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This study presents the direct relationships between changes in the annual surface temperature of the North Atlantic (SST) and the number of days per year experiencing low flows in the Warta River catchment (WRC) in Central Europe, Poland, in the multi-annual period of 1951–2020. The number of days experiencing low flows (TLF) was used to describe the conditions of hydrological drought in the WRC. Moderately strong (r~0.5) but statistically highly significant (p < 0.001) relationships were found between TLF and the SST in the subtropical (30–40° N, 60–40° W) and subpolar North Atlantic (70° N, 10° W–10° E). With the increase in the annual SST in these parts of the North Atlantic, the number of days in a year experiencing low flows in the WRC also increased. It was determined that besides synchronous (i.e., in the same year) relationships between TLF and SST, asynchronous relations also occurred: the SST changes were one year ahead of the TLF changes. With the increase in the SST in the subtropical and subpolar North Atlantic, the sunshine duration and air temperature in the WRC increased, while the relative humidity decreased. The relationships between precipitation in the WRC and SST were negative (from −0.04 to −0.14), but statistically insignificant (p > 0.2). This indicates that the impact of SST changes on TLF in the WRC is mainly caused by the shaping of the amount of surface evaporation, which strongly increases in years of high SST, and the climatic water balance becomes negative, resulting in an increase in extremely low flows. The analysis of the causes of these relationships shows that the SST changes in the North Atlantic control, through changes in the height of the geopotential (h500), changes in the atmospheric circulation over Europe. In the periods of SST h500 growth over Central Europe, the atmospheric pressure (SLP) increases. That area is more frequently than average under the influence of the Azores High; this leads to an increase in the frequency of anticyclonic weather. A significant increase in the number of TLFs and prolonged periods of hydrological drought in the WRC after 2000 are associated with a strong increase in the SST in the area of the tropical and subtropical North Atlantic. [ABSTRACT FROM AUTHOR]

The occurrence of long-lasting severe heat stress, such as in July–August 2003, July 2010, or in April–May 2018 has been one of the biggest meteorological threats in Europe in recent years. The paper focuses on the biometeorological and mortality effects of the hot June that was observed in Central Europe in 2019. The basis of the study was hourly and daily Universal Thermal Climate Index (UTCI) values at meteorological stations in Poland for June 2019. The average monthly air temperature and UTCI values from 1951 to 2018 were analysed as background. Grosswetterlagen calendar of atmospheric circulation was used to assess synoptic conditions of heat wave. Several heat strain measures were applied : net heat storage (S), modelled heart rate (HR), sultriness (HSI), and UTCI index. Actual total mortality (TM) and modelled strong heat-related mortality (SHRM) were taken as indicators of biometeorological consequences of the hot June in 2019. The results indicate that prolonged persistence of unusually warm weather in June 2019 was determined by the synoptic conditions occurring over the European region and causing advection of tropical air. They led to the emergence of heat waves causing 10% increase in TM and 5 times bigger SHRM then in preceding 10 years. Such increase in SHRM was an effect of overheating and overload of circulatory system of human organism. [ABSTRACT FROM AUTHOR]

Lake surface water temperature (LSWT) is a key indicator which drives ecosystem structure and function. Quantifying the impact of climate change on LSWT variations is thus of great significance. In this study, observed data of LSWT during the period 1969–2018 in a high mountain lake (Morskie Oko Lake, Central Europe) were analyzed. The results showed that the prominent warming of the LSWT and air temperature began around 1997. A logistic non-linear S-curve function was used to model monthly average LSWT. The non-linear model performed well to capture monthly average LSWT and air temperature relationships (Nash-Sutcliffe efficiency coefficient 0.86 and the root mean squared error 1.63 °C). Using the 2009–2018 period as base scenario, a sensitivity analysis was conducted. The results showed that the annual mean LSWT will likely increase about + 1.29 °C and + 2.64 °C with air temperature increases of + 2 °C and + 4 °C respectively at the end of the twenty-first century. If realized, such a scenario will cause serious consequences on lake ecosystem. [ABSTRACT FROM AUTHOR]

The aim of the research was to identify connections between the occurrence of heat load across Poland and large-scale factors, which will allow statistical models to be derived that are useful to describe bioclimatic conditions in Poland in the summer. Atmospheric circulation over the North Atlantic Ocean and Europe and near-surface air temperature over the central part of Europe were considered. The monthly frequency of the occurrence of combined "moderate, strong, very strong and extreme heat stress" based on the assessment scale of the Universal Thermal Climate Index (UTCI) in the summer months accounted for 6% to more than 30% of all cases. The statistical downscaling procedure of canonical correlation analysis (CCA) with respect to the period 1971–2000 was applied to extract the main modes of large-scale factors and their local responses. The greatest explained variance of local field response to atmospheric circulation as well as to near-surface air temperature is above 70%. Warm air flow from the east and from the southeast has the strongest influence on the increase in frequency of the occurrence of heat stress on human beings in Poland. The spatial differentiation of the air temperature anomaly over central Europe is an important determinant of the occurrence of heat stress in Poland. The validation of constructed models encompassed the periods 1951–1970 and 2001–2010. The best reliability of results was reached for the reconstructed series in July. The results are less useful in June and August and in the coastal region. [ABSTRACT FROM AUTHOR]

