Climate of the Romanian Carpathians

Mountain regions are a key issue at global scale, their importance having been recognized at the United Nations Conference on Environment and Development (Rio de Janeiro, 1992) and further underlined by designating the year 2002 as International Year of Mountains (IYM). The global warming put critical challenges to mountain environment and related ecosystem services as mountain regions proved to be particularly vulnerable to climatic fluctuations. From many perspectives, the Carpathian Mountains have a decisive role for the Central and South Eastern Europe, shaping the landscape, or influencing the culture and human development. This book tackles mainly the climate characteristics and the observed trends in the Romanian Carpathians (1961–2010), but it also presents estimations regarding the climate projections through the next decades (2021–2050). It is designed to address the needs constantly expressed by a large variety of users, from students and mass media to policy makers, land planning actors, water managers, and economic operators.

The chapter is organized in two sections. The first section overviews the main impulses, initiatives and achievements in global and European environmental research targeting mountain regions since the early 1970s until 2012 (the Rio +20 Conference). This section also highlights how the growing significance of the climate change issue in global environmental research agendas and of the potential climate change impacts in mountain environments, has promoted mountain regions to a next stage of importance, as they are currently widely recognized as “early indicators of climate change”. The main achievements of the Mountain Research Initiative in promoting the research in the Carpathian region and building opportunities for future collaborations targeting this region are also emphasized. The second section outlines the main contributions to the knowledge of the climate and weather of the Romanian Carpathians. The survey of the Romanian specialist literature shows a general lack of comprehensive studies carried out on the Romanian Carpathians as a whole, only a few aiming at revealing the regional patterns of a distinct climatic feature, usually derived from short period of observations of less than 10 years.

Developed as the most extended and contorted sector of the European Alpine System, the Carpathians represent a complex natural environment whose present-day morphology is marked by active human intervention. Their limits and subdivisions were subjected to numerous geomorphic classifications, meant to separate heterogeneous units characterized by common lithological, structural or geomorphic traits. The longest sector of this European mountain range is in Romania, containing up to 40.9 % of the total Carpathian surface and 27.8 % of the country’s territory. In response to a complex process of orogeny, outlined by polycyclic uplift-denudation sequences, the Romanian Carpathians Chain reflects in its morphology, morphometry and morphodynamic patterns, the litho-structural conditioning. The general physiographic disposition of the chain and the local morphometry, imposed by the folded and faulted igneous, metamorphic or sedimentary deposits, are conditioning the hydrological, climatic and biologic characteristics in terms of horizontal and vertical zonation, as well as in the temporal distribution of composing agents, processes and forms.

This chapter gives information about the meteorological and ancillary datasets used in this work, including the description of the meteorological variables, their temporal coverage, the spatial distribution of the weather stations with homogenized datasets and the gridded data sources accessed (e.g. geographical, meteorological). The main steps in the development of the mountain meteorological network since the late 1920s to date and its general characteristics (e.g. number of stations, density, spatial representativity) are also summarized in a section of the chapter.

This chapter is organized in four sections, which refer to the homogenization algorithm applied to the meteorological data, the statistical methods, the spatialisation methods used to derive the climatological maps and the regional climate models used to derive the future changes in the climate of the Romanian Carpathians. The homogenization was done using the Multiple Analysis of Series for Homogenization (MASH v3.03) method and software and the gridding was based on the Meteorological Interpolation based on the Surface Homogenized Data Basis (MISH v1.03) software, whose results were successfully applied within the CARPATCLIM project. The main statistical methods applied in the climatic analyzes are the Mann-Kendall trend test, the Kendal-Theil slope estimation and the Spearman rank correlation coefficient. Interpolation surfaces of climate variables have been constructed using the Regression Kriging method, which combines a multivariate regression model with kriging of the regression residuals. The climate change signals until 2050 were derived from the outputs of three Regional Climate Models (RegCM3, ALADIN-Climate, and PROMES) at 25 km spatial resolution, under A1B IPCC scenario.

