting and alerts.

Volume XVIII |

Tracing the development of weather radar technology in Romania and worldwide

Abstract: Almost 90 years from the radar invention, the radar technology has evolved enormously and today it presents itself as an instrument of great importance in various research areas (meteorology, aviation, astronomy, air-ecology etc.). The main objective of the article is to identify the periods of development at the global level and also in Romania, as well as to identify the technology of most operational weather radars today. The article is based on publications from international journals and scientific books, covering the period of 1930-2018. The overview presentation demonstrates the reasons today’s weather radar is a powerful tool for studies concerning the atmospheric precipitations prediction, wind speed and direction, rainfall risk assessment and implementation of weather forecasts. Knowing the technological development is needed for the construction of the new generation radar and for exceeding the actual limits with regard to the accuracy of the radar data and the limits of observation. The purpose of this article is to summarize the evolution of the weather radar, with emphasis on the first experiments carried out during the analogue and digital period.

Volume XVIII |

A review of recent studies on heat wave definitions, mechanisms, changes, and impact on mortality

Abstract: Heat waves (HWs) represent a major danger to society and natural environment. The increasing occurrence of high magnitude and impact HWs has raised concerns worldwide and has attracted an increasing interest on this issue among climatologists over the past decade. In this review the research from 2007-2018 period on HWs definitions, driving mechanisms, present changes, future changes, and impact on human mortality is summarized. By reviewing the recent literature, it was found that whilst the atmospheric dynamic is considered to be the primary driver in HW occurrence, the sea surface temperature (SST) and land surface conditions are also essential driving components. The vastness of HW-definitions raises difficulties in selecting the appropriate methodology to identify heat episodes and to compare results from studies which used different definitions. However, by analyzing a sample of 109 papers, a preference for percentile-based definitions was observed. Therefore, 71.6% of the analyzed articles used only percentile-based definitions to identify HWs. Despite the wide variety of definitions, the analysis of changes in HWs converged to similar results. Thus, the existing recent literature provided extensive evidence of significant increase in HWs characteristics across large regions of the planet. Available scientific literature indicated that HWs have been responsible for a considerable increase in mortality in many regions of the world. In the future HWs are predicted to increase in their main characteristics leading to a greater impact on human mortality. Nevertheless, the implementation of rigorous adaptation measures can mitigate the negative impact on mortality. In conclusion, it was noted that a substantial progress has been done in the HW research, but there are still important gaps in this issue which need to be addressed.

Volume XVIII |

Aridity risk in the west of the Oltenia Plain: natural factors and human impacts on land degradation

Abstract: The lands of southern Oltenia had different evolution stages in the last century being influenced by the climatic factor but especially by the anthropic factor. From the extensive areas of ponds and marshes in the pre-war period to drainage, embankments, irrigation systems and planting of the windbreakers and shelterbelts in the 50s – 60s (reflected in the agricultural peak of the 70s – 80s) and to the present day, we are witnessing the aridization of the lands and the extension of the predominantly sandy areas, impracticable to the current type of agriculture.
After 1990, agriculture in the southern part of the Oltenia Plain had an accelerated decline caused by the destruction of the irrigation systems, the deforestation of the windbreakers and shelterbelts, the situation of land ownership and the failure of the adaptation of the crops to the soil types. In 2012 the percentages of irrigated areas reached 0% capacity used out of 76,820 ha in the Blahnița Plain and 1% capacity used out of 299,621 ha in the Oltenia Plain. All these have led to land degradation and amplification of geomorphological processes, especially on sandy surfaces, where the lack of vegetal layer together with the wind process lead to destabilization and movement of sand dunes. This article aims to conduct a spatial-temporal analysis of several types of lands exposed to drying, whose surface has increased considerably to almost 50,000 hectares. Another 50,000 hectares are predisposed to this phenomenon in the Oltenia Plain, on the western part of Jiu. An environmental management strategy for a sustainable development could be made for the protection of the lands against the winds by planting windbreakers and shelterbelts of fast growing species (acacia, hybrid poplar, wild pine, walnut tree). The research methodology involved the processing of the annual average data on temperature, precipitation and wind direction from the weather stations in south-west Oltenia, the processing of the data from the Landsat, Corine maps, as well as the analysis of the data provided by the examination reports on the occupation of land offered by the Ministry of Regional Development and Public Administration. In the analysis of land degradation as a result of the aridization process, the situation of the current vegetation layer was taken into consideration using the NDVI (Normalized Difference Vegetation Index) and data taken from Corine Land Cover between 1990 and 2006 regarding the change of the land use in the Oltenia Plain.

Volume XVII |

Considerations on the Influence of Micro Urban Heat Islands to the Temperature – Humidity Index During July 2017 in Craiova City Centre

Abstract: According to the National Administration of Meteorology, July 2017 was the hottest July months in the last decade, with one of the longest period with canicular temperatures in the last decades, too. In many regions of Romania, including Oltenia and Craiova city, too, yellow or orange code warning had to be announced. To determine real thermal discomfort sensation felt by the population of Craiova city, experimental research concerning micrometeorological measurements of the real temperature and relative humidity that contribute to the local Temperature – Humidity Index (THI) value was performed. According to the experimental research results, confirmed by using thermovision too, in Craiova city centre, five micro urban heat islands (MUHI) were identified. For three streets and a public square, despite the small mean value of relative humidity, due to the temperature’s high mean value, in these hot spots the THI mean average was 89.97, and for this thermal discomfort sensation, special protection measures would be needed. The same air micrometeorological parameters in these four hot spots were compared with the ones recorded in English Park, where due to vegetation and trees’ shadow, the THI average was 84.11, thus the real thermal discomfort sensation would have made necessary adequate protection measures. In order to study the intensity and spatial pattern of the MUHI, thermal infrared remote sensing (thermovision) was used to observe the surface of MUHI as a complementary indicator of the thermal discomfort sensation with in MUHI. The paper presents relevant interdependence relationships between the near surface air temperatures and pavement/ buildings surface temperatures that have been found for MUHI in Craiova’s city centre. The paper proposes practical methods that could be used to decrease the pavements’ and buildings’ walls temperatures, thus contributing to the decrease of THI in the MUHI within Craiova city centre.