Tadeusz Niedźwiedź

TRENDS OF MAXIMUM AND MINIMUM DAILY TEMPERATURES IN CENTRAL AND SOUTHEASTERN EUROPE

Changes in maximum and minimum daily temperatures (TMAX and TMIN, respectively) in nine selected regions of central Europe and in Bulgaria during 1951–1990 are investigated. Average series for central Europe are compiled and analyzed by linear trend analysis and the kernel smoothing. The increase in the annual TMAX in central Europe was, during 1951–1990, slightly lower than that of TMIN (0ċ52°C and 0ċ60°C, respectively). This results in a small decrease in the daily temperature range (DTR) by −0ċ08°C. With the exception of the spring TMIN other linear trends are insignificant. The observed insignificant trends in DTR in the central European region are related to small cloudiness changes. Long-term fluctuations of annual TMAX, TMIN, and DTR for eight selected series during the twentieth century are also investigated.

Variability of high rainfalls and related synoptic situations causing heavy floods at the northern foothills of the Tatra Mountains

This contribution provides the basics of the climatology of the Polish Tatra Mountains in a nutshell, with particular reference to intense precipitation and its relation to atmospheric circulation. Variability of various precipitation characteristics, including selected indices of intense precipitation in Zakopane and at Kasprowy Wierch, is illustrated in this paper. None of the trends in these characteristics and indices calculated for the entire time interval exhibit a statistical significance, but short-time fluctuations are evident. The occurrence of intense precipitation in the Tatra Mountains is strongly related to three circulation types. These situations (Nc, NEc, Bc) are associated with cyclones following track Vb after van Bebber. In addition to changing frequencies of circulation, this study also reveals an increase in the frequency of the circulation types associated with extreme precipitation.

Floods at the northern foothills of the Tatra Mountains — A Polish-Swiss research project

The present paper introduces the topical area of the Polish-Swiss research project FLORIST (Flood risk on the northern foothills of the Tatra Mountains), informs on its objectives, and reports on initial results. The Tatra Mountains are the area of the highest precipitation in Poland and largely contribute to flood generation. The project is focused around four competence clusters: observation-based climatology, model-based climate change projections and impact assessment, dendrogeomorphology, and impact of large wood debris on fluvial processes. The knowledge generated in the FLORIST project is likely to have impact on understanding and interpretation of flood risk on the northern foothills of the Tatra Mountains, in the past, present, and future. It can help solving important practical problems related to flood risk reduction strategies and flood preparedness.

Past and current climate change

This section describes long-term observed climatic changes in atmospheric parameters. The focus is on surface climate conditions, but changes in atmospheric circulation are discussed as they often are behind climatic variability seen on regional and local scales. For a summary introduction on mean atmospheric states and conditions in the Baltic Sea Basin see Annex 1.2 with sections on the general atmospheric circulation (A.1.2.1), surface air temperature (A.1.2.2), precipitation (A.1.2.3), clouds (A.1.2.4), and global radiation (A.1.2.5).

Decadal variability of floods in the northern foreland of the Tatra Mountains

Floods in the northern foreland of the Tatra Mountains considerably contribute to the total flood damage in Poland. Therefore, the question whether the magnitude and frequency of floods have changed in this region is of high interest. This study aims at investigating the inter-decadal variability of magnitude, frequency and seasonality of floods since the mid-twentieth century, to better understand regional changes. The analysis was accomplished in a multi-temporal approach whereby trends are fitted to every possible combination of start and end years in a record. Detected trends were explained by estimating correlations between the investigated flood parameters and different large-scale climate indices for the northern hemisphere, and by trends found in intense precipitation indices, number of days with snow cover, cyclonic circulation types, temperature and moisture conditions. Catchment and channel changes that occurred in the region over the past decades were also considered. Results show that rivers in the area exhibit considerable inter-decadal variability of flows. The magnitude and direction of short-term trends are heavily influenced by this inter-decadal variability; however, certain patterns are apparent. More extreme, although perhaps less frequent floods are now likely to occur, with a shift in the seasonality, decreasing flood magnitudes in winter and increasing during autumn and spring. The identification of the factors contributing to the occurrence of flood events and their potential changes is valuable to enhance the flood management in the region and to improve the resilience of the population in this mountainous area.