Atmospheric measurements over 5 years (2005-2010) at two sites in Łódź, central Poland have been analyzed to develop a better understanding of turbulence in urban areas. Fast response wind velocity, temperature, humidity and CO concentration were measured using sonic anemometers and gas analyzers, placed on narrow masts at 37 and 42 m above the ground. The measurements were used to calculate standard deviations of each parameter, and were then normalized according to local Monin-Obukhov similarity theory and plotted as a function of stability parameter ζ = z′/ L. Results for the wind components show typical scaling with a power law with exponent ±1/3 in the free convection limit, and that approaches a constant value close to neutral stratification. For stable conditions, the constant value in the neutral limit remains the same for stability parameters lower than 0.1-0.2, then increases. The normalized standard deviation of temperature fits the −1/3 law in the free convection limit, approaching a constant value within a stable limit. However, it exhibits hyperbolic characteristics for close to neutral stratification. The normalized standard deviations for humidity and CO concentration exhibit scaling similar to the wind components in the unstable regime and remain constant in the stable domain. The results for the wind components and for temperature are in the range of various functions found in other studies. The absolute values for humidity and CO concentration seem to be slightly higher, but only single examples of such investigations can be found in the literature. [ABSTRACT FROM AUTHOR]

The aim of this study is to analyse the influence of atmospheric circulation over Central Europe on the long-term variability of relative sunshine duration (RSD) and air temperature in Poland. The analysis of data from 23 stations located in different parts of the country has made it possible to indicate to what extent the trends of these two climate elements are related to atmospheric circulation and whether they occur throughout the year or only in certain months. To this end, the author's own classification of circulation types was used, which relies on a set of indices related to the velocity and direction of geostrophic flow, as well as total shear vorticity, calculated using a gridded data set of sea-level pressures. The results of the research showed that atmospheric circulation over Central Europe has a significant impact on RSD and air temperature in Poland, but not on their upward trends in recent decades. The increase in the average annual values of both these climate elements was marked in almost every circulation type. This contradicts the assumption of classical synoptic climatology, which assumes that circulation types themselves are usually considered to be constant, i.e. that changes in air temperature can be related only to an increase or decrease in the incidence of the circulation types. • Atmospheric circulation has a significant impact on sunshine duration and air temperature in Poland • There was no relationship between the atmospheric circulation over Central Europe and the upward trends of these two elements • The increase in sunshine duration and air temperature was marked in almost every circulation type [ABSTRACT FROM AUTHOR]

Climate change affects many elements of the natural environment and strongly influences the hydrology of rivers. In this study, we investigated trends in temperature, precipitation, and the water level characteristics in the small lowland river Lebiedzianka in northeastern Poland for the 50 year long period of observations (1970–2019). We recorded significant increase in air temperature and potential evapotranspiration, but the annual sum of precipitation did not change. We found significant downward trends for annual runoff. The results show a steady decrease in the number of days with high water levels. These changes caused by global warming will have a strong impact on forest habitats associated with high water levels and periodic inundations. In Europe, many of these precious habitats are protected under the Natura 2000 network as sites of high heritage value; nevertheless, their sustainability will be at risk due to the ongoing changes in their hydrological regime. [ABSTRACT FROM AUTHOR]

The identification of changes in the ice phenomena (IP) in rivers is a significant element of analyses of hydrological regime features, of the risk of occurrence of ice jam floods, and of the ecological effects of river icing (RI). The research here conducted aimed to estimate the temporal and spatial changes in the IP in a lowland river in the temperate climate (the Noteć River, Poland, Central Europe), depending on air temperature (TA) and water temperature (TW) during the multi-annual period of 1987–2013. Analyses were performed of IP change trends in three RI phases: freezing, when there appears stranded ice (SI), frazil ice (FI), or stranded ice with frazil ice (SI–FI); the phase of stable ice cover (IC) and floating ice (FoI); and the phase of stranded ice with floating ice (SI–FoI), frazil ice with floating ice (FI–FoI), and ice jams (IJs). Estimation of changes in IP in connection with TA and TW made use of the regression model for count data with a negative binomial distribution and of the zero-inflated negative binomial model. The analysis of the multi-annual change tendency of TA and TW utilized a non-parametric Mann–Kendall test for detecting monotonic trends with Yue–Pilon correction (MK–YP). Between two and seven types of IP were registered at individual water gauges, while differences were simultaneously demonstrated in their change trends over the researched period. The use of the Vuong test confirmed the greater effectiveness of estimates for the zero-inflated model than for the temporal trend model, thanks to which an increase in the probability of occurrence of the SI phenomenon in the immediate future was determined; this, together with FI, was found to be the most frequently occurring IP in rivers in the temperate climate. The models confirmed that TA is the best estimator for the evaluation of trends of the occurrence of IC. It was shown that the predictive strength of models increases when thermal conditions are taken into consideration, but it is not always statistically significant. In all probability, this points to the impact of local factors (changes in bed and valley morphology and anthropogenic pressure) that are active regardless of thermal conditions and modify the features of the thermal-ice regime of rivers at specific spatial locations. The results of research confirm the effectiveness of compilating a few models for the estimation of the dependence of IP trends on air and water temperature in a river. [ABSTRACT FROM AUTHOR]