Dariusz Wrzesiński

Effect of the North Atlantic Oscillation on the Thermal Characteristics of Lakes in Poland

This paper presents the effect of the North Atlantic Oscillation (NAO) on the thermal characteristics of lakes in Poland. In the analysis, the use was made of monthly air temperatures recorded at fifteen meteorological stations, water temperatures of twelve lakes, and Hurrell’s winter NAO indices. Over the study period (1971–2010), there was a marked increase in the temperatures of both, air and lake waters. Depending on the NAO phase, water temperatures were observed to depart from mean values, being markedly higher than average (even by 1°C) in the positive winter NAO phase. The differences in water temperatures were statistically significant in the winter-spring season. In turn, in the negative NAODJFM phase lake water temperatures in winter and spring were markedly lower than average (in March even by 1.0°C). The unique response of some lakes depends on their morphometric parameters, including their mean depth.

Regional differences in the influence of the North Atlantic Oscillation on seasonal river runoff in Poland

Regional differences in the influence of the North Atlantic Oscillation on seasonal river runoff in Poland In this paper, an analysis of monthly and seasonal runoff volumes in two stages of the North Atlantic Oscillation are presented. The analysis embraced runoff at 146 profiles located on 96 Polish rivers during the years 1951-2000. The changes in the runoff conditions of Polish rivers in the two NAO stages and their spatial diversity were determined based on the differences between runoff observed in the years of exceptionally high (NAODJFM > 2,0) and low (NAODJFM < -2,0) values of the winter NAO index. The results of the research indicate that the influence of the North Atlantic Oscillation on the runoff of Polish rivers is diverse in terms of time and space. A classification of rivers was made in terms of the similarity of deviations of their seasonal runoff between the different NAODJFM stages. In the classification procedure use was made of Wards method of hierarchical grouping. In this way, five classes of the river profiles under analysis were obtained. Environmental conditions in the catchments and hydrological regime features clearly influence the regional differences in the impact of the North Atlantic Oscillation on the flow of rivers.

Use of Entropy in the Assessment of Uncertainty of River Runoff Regime in Poland

The objective of this paper is to describe spatial differences in the uncertainty of features of the runoff regimes of Polish rivers based on entropy in Shannon’s information theory. They included: the entropy of monthly river runoff and the entropy of river runoff distribution over time. An analysis of monthly flow series for the years 1951–2010 from 395 gauging stations located on 248 rivers in Poland was performed. This allowed a quantitative determination of the degree of uncertainty of two regime characteristics indirectly establishing the predictability, regularity, and stability of their appearance and their spatial variability. An analysis of relations between the calculated entropy, as well as between the entropy and the classical parameters commonly used was performed in describing the hydrological regime. The obtained grouping of rivers into four categories in terms of entropy of volume and distribution of runoff in the annual cycle clearly coincides with the types of river regime distinguished in Poland.

Long-term changes in the hydrological regime of high mountain Lake Morskie Oko (Tatra Mountains, Central Europe)

Abstract The paper discusses changes in the hydrological regime of high mountain Lake Morskie Oko located in the Tatra Mountains, in the Tatra Mountains National Park, a UNESCO biosphere reserve (MaB). According to the research conducted in the years 1971–2015, its water stages decreased by 3.5 cm·dec−1, mean annual water temperature increased by 0.3°C·dec−1 and the duration of ice phenomena and ice cover was reduced by 10 day·dec−1. No considerable changes in maximum values of ice cover thickness were recorded. Such tendencies are primarily caused by long-term changes in climatic conditions – air temperature and atmospheric precipitation. The hydrological regime of the lake was also determined by changes in land use in the lake’s catchment and its location in high mountains.

Uncertainty of Flow Regime Characteristics of Rivers in Europe

Abstract The aim of the paper is to describe spatial differences in the uncertainty of features of the flow regimes of rivers in Europe on the basis of measures whose methodological assumptions derive from Shannon’s information entropy theory (1948). They included: the entropy of monthly flow volumes, the entropy of the flow distribution over time, and the entropy of maximum and minimum monthly flows. An analysis was made of monthly flow series for the years 1951-1990 from 510 gauging stations located on 369 rivers in Europe. It allowed a quantitative determination of the degree of uncertainty of the four regime characteristics, indirectly establishing the predictability, regularity and stability of their appearance and their spatial variability. In the procedure of identification of spatial differences among rivers concerning the uncertainty of their flow regime features, use was made of local indices of spatial dependence. On application of LISA (Local Indicators of Spatial Association) based on Moran’s local Ii statistic, a typology of rivers was obtained in terms of the kind and statistical significance of spatial associations involving the uncertainty of the flow regime variables in question.

Effect of the North Atlantic Oscillation on Ice Phenomena on Selected Lakes in Poland Over the Years 1961–2010

Abstract An analysis is presented of changes in the parameters of ice phenomena on selected Polish lakes over the years 1961-2010 against the background of variations in the intensity of the North Atlantic Oscillation. The following features were analysed: the start and end of ice phenomena and ice cover, their duration, and the stability of ice cover at observation sites of the Institute of Meteorology and Water Management on lakes located in various physical-geographic regions. Multi-year tendencies of change in the ice parameters under study were identified. The most statistically significant negative trends were observed for the ending dates of ice phenomena and their duration. Changes in the ice characteristics in the different NAODJFM stages were determined on the basis of their deviations: between years with high (> 1.7) and low (< -1.09) values of the winter NAO index, and from average values from the years 1961-2010. Changes in the intensity of the North Atlantic Oscillation affect all the parameters of ice phenomena except their starting dates. In a negative NAODJFM stage, ice phenomena and ice cover end later and last longer; also, the maximum thickness of ice cover is greater, its forms later and is more stable than in a positive stage and in average conditions

Detection of changes in flow regime of rivers in Poland

Abstract The aim of this study is to detect changes in flow regime of rivers in Poland. On the basis of daily discharges recorded in 1951-2010 at 159 gauging stations located on 94 rivers regularities in the variability of the river flow characteristics in the multi-year period and in the annual cycle were identified and also their spatial uniformity was examined. In order to identify changes in the characteristics of river regime, similarities of empirical distribution functions of the 5-day sets (pentads) of discharges were analyzed and the percent shares of similar and dissimilar distributions of the 5-day discharge frequencies in the successive 20-year sub-periods were compared with the average values of discharges recorded in 1951-2010. Three alternative methods of river classification were employed and in the classification procedure use was made of the Ward’s hierarchical clustering method. This resulted in identification of groups of rivers different in terms of the degree of transformation of their hydrological regimes in the multi-year and annual patterns.

Effect of the North Atlantic Oscillation on the Pattern of Lake Ice Phenology in Poland

ab]AbstractThis paper presents an analysis of the influence of the North Atlantic Oscillation on the pattern of lake ice phenology in Poland. The research embraced 22 lakes in Poland over the period 1961–2010. Strong relations were found to hold between NAO and individual characteristics of ice phenology. In a negative NAO phase, one can observe a later appearance of ice phenomena and ice cover compared with the average values, ice cover persisting even 30 days longer and being thicker even by more than 10 cm. In turn, in a positive NAO phase the duration of ice phenomena and ice cover is shorter, the cover being less thick and solid. The observed spatial differences in the effect of NAO on the pattern of ice phenomena in Poland show this matter to be fairly complex. The most significant factor changes in climatic conditions, which manifest themselves in the continentality of the climate growing eastwards.

Water level changes in Polish lakes during 1976-2010

The paper presents the analysis of tendencies in water level changes in 32 lakes in Poland during 1976–2010. Series of monthly, seasonal, and annual precipitation and air temperature for 9 meteorological stations were also studied. The trend analysis for all of the studied series of water levels in lakes showed high spatial and temporal variability. Series of annual water levels in the case of 6 lakes showed statistically significant increasing tendencies, and in 7 lakes, significant decreasing trends. Series of annual amplitudes in the majority of lakes (22) showed a decreasing trend, but they were statistically significant only in three cases. The tendencies for air temperature fluctuations are more statistically significant than precipitation. The key role in determining water level changes is played by local factors, particularly including human economic activity, obscuring the effect of natural factors on water level changes. The paper describes cases of changes in water levels in lakes under anthropopressure related to among others: agricultural irrigations, hydropower infrastructure, water transfers, navigation, or mining.