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The present study concerns the determination of the characteristics of bioclimatic conditions, as well as the synoptic situations related to the occurrence of thermal stress conditions, in Poland. The study was based on daily data obtained from the Institute of Meteorology and Water Management – National Research Institute from the period 1966–2020 for 37 synoptic stations in Poland. Based on the obtained data, values of the Universal Thermal Climate Index (UTCI) were calculated. The occurrence of heat stress increases from the north to the south, corresponding with the variability of influx of solar radiation, and is modified by factors at a smaller spatial scale. The results of this paper evidently point to the cooling effect of the waters of the Baltic Sea. In circulation conditions favouring strong and very strong heat stress, e.g. in two of the designated circulation types (T1 and T2), the occurrence of an expansive high-pressure ridge in the Atlantic-European area is typical, stretching from the region of the Azores High towards the north-east, with a secondary high developed within its boundaries. In the third of the designated circulation types (T3), the high-pressure area extends from the Azores eastwards, reaching the Black Sea. Each of the three circulation patterns associated with the unfavourable biometeorological conditions of very strong and extreme cold stress in Poland is characterised by strong pressure centres formed in the Euroatlantic region, triggering the airflow from the northern (T4) or eastern (T5, T6) sector. [ABSTRACT FROM AUTHOR]

The primary objective of the paper was the determination of the atmospheric circulation favouring the occurrence of strong and very strong stress of the human organism due to heat stress in Poland. The paper was prepared based on data obtained from the Institute of Meteorology and Water Management – National Research Institute and the National Center for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). The criterion of extreme stress of the human organism adopted in the paper covered conditions in which the Universal Thermal Climate Index (UTCI) value was higher than 32 °C. The research showed a statistically significant increase in half of the analysed stations and an increasing tendency or no changes in the remaining stations. Moreover, after 1990, conditions particularly strenuous for the organism were recorded (UTCI > 40 °C) over a major part of the territory of Poland. The occurrence of days with strong and very strong heat stress in Poland was related to the presence of high-pressure systems blocking zonal circulation. The research permitted the designation of three types in which the pressure field showed common features, but differed in the location of anticyclonic systems. [ABSTRACT FROM AUTHOR]

From the beginning of the 21st century, the heat waves in Europe have become more frequent, severe and longer lasting, especially in the southern region. The longer duration of heat waves may be partly attributed to wave‐amplification, high‐amplitude waves in the mid‐latitudes, favouring the longer‐lasting blocking systems. The primary objective of the paper was to examine the long‐term changes of hot days and heat wave events and to identify the atmospheric circulation condition that prevails its occurrence. The other object was to investigate the correlations between hot days' occurrence in Poland and sea‐ice cover and sea surface temperature changes in the Arctic and its surroundings. Over the past few decades, Central and Southern Poland have experienced a considerable rise in maximum temperatures, which has led to an increase in the number of hot days. This increase is particularly prominent during the summer months (June, July and August) but also in May and September, which extends the hot season. Although heat waves have become more frequent and persistent since 2006, their mean intensity has remained unchanged. During all heat waves in Poland, the high‐pressure centre was located over the country or its close neighbourhood, mainly in the eastern sector but also in the south, southwest or over Scandinavia. The blocking systems were mainly related to the extended ridge of the Azores High, but also to strong blocking over the North Pole and Greenland reaching Scandinavia or anomalous high pressure in the East Arctic. The longest‐lasting heat waves were usually preceded by air masses advection from the Atlantic, but the highest potential temperature along the trajectories was observed for the southern direction of inflow. The growing number of hot days is statistically significantly related to the decreasing sea‐ice cover and increasing sea surface temperature in Arctic and Subarctic regions. [ABSTRACT FROM AUTHOR]