Recent warming on Spitsbergen—Influence of atmospheric circulation and sea ice cover

Spitsbergen has experienced some of the most severe temperature changes in the Arctic during the last three decades. This study relates the recent warming to variations in large-scale atmospheric circulation (AC), air mass characteristics, and sea ice concentration (SIC), both regionally around Spitsbergen and locally in three fjords. We find substantial warming for all AC patterns for all seasons, with greatest temperature increase in winter. A major part of the warming can be attributed to changes in air mass characteristics associated with situations of both cyclonic and anticyclonic air advection from north and east and situations with a nonadvectional anticyclonic ridge. In total, six specific AC types (out of 21), which occur on average 41% of days in a year, contribute approximately 80% of the recent warming. The relationship between the land-based surface air temperature (SAT) and local and regional SIC was highly significant, particularly for the most contributing AC types. The high correlation between SAT and SIC for air masses from east and north of Spitsbergen suggests that a major part of the atmospheric warming observed in Spitsbergen is driven by heat exchange from the larger open water area in the Barents Sea and region north of Spitsbergen. Finally, our results show that changes in frequencies of AC play a minor role to the total recent surface warming. Thus, the strong warming in Spitsbergen in the latest decades is not driven by increased frequencies of “warm” AC types but rather from sea ice decline, higher sea surface temperatures, and a general background warming.

Change in Atmospheric Circulation Patterns

This chapter examines both variability and trends in atmospheric circulation favouring the occurrence of flood precipitation defined as daily totals ≥30, ≥50 and ≥100 mm in warm half-year (May–Oct) and in summer (JJA). We used a catalogue of circulation types created for the Upper Vistula Basin, and related circulation indices (zonal circulation index, meridional circulation index, cyclonicity index and NAO) covering the 1874–2015 period. Climatology of atmospheric circulation over the Upper Vistula Basin is discussed as a basis for further investigations. In order to select circulation types and indices impacting both the occurrence and long-term variability of flood precipitation, we calculated the frequency and conditional probability of high precipitation (≥50 mm) in circulation types and correlation between selected circulation characteristics and high precipitation frequency (≥30 mm). Trends in the frequency of circulation types and indices favouring the occurrence of high precipitation were calculated to assess current and possible future flood conditions. In summer and warm half-year the Upper Vistula Basin was usually under an influence of anticyclonic wedge (Ka circulation type) and cyclonic trough (Bc circulation type). Circulation types with the air flow from the west (Wa and Wc) were the most frequent of all advectional types. The occurrence and long-term variability in flood precipitation over the Upper Vistula Basin were strongly linked to the frequency of air advection from the north and north-east under an influence of low pressure system (Nc and NEc circulation types) and to Wi—zonal circulation index at both stations in summer (JJA) and to Ci—cyclonicity index at Kasprowy Wierch station in warm half-year (May–Oct). Trends in majority of circulation characteristics favouring the occurrence of high precipitation and impacting its long-term variability were not statistically significant with an exception of the frequency of Nc type and Ci index in the warm half-year and Wi index in summer. Significant increase in the number of days with Nc circulation type and the cyclonic situations (Ci index) in warm half-year and intensification of air advection from the north-east in summer may lead to increase in the frequency of flood conditions in these seasons. Regardless insignificant trends, the variability in the NEc frequency considerably determines the occurrence and long-term variability of high precipitation thus was recognized as indicator of flood conditions. There was intensification of the air advection from the north (Nc) in the warm half-year (May–Oct) in the 50-year period between 1930 and 1980. High frequency of NEc type was found in seventies and eighties which coincided with the high frequency of floods in those decades in Poland and at the turn of the first and second decades of the 21st century. Low frequencies of these circulation types during 1982–1995 were in phase with relatively dry conditions in Southern Poland without the floods within the Upper Vistula Basin. In the further more wet years the great floods happened in July 1997 and May 2010.