This chapter outlines the importance of three major factors and the effects of their joint action in defining local and regional climatic features of the Romanian Carpathians: latitude and longitude, topography and the regional atmospheric circulation. The chapter summarizes the role of latitude and longitude in shaping the distribution of the direct and global solar radiation across the Romanian Carpathians and highlights the main influences of regional atmospheric circulation in defining local weather aspects and the regional climatic patterns in this mountain range. The complexities introduced by the main topographic characteristics of the underlying mountain terrain (e.g. altitude, slope aspect and angle, landforms) on climate state variables, are addressed here based on the key findings of several previously published works, focusing on local climate contrasts and climate zonation aspects within the Romanian Carpathians. A major focus is on the altitude effect, imposing the overall climatic zonation, as revealed by on the key findings of several previously published works.

This chapter provides a description of the main climatic conditions of the Romanian Carpathians region based on the analysis of the regime of the most important climatic parameters such as air temperature, precipitation, wind and snow. The regional climatic patterns are discussed in terms of elevation effect, influence of the prevailing atmospheric circulation and seasonality, aiming at distinguishing between the climate variation particularities emerging between three main units. The analysis highlights the climatic differentiations between the areas above 800 m and those below 800 m, generally including most of the intra-Carpathian depressions. The absolute climatic records derived from in situ measurements are presented in tabular form.

This chapter analyses the recent climatic trends in the Romanian Carpathians, with an accent on seasonal changes. Temperature trends are increasing in winter, spring and summer, while they are completely absent in autumn, which is the single stable season from a thermal point of view. On the other hand, autumn is the only season when significant increasing trends in precipitation have been found. The average wind speed is decreasing in all seasons, confirming most of the findings regarding the general tendency in the Northern Hemisphere. Snow-related trend analysis shows general decreasing trends in mean snow depth, number of days with snow cover, number of days with snowfall, and continuous snow cover duration. The increase in temperature at most of the locations, together with the slight decrease in winter precipitation explains the reduction of the snowfall days. The number of snowfall days, snow duration and mean snow depth present strong negative correlations with the NAO index for the same period (DJF). The large-scale circulation over the North Atlantic has a considerable effect on the winter season in the Romanian Carpathians.

Several indices of climate extremes – based on minimum and maximum temperature, daily precipitation and daily snow cover – were used in order to check for changes over 1961–2010. The most important changes were found in maximum and (to a lesser extent) in minimum seasonal temperature. The warming signal is well retrieved in the trends in thermal-related extreme indices. Autumn is the only stable season with respect to changes in temperature extremes. Precipitation extremes exhibit no consistent change, leading to the conclusion that the decreasing trends in the snow-related indices, especially the maximum length of snowfall spells are rather related to recent warming.

This chapter briefly presents the changes of the air temperature and precipitation amounts predicted by Regional Climate Models for the next decades over the Romanian Carpathians. The analysis refers to the IPCC Scenario A1B, and exploits the outputs of several European projects developed in the recent years. The air temperature is likely to increase in all seasons, while the precipitation amounts will generally vary with ±10 % as compared to the present climate, at different spatial rates. The most significant temperature increasing is expected to occur in summer; over most Carpathian areas, the period 2021–2050 will be 2.5–3.0 °C warmer than 1961–1990. As regards the precipitation, the winter will be sensibly drier, while increasing trends are specific to the autumn.

‘Complexity’ is perhaps the term that defines mountain climatology in the most relevant manner, as it can be associated with many aspects in this direction. Mountain environments are always characterised by complex physical background generated at the interaction of many factors, leading to multiple consequences, creating specific resources, and impacting various social and economic interests. In this context, mountain climatology research has a crucial importance for understanding the relationships between the system’s components, for preventing potential threats, and mitigating their impact, and for a sustainable use of the natural resources. This book is a climatic monograph which addresses one of the most complex mountain environments in Europe, the Carpathians Chain, focusing on the mountain regions which lie over Romania, herein called Eastern, Southern, and Western Carpathians.