The paper aims to analyse the relationship between the amount of global solar radiation (GSR) reaching the Earth's surface in Poland and the direction of air mass advection, using 72-h backward trajectories (1986–2015). The study determined average daily sums of GSR related to groups of trajectories with certain similarities in shape. It was found that the average daily sums of GSR during air mass inflow from all the directions (clusters) identified were significantly different from the average daily sum in the multi-year period. A significant increase in the amount of GSR over Poland is accompanied by air mass inflow from the north and east. The frequency of these advection directions is 27% of all days. The western directions of advection prompt different GSR sums: from slightly increased during advection from the north-west, to significantly decreased during advection from the west (from the central and western part of the North Atlantic). Special attention was given to days with extremely large (above the 0.95 percentile) and with the largest (above the 0.99 percentile) GSR sums. These are prompted by two main types of synoptic conditions: the Azores High ridge covering Central and Southern Europe; and the high-pressure areas which appear in Northern and Central Europe. [ABSTRACT FROM AUTHOR]

Mountains are one of the most sensitive regions in terms of climate changes. This also concerns water balance, which plays an important role, especially in the context of the ecological state. Furthermore, numerous studies indicate the atmospheric circulation as one of the crucial factors affecting climate conditions. Therefore, the goal of the paper is to examine the impact of the atmospheric circulation on the changes in climate water balance (CWB) in the Sudetes Mountains and their foreland. The analysis was carried out based on the 1981–2020 data derived from the Polish and Czech meteorological stations. The impact of the circulation factor was examined using the Lityński classification, while the calculation of evapotranspiration based on the Penman–Monteith equation. The results showed that despite positive trends for evapotranspiration, the changes in CWB in 1981–2020 were generally statistically insignificant. The only exception was the increase in CWB under the eastern circulation and its negative tendency for the western and southern sectors for some of the stations. This corresponds to the changes in the frequency of the circulation types. The results of the study can be used in further research on water balance in the region. [ABSTRACT FROM AUTHOR]

The key factor that affects the inflow of radiant energy to the Earth's surface is the circulation of the atmosphere (caused by uneven distribution of air pressure on the globe) and the related changes in the amount of aerosols and cloudiness. This paper identified the areas in the Euro‐Atlantic region where the air pressure change had a significant impact on global solar radiation (GSR) changes over Poland, during the period 1986–2015. In general, growing GSR sums over Poland are to some extent related to the positive phase of the NAO (simultaneous pressure growth in the area of the Azores High and the pressure decrease in the area of the Icelandic Low). Correlation coefficient between the NAO index and GSR over Poland equals 0.18 (statistically significant at α = 0.05). In turn, in summer and autumn the pressure growth in southern Scandinavia results in a significant increase in the amount of GSR over Poland. Days with extremely large GSR sums (above the 95th percentile) are also prompted by the Azores High ridge which covers Central and Southern Europe, and by air mass inflow from the Atlantic. [ABSTRACT FROM AUTHOR]

Copyright of Polish Geographical Review / Przegląd Geograficzny is the property of Polska Akademia Nauk, Instytut Geografii i Przestrzennego Zagospodarowania and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

The paper characterises the annual pattern and the long-term variability of the Tourism Climate Index (TCI) in Toruń in the years 1966-2020. In the annual variation, conditions for tourism and recreation were best from May to August. For the summer period (from June to August), the climatic conditions according to TCI were excellent, while for May they were assessed as very good. Meanwhile, the least favourable conditions for recreational and tourist activity occur in the winter months of January and December. In Toruń, there was a statistically significant increase of 0.9 pt/10yr in the annual average TCI value. An improvement in climatic conditions for humans was demonstrated for all seasons but was greatest in spring and autumn (respectively 1.6 and 1.0 TCI pt/10yr). Atmospheric circulation was also found to affect TCI. This was determined using a calendar of circulation types over central Poland, based on which indices of zonal, meridional and cyclonic circulation were used. The study has shown that anticyclonic circulation has the greatest impact on improving conditions for tourism. [ABSTRACT FROM AUTHOR]