FREQUENCY OF ICE DAYS AT SELECTED METEOROLOGICAL STATIONS IN SVALBARD

Abstract The paper aims to present research into both the long-term variability in the ice days in Svalbard representing the Atlantic sector of the Arctic, and their relations to atmospheric circulation. Ice days are defined as days with a daily maximum temperature below 0°C (Tmax<0°C). They are considered to be amongst the most important indices of current climate change. All the available data on daily maximum air temperature from three Norwegian stations (Svalbard Airport (Svalbard Lufthavn), Bjørnøya and Hopen) and from the Polish Polar Station in Hornsund (SW Spitsbergen) have been employed. The relevance of atmospheric circulation to the frequency of the occurrence of ice days was evaluated by calculating the Spearman correlation coefficients between the frequency of ice days and three regional circulation indices: zonal westerly circulation index (W), meridional southerly circulation index (S) and index of cyclonicity (C). At all the stations the number of ice days exhibited significant decreasing trends in the period of 1979-2012.

Flood Risk in the Upper Vistula Basin

The Upper Vistula Basin covers a large part of Southern Poland. This area is very diverse, as it comprises of various geographical regions formed during different geological periods what can be seen in its multifarious composition (Carpathian Mountains, Subcarpathian basins, Lesser Poland Uplands). Culturally, it combines a range of secular traditions formulated by different tribes, in particular by its original inhabitants. The majority of the first cities were founded as trade centers (13th–16th century), later transformed into tourist or industrial centers (19th–20th century). The subregions of the Upper Vistula Basin like Silesia, Cracow, Bielsko-Biała, Tarnów–Rzeszów, Tarnobrzeg–Stalowa Wola, continue to develop coal, chemical, steel, light and food industries. Nowadays, these cities are very well connected by a modern grid of motorways, expressways and railways enabling a faster development of the region. Agriculture has been a pillar of economy for the inhabitants of northern part of the Upper Vistula Basin where soils are rich, whereas in the Carpathians where the soils were poorer, only pastoral farming could be developed. In spite of the industrial activity in the region, the natural environment hasn’t been modified much so far what makes it even more attractive for tourists who numerously visit wild and well preserved national parks of the regions, in particular the Tatra National Park. The Upper Vistula Basin is of a great importance in the hydrology of Poland, and its influence goes far beyond its watershed. It embraces the headwater area of the largest river in Poland, i.e. the River Vistula and its tributaries. The water resources (precipitation, river runoff) of the area are the richest in the whole country. The water cycle dynamics in the mountain area is very high due to steep relief, low permeability of the ground, and flood formation develops fast. It has been favoured by intensive surface and subsurface flow in the area with a dense agricultural land fragmentation and field road network.

Long-term variability of occurrence of precipitation forms in winter in Kraków, Poland

The paper discusses long-term change in snowfall, rainfall and mixed precipitation viewed in conjunction with air temperature and North Atlantic Oscillation (NAO) in winter (December–February). In the study of contemporary climate change and its effect on the hydrological cycle it is useful to focus on winter precipitation forms. A 146-year secular observation series from Kraków, spanning the period 1863–2008, was used to extract data on the number of days with precipitation and on precipitation amount broken down by form. Statistically significant trends were found in total and mixed precipitation, but not in snowfall and rainfall. The climate warming effect has contributed to a material decrease in the snowfall to total winter precipitation ratio during the second half of the 20th c. The highest impact of air temperature was found in the wintertime variation in number of days with snowfall while the NAO had a significant influence on the frequency and amount of both rainfall and snowfall.