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In the changing climate, exceptionally warm (EWMs) and dry spring months are increasingly observed. At the same time, exceptionally cold months (ECMs) are less frequent, although their impact on a warming climate becomes significant. Due to the role that such climatic anomalies play in the environment and their effects on human activity, it is very important to explain the causes of their occurrence. For this reason, in this study, the authors have attempted to determine the circulation conditions favourable to the occurrence of extremely cold (ECM) and warm (EWM) spring months in Kraków in the years 1874–2022. The study used the average temperature of individual spring months (March–May), as well as types of atmospheric circulation and air masses from the daily Calendar of Atmospheric Circulation Types for southern Poland. A distinct increase in spring air temperature (0.181 °C/10 years) and its individual months (0.162–0.191 °C/10 years) was confirmed. It was accompanied by a significant increase in the occurrence of EWM and a decrease in ECM. It was also found that the direction of air advection and the related temperature characteristics of air masses have the greatest impact on the occurrence of exceptionally cold or warm months. A slight positive effect of zonal circulation on the temperature increase at the beginning of the spring season and the advection of air from the south in April and east in May was found. In the case of the coldest months (ECMs), low temperatures most often developed in the presence of advection from the NW-N-NE directions. [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]

Contemporary climate warming is a key problem faced not only by scientists, but also all by humanity because, as is shown by the experience of recent years, it has multiple environmental, economic and biometeorological implications. In this paper, the authors identify the magnitude of annual and seasonal temperature changes in Europe and its immediate surroundings on the basis of data from 210 weather stations from 1951 to 2020. An analysis of temperatures in the 70-year period shows that air temperature has continued to grow linearly in Europe since 1985. The rate of temperature rise in three seasons of the year, namely winter, spring and summer, does not differ greatly. The highest growth over the 1985–2020 timespan was recorded in spring and the lowest in autumn—0.061 °C/year and 0.045 °C/year, respectively. In winter, the rise in temperature should be considered the least steady, as opposed to the summer when it displays the greatest stability. Overall, the warming intensifies towards the north-east of the continent. Such a strong gradient of change is especially perceivable in winter and spring, and is also marked in autumn. The opposite is true in summer, when it increases towards the south and south-west. [ABSTRACT FROM AUTHOR]

This study focuses on demonstrating the multiannual patterns of cyclical fluctuations of monthly and annual precipitation in the Polish Carpathian Mountains and their foreland. The study is based on secular series of precipitation totals from 18 meteorological stations for the 138-year period from 1881 to 2018. Use is made of Fourier analysis (FFT) and wavelet transform nonlinear estimation. The study has found a 35-year Brückner cycle in annual precipitation across the area. The number of days during the year with the types of cyclonic circulation that lead to extremely high precipitation, i.e. with the northerly and north-easterly (Nc + NEc) types and a cyclonic trough (Bc), is not clearly correlated with the 35-year harmonic variability derived from annual precipitation totals. However, the Fourier transform demonstrates a local maximum at T = 35 years. A harmonic 6-month cycle has been discovered as the only harmonic cycle in monthly precipitation. Its stability over the 138-year timespan is investigated. [ABSTRACT FROM AUTHOR]

Extreme climatic phenomena include prolonged heavy precipitation as well as long-lasting absence thereof. They are a consequence of weather anomalies and have many dangerous effects such as floods and droughts. This study aims to characterise the annual and long-term variability of the highest (Pmax) and lowest (Pmin) monthly precipitation totals and their relationship with atmospheric circulation. To achieve the above, use is made of 14 secular series (1881–2018) of precipitation from the Polish Carpathians and the calendar of circulation types over southern Poland prepared by T. Niedźwiedź (1981, 2019). On account of the variation in their relief, the Polish Carpathians are an area with a very great temporal and spatial variability in precipitation, ranging from complete absence to 500 mm per month. Pmax demonstrates a more noticeable annual frequency pattern, with a predominance in summer months, while Pmin shows smaller variations in individual months. Both Pmax and Pmin are characterised by irregular fluctuations in precipitation totals, with no statistically significant trend in their changes, which reflects the absence of a trend as regards overall precipitation volumes in this area. The study confirms an influence of the direction of air mass advection and (anti)cyclonicity of flow on Pmax and Pmin. [ABSTRACT FROM AUTHOR]

Investigation of extreme thermal conditions is important from the perspective of global warming. Therefore, this study has been undertaken in order to determine the frequency, timing and spatial extent of extremely cold months in winter time at 60 weather stations across Europe over a sixty-year period from 1951 to 2010. Extremely cold months (ECMs) are defined as months in which the average air temperature is lower than the corresponding multi-annual average by at least 2 standard deviations. Half of all the ECMs occurred in the years 1951-1970 (33 out of 67). The lowest number of ECMs was recorded in the decade 1991-2000, but since the beginning of the 21st century, their density and territorial extent has started to increase again. The extremely cold months with ECMs of the greatest spatial extent, covering at least one third of the stations (over 20 stations), included: February 1954 (22), February 1956 (36), January 1963 (25), and January 1987 (23 stations). [ABSTRACT FROM AUTHOR]

The paper addresses the frequency, amount and geographic coverage of anomalously heavy precipitation in southern Poland in relation to atmospheric circulation at the monthly and seasonal scales between 1881 and 2010. The Carpathian Mountains and their foreland were selected for the study as an area known for its high precipitation totals and frequent precipitation-triggered natural disasters, such as floods and landslides. Records from 18 stations were used to identify anomalously heavy precipitation (AHP) defined for the purposes of the study, as the top quartile ( Q ) plus 1.5 times the interquartile gap (H) of the precipitation total ( P ≥ Q + 1.5 H). The study found that most cases of AHP were recorded at one single station each. This suggests that, in addition, to the influence of circulation, local factors also play a major role in the formation of particularly heavy precipitation. The greatest absolute anomalously high precipitation totals were recorded in two disparate parts of the study area: (i) its western part exposed to wet air masses from over the Atlantic Ocean brought in by the dominant western circulation in the temperate zone and (ii) elevated parts of its south-eastern part. Two months with AHP (AHP months) occurred over the entire area (18 stations) in May 1940 and 2010. The latter case had both the greatest absolute totals (over 500 mm) and relative totals defined as their ratio to the long-term average (500 %), and it triggered a catastrophic flood in the Upper Vistula basin. [ABSTRACT FROM AUTHOR]

Extreme thermal conditions appear to occupy an important place among research subjects at a time of climate warming. This study investigates the frequency, duration and spatial extent of thermally anomalous winters in Europe during the 60 years between 1951 and 2010. Exceptionally cold winters (ECWs) and exceptionally mild winters (EMWs) were identified using the statistical criterion of plus/minus two standard deviations from the long-term winter temperature (January-December) recorded at 60 weather stations. It was demonstrated that ECWs have occurred more frequently and covered larger territories than EMWs and that they may occur anywhere in Europe, while EMWs were limited to its southern and western parts. ECWs are characterised by greater absolute temperature anomalies, as anomalies greater than |6.0 °C| account for 35 % of ECWs, but only for 8 % of EMWs. The greatest anomalies are found in the east of the continent. The largest territory affected by an ECW included 24 stations in 1962/1963, while the equivalent among the EMWs included 11 stations in 2006/2007. The study also confirmed an expected trend whereby ECWs diminished in frequency in favour of EMWs in the second half of the 60-year study period. [ABSTRACT FROM AUTHOR]

Based on the monthly precipitation series from 16 sites (in the Polish Carpathian Mountains), of 132 years' length, a relatively precise scatterplot of correlation coefficients between sites versus distance between sites is obtained. The 'rains' of Gaussian shape, in the spatial sense, are a good model, which produces a scatterplot very closely resembling the observed one. The essential parameter of the model is the area covered by the modeled rains, which results to be of order 30-50 km, though with about a twice lower value for the N-S direction. [ABSTRACT FROM AUTHOR]

The paper explores exceptional thermal conditions, an area of research that has increased in significance in the context of the changes that are being observed in climate. Specifically, the study addressed the frequency, long-term change and spatial coverage of exceptionally hot summers, and exceptionally cool summers (EHS and ECS) in Europe. The statistical criterion of plus/minus two standard deviations from the long-term average was used to identify EHS and ECS at 60 weather stations over the period 1951-2010. The study has demonstrated that EHS are characterised by greater temperature anomalies than ECS and are approximately twice as frequent. They occurred virtually everywhere within the study area, whilst ECS are concentrated in its northern part. Five EHS (1972, 2002, 2003, 2007, and 2010) and three ECS (1956, 1962, and 1976) were large enough to be recorded by at least 10% of the stations [ABSTRACT FROM AUTHOR]

The paper reports on a study of extremely cool summers (ECS), a rare but significant phenomenon responsible for various adverse economic effects. These include, in particular, effects on agriculture and the tourist industry. The seasons, their spatial extent and individual characteristics were identified in Central and Eastern Europe. The research was based on average seasonal air temperatures (June to August) and the numbers of days with maximum temperatures >25, 30 and 35 °C and minimum temperatures >20 °C, as recorded at 59 weather stations during the period 1951-2010. An ECS was defined as having an average temperature at least 2 standard deviations (t ≤ t − 2σ) lower than the average at a given station during the study period. ECS occurred at only 34 of the 59 stations (58 % of all stations), one or two per station, mainly in the northern part of the study area. Six such seasons were recorded by at least 5 % of all stations in 1962, 1969, 1976, 1978, 1984 and 1994. The average temperature of an ECS was typically 2-3 °C lower than the long-term average. While some ECSs included an extremely cool month, most such seasons (58 %) were defined by low temperatures persisting for long periods in all summer months. [ABSTRACT FROM AUTHOR]

The paper discusses the frequency, persistence and succession sequence of six types of air mass during the period 1951–2010. The study, which relied on a calendar of air masses in southern Poland published by T. Niedźwiedź, concludes that there is no simple relationship between the persistence and the frequency of specific air masses in the region. The study found that there was a great variety in the persistence of specific types of air mass and that persistence depended more on the direction of air mass advection than on their frequency of occurrence. The study also failed to identify any strict overall rule of succession, as any air mass could follow after any other, but certain finer-grained patterns emerged. In winter and summer, arctic air (A) never followed directly after tropical air (T) or vice versa. Also, the most frequent succession sequence identified was from Polar maritime fresh air (mPf) to Polar maritime old and it accounted for the vast majority of successions from mPf into any other air mass (63 % annually and 76 % in summer). [ABSTRACT FROM AUTHOR]

The paper focuses on exceptionally hot summers (EHS) as a manifestation of contemporary climate warming. The study identifies EHS occurrences in Central and Eastern Europe and describes the characteristic features of the region's thermal conditions. Average air temperatures in June, July and August were considered, as well as the number of days with maximum temperatures exceeding 25, 30 and 35 °C, and with a minimum temperature greater than >20 °C, as recorded at 59 weather stations in 1951-2010. Extremely hot summers are defined as having an average temperature equal to or greater than the long-term average plus 2 SD. A calendar of EHSs was compiled and their spatial extent identified. The region experienced 12 EHSs, which occurred in a given year at 5 % or more stations (1972, 1981, 1988, 1992, 1997, 1998, 1999, 2002, 2003, 2006, 2007 and 2010). The EHS frequency of occurrence was found to be clearly on an increase. Indeed, only one EHS occurred during the first 30 years, but these occurred five times during the last 10 years of the study period. Their geographical extent varied both in terms of location and size. EHSs were observed at 57 out of the total of 59 weather stations in the study (the exceptions were Pecora and Cluj). The average air temperature of EHSs tended to exceed the relevant long-term average by 2-4 °C. The summer of 2010 was among the hottest (temperature anomaly 5.5-6 °C) and spatially largest. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The paper discusses the impact of atmospheric circulation on the occurrence of various types of precipitation. A 146-year-long precipitation record from Kraków spanning the period 1863-2008 was used alongside a calendar prepared by Niedźwiedź (, ) describing circulation types covering the period 1873-2008 and air masses and atmospheric fronts covering the period 1951-2008 in southern Poland. The influence of atmospheric circulation on precipitation was measured using the frequency, conditional probability and average daily totals of precipitation. Circulation types, air masses and atmospheric fronts exerted influences on precipitation as a result of the seasonal variations of the thermal and moisture properties of air masses. The impact is best expressed by circulation types as these combine the aspect of cyclonicity/anticyclonicity with that of the direction of air advection, the two elements which determine the physical properties of the air. On average, liquid precipitation prevailed in all circulation types, except the Ea type in which snowfall dominated over liquid precipitation. Depending on the season, one of the three types of circulation, Wa, Wc and Bc, were shown to coincide with the greatest amount of liquid and thunderstorm precipitation. There was no single dominant circulation type for mixed precipitation or snowfall. In summer, the circulation types Nc, NEc, Cc and Bc were the most favourable to liquid and thunderstorm precipitation in terms of both probability and totals. In winter, snowfall was the most favoured by the Ec type. Frontal precipitation was twice as likely to occur as air mass precipitation, with the exception of snowfall which was predominantly an air mass type of precipitation in terms of probability, but its greatest totals were recorded on atmospheric fronts. [ABSTRACT FROM AUTHOR]