The paper discusses the impact of atmospheric circulation on the occurrence of droughts. The research includes mean monthly discharges for 7 rivers in 1954–2018. Dry periods were determined with Standardised Streamflow Indices (SSI-12). Additionally, the circulation type calendar for Central Poland was used to determine the atmospheric circulation indices: western zonal (W), southern meridional (S) and cyclonicity (C). The analyses indicated a variation in the duration and intensity of droughts in the rivers. 2014–2017 was the driest period with the lowest SSI-12 for most rivers and the highest number of extremely dry months. The advection of air from the West and the South prevailed and anticyclonic synoptic situations dominated over the cyclonic types. Drought spells occurred at a dominance of anticyclonic circulation, with the inflow of air from the North and with increased western zonal circulation. [ABSTRACT FROM AUTHOR]

The paper discusses the circulation and thermal conditions over Poland and their dependence on the sign and values of the North Atlantic Oscillation (NAO) index (hereinafter NAO+ and NAO-). The input data used in the research consisted of average monthly values of air temperature in Warsaw, NAO index values, and a calendar of atmospheric circulation types according to Lityński (1969). The study comprised the three winter months (December, January,February) from the period 1951-2015. The dependence between the circulatory and thermal conditions was investigated on the basis of 10 months representing each of the winter months with the highest NAO+ and NAOvalues and 10 months with the greatest positive and negative temperature deviations from the long-term average (Δt+, Δt-), based on the assumption, that they should largely be the same months. In general, the analysis confirmed these assumptions, but it also showed that there are deviations from previously known regularities as regards the effect of the positive or negative phases of the NAO on the thermal conditions in Poland. [ABSTRACT FROM AUTHOR]

The primary objective of this paper was to determine the circulation conditions of the occurrence of cold spells in Poland and Germany. The observed inconsiderable warming slightly contributed to a change in the number of cold days and cold spells. The occurrence of cold spells in Poland and Germany was related to considerably more active and intensive pressure systems than on average in the winter season in the studied years. A strong high pressure system was located over much of the continent, blocking westerly circulation. During the occurrence of cold spells, negative anomalies of isobaric surface heights were recorded with the greatest anomalies being in the 300–250 hPa heights. The highest air temperature anomalies were recorded on the lowest isobaric levels, where they amounted to <−10°C. On average, anomalies on the 300 hPa isobaric level began developing approximately 9 days before the beginning of cold spells over the study area. The decay of cold spells was not related to rapid exchange of air masses, but rather to gradual weakening of anomalies in the upper troposphere, and their shifting westwards. [ABSTRACT FROM AUTHOR]

This paper aims at recognizing spatial differentiation in probability of ice days occurrence with reference to atmospheric circulation, using regional classification of circulation types for Poland. Daily maximum air temperatures measured at nine meteorological stations were used to recognize the ice days occurrence in the period from January 1951 to March 2014. The relations between the ice days occurrence and atmospheric circulation were analysed using catalogues of circulation types compiled for nine grid boxes within Poland. Linkage between the frequency of ice days and atmospheric circulation was recognized in the period of January 2001 - March 2014. A decreasing tendency in the frequency of the occurrence of winter ice days was found. The occurrence of ice days in Poland is clearly related to atmospheric circulation. In the entire area of Poland their occurrence is favoured by eastern and south-eastern advection of air during anticyclonic conditions (types Ea nad SEa). Regional variability is also noticeable. [ABSTRACT FROM AUTHOR]

This paper concerns the relationships between selected circulation indices and air temperature over Southeast Poland between 1871-2010. The geostrophic wind speed and the resultant vorticity were computed based on daily gridded fields of mean sea-level pressure over an area defined from 5°20' to 40°20'E and from 41°15' to 61°15'N. The highest daily mean geostrophic wind speed over Southeast Poland is observed from December to February. In turn, the maximum (positive) values of the resultant vorticity occur in April and May, while the minimum (negative) values are observed in January. Mean air temperature from November to February has a strong positive correlation with the geostrophic wind speed. Moreover, the occurrence of the highest coefficients regarding the correlation between the geostrophic wind speed and air temperature in winter as well as the NAO index was recorded at the beginning of the 21st century. This suggests that the range of impact of sea-level pressure distribution over the North Atlantic on the winter air temperature over Southeast Poland may have increased over the last decades. One of the causes may be an eastward shift of the position of the center of the Icelandic Low and the Azores High in the period from December to February. [ABSTRACT FROM AUTHOR]

The aim of this study is to present the spatial and temporal variability of the frequency of dry and wet days and dry and wet spells against the background of changes in precipitation and atmospheric circulation. The study is based on daily precipitation totals from 46 meteorological stations in Poland from 1966 to 2023. Additionally, seven circulation indices were used, namely GBI, NAO, AO, EA, EA/WR, SCAND, and AMO. Dry days are defined as days without precipitation. Wet days are days with at least 1 mm of precipitation. It was shown that dry spells are much more common than wet spells, are longer, and cover larger areas. Long-term changes in the annual characteristics of dry and wet days and spells are not statistically significant. Only the length of the most extended dry spell in the year increases. However, there are significant changes in their annual cycles. Spring is drier; in summer, precipitation decreases in the south and increases in the north; November and December, symbols of gloomy rainy weather, are increasingly drier; and rainy weather has shifted to January and February. The impact of circulation varies according to the season, with the NAO, AO, SCAND, and GBI indices having the greatest influence. [ABSTRACT FROM AUTHOR]

A 117 year series of hourly precipitation data from Kraków, South Poland and the Niedźwiedź classification of synoptic weather types were the basis of a detailed study of diurnal precipitation variation and atmospheric circulation types. The analysis of the relationship between precipitation and circulation types was restricted to the warm half of the year (May–October). During this period precipitation ispredominantly liquid. This paper discusses the role of theCarpathian orographic barrier in the development of the 24 hour precipitation pattern. The diurnal cycle of precipitation shows a stronger relationship with the direction of air mass advection than with pressure system type. Circulation types linked with cold and moist air mass advection cause a more uniform precipitation variation. Conversely, diurnal precipitation patterns in circulation types bringing continental Polar air are affected to a greater extent by thermal than dynamic factors. This influence is manifest by a greater amplitude of the diurnal cycle of precipitation frequency. [ABSTRACT FROM AUTHOR]

This paper presents the application of the high-resolution WRF model data for the automatic classification of the atmospheric circulation types and the evaluation of the model results for daily rainfall and air temperatures. The WRF model evaluation is performed by comparison with measurements and gridded data (E-OBS). The study is focused on the area of Poland and covers the 1981-2010 period, for which the WRF model has been run using three nested domains with spatial resolution of 45 km × 45 km, 15 km × 15 km and 5 km × 5 km. For the model evaluation, we have used the data from the innermost domain, and data from the second domain were used for circulation typology. According to the circulation type analysis, the anticyclonic types (AAD and AAW) are the most frequent. The WRF model is able to reproduce the daily air temperatures and the error statistics are better, compared with the interpolation-based gridded dataset. The high-resolution WRF model shows a higher spatial variability of both air temperature and rainfall, compared with the E-OBS dataset. For the rainfall, the WRF model, in general, overestimates the measured values. The model performance shows a seasonal pattern and is also dependent on the atmospheric circulation type, especially for daily rainfall. [ABSTRACT FROM AUTHOR]

This paper investigates fog frequency in southern Poland in relation to various topography (concave and convex forms) and atmospheric circulation types. It also discusses long-term variability in the annual and seasonal number of days with fog. Daily information on fog occurrence was taken from three high quality synoptic stations representing various landforms: Kraków-Balice (bottom of the hollow), Katowice-Muchowiec (Silesian Upland) and Bielsko-Aleksandrowice (summit of Carpathian Foothill). In the central part of southern Poland during the last 50 years (1966-2015) fog occurred on average during 53-67 days a year. The annual number of foggy days in Kraków (67 days) located in a structural basin was by 14-15 days higher than in Bielsko (53 days) situated in the Silesian Foothills. In the annual course, high fog occurrence (above 6 days per month) was observed from September to January, with the maximum in Kraków (10 days in October). At every station the monthly minimum of fog occurrence fell in July (2 days). In summer and spring the highest probability of fog occurrence was found on days with anticyclonic types and air advection from the northeastern (Na, NEa) and eastern (Ea, SEa) sectors. In autumn, a high probability was also found for the anticyclonic types with advection of air mass from the eastern and southern sectors. In the Carpathian Foothills (Bielsko) the probability of fog occurrence in winter was significantly enhanced only for the cyclonic types with air advection from the eastern sector (NEc, Ec, SEc) and nonadvective types Cc (cyclone centre) and Bc (cyclonic trough). Trends in the fog frequency were mostly insignificant. The only significant decreasing trend was found in Kraków on the annual scale and in summer when fog frequency was low. [ABSTRACT FROM AUTHOR]

Land-sea interaction at the Polish Baltic Coast impacts the specific local climate conditions. Thermally driven circulation, observed mainly in the summer season, causes the advection of the cool sea air over land and influences the local atmospheric environment, including bioclimatic conditions. The aim of this paper is to present the evaluation of the WRF model for forecasting sensitive bioclimatic conditions on a selected day with sea breeze in the vicinity of the Łeba Sandbar (the Słowiński National Park). The results obtained from a numerical weather prediction model were post-processed to calculate the daily variability of two biothermal indices: the Effective Temperature (ET) and the Dry Cooling Power (H). To evaluate the thermal comfort of a person wearing typical clothes, the Michajlow's, Petrovič and Kacvińsky's scales were adopted. A detailed analysis performed for 31st July 2010 shows in most cases a satisfactory level of agreement between the simulated data and the in-situ measurements for nested domains with horizontal grid resolution less than 2 km. However, the simulation results tend to underestimate the thermal comfort, especially in the middle part of the Łeba Sandbar due to terrain data misrepresentations, which results in the overestimation of wind speed. [ABSTRACT FROM AUTHOR]

Copyright of Prace Geograficzne is the property of Jagiellonian University, Institute of Geography & Spatial Management and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Abstract: The paper presents parameters of the diurnal rainfall cycle for rainfall equal or exceeding 2.5mmh−1 during both the summer and winter halves of the year. It then discusses the impact of various circulation systems on the distribution of the frequency of rainfall occurrence during a 24-hday in the summer half of the year. The results of these investigations contribute to a greater understanding of the atmospheric processes associated with heavy precipitation and may be used to improve the forecasting of the temporal distribution of short-duration convective precipitation. A pattern with a single heavy rainfall maximum was identified. A variety of diurnal patterns of amplitude and time of maximum rainfall emerged depending on the atmospheric circulation determining the thermal and humidity properties of air masses. The paper was based on hourly rainfall records in Kraków and on a daily catalogue of atmospheric circulation types in southern Poland spanning the period 1886–2007. [Copyright &y& Elsevier]

This paper investigates the relationship between maximum precipitation in Krakow and types of atmospheric circulation in southern Poland, as classified by Niedźwiedź. Three characteristics were used to define this relationship: maximum precipitation (Pmax), its duration (d) and probability of exceedance (p). The input data came from Kraków's uniquely long and homogenous pluviographic record spanning the period 1886-2007. Hourly precipitation values for the maximum precipitation events were identified and arranged in 1-24 hour intervals. They were then processed using the generalized extreme value (GEV) distribution to produce quantiles of maximum precipitation totals in each of the intervals and broken down by the corresponding circulation type. Differences between the development mechanisms are manifested in relationships between precipitation characteristics and their measure of randomness, i.e. exceedance probability. This paper demonstrates that maximum precipitation events depend on their duration d and atmospheric circulation. The maximum short-duration (one-hour) events occur primarily in either of two circulation types: (i) cyclonic with advection from the east and from the southeast or (ii) low-pressure centre and cyclonic trough. Maximum long-duration precipitation events (24 hour), on the other hand, occur in the cyclonic type of circulation with advection from the north and from the northeast. [ABSTRACT FROM AUTHOR]

This paper is devoted to the synoptic-climatic analysis with the application of circulation types and Geographic Information Systems (GIS). Construction of daily climatic air temperature maps for the Polish territory was the main aim of the work. Analysis was based on the mean daily temperature data from all synoptic and some climatological stations (73 stations totally) for the 50-year period of 1951-2000. The synoptic-climatic analysis was done using a well known circulation calendar developed by the German Meteorological Service 'Grosswetterlagen'. Residual kriging was chosen for the map constructions. Several geographic parameters, including elevation, latitude, longitude, and distance to the Baltic coast, were used as predictor variables for air temperature. However, the particular circulation type was the crucial predictor. Maps were created for all months for the Grosswetterlagen circulation types, which occurred more than 30 times during 1951-2000. Special attention was paid to the extreme thermal months of January and July. Maps constructed in the way described confirmed that application of circulation types was quite a good tool for improving accuracy of thermal daily maps. Accuracy was much higher for most of the maps constructed for particular circulation types than for the maps created without application of circulation types. There was only one exception: non-advective anticyclonic types during winter time. Then, relatively large variability of the temperature can be observed in the concave landforms and the constructed maps have only approximate meaning. Copyright © 2006 Royal Meteorological Society. [ABSTRACT FROM AUTHOR]

The study objective was to characterise biometeorological conditions during the long May weekend (1–3 May) in Poland in the period 1966–2020 and determine baric conditions causing their variability. The conducted research employed data such as air temperature, relative humidity, wind speed, and total cloudiness. The aforementioned data were collected at 12:00 UTC. In the first year of the conducted study, the Universal Thermal Climate Index (UTCI) was calculated for the period of 1–3 May in the years 1966–2020. Next, circulation conditions were analysed in the designated groups based on daily sea level atmospheric pressure values and isobaric surface height of 500 hPa. This study evidenced the occurrence of variable biometeorological conditions during the long May weekend in Poland. The lowest index values were recorded at the coast of the Baltic Sea and in Northeast Poland, and the highest in the southern and western regions. On the analysed days of May in the years 1966–2020, days classified as days with no thermal stress were recorded the most frequently, followed by days with cold stress, and days with warm stress that occurred sporadically. People planning tourist activity on the analysed days should be prepared for diverse biometeorological conditions, from those causing cold stress to those causing heat stress. [ABSTRACT FROM AUTHOR]

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]

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]

Copyright of Polish Geographical Review / Przegląd Geograficzny is the property of Polska Akademia Nauk, Instytut Geografii i Przestrzennego Zagospodarowania and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The paper identifies relationships between lake water levels and indices of macroscale atmospheric circulations: Arctic Oscillation (AO), North Atlantic Oscillation (NAO), East Atlantic (EA), and Scandinavian pattern (SCAND). Correlation coefficients between synchronous and asynchronous series of monthly water levels and 4 circulation indices were calculated. Based on Ward hierarchical grouping considering 156 correlation coefficients, the groups of lakes were designated due to the strength and term of relation of circulation indices with lake water levels. It was found that these links are not strong but noticeable. The strength of relationships varies in space and time, and the designated groups of lakes refer not only to the climatic diversity of the studied area, but also to some extent to the types of water levels regime. The observed relationships are the most important in the case of AO and NAO (particularly in winter period), and slightly weaker for EA and SCAND. The analysis used mean monthly water levels of 15 lakes in northern Poland from 1976–2015. [ABSTRACT FROM AUTHOR]

Abstract: The paper proposes a classification of deep cyclones determining the weather in Poland grouped according to their track. The study used data from NCEP/NCAR reanalysis spanning the period 1971–2000. The analysis considered: values of 1000hPa geopotential height at 12 UTC recorded at selected grid points, maps of 1000 and 500hPa geopotential height and maps of sea-level air-pressure field at 12 UTC. Seven groups of deep cyclones were identified. The dominant groups involved cyclones originating over the North Atlantic and crossing over Iceland (T2=29.3%), and those moving from west to east, typically over the British Isles (T3=26.8%). Other large groups of cyclones involved systems travelling from the Mediterranean towards north-eastern Europe (T7=10.5%), and those moving from the Norwegian Sea though the Baltic Sea into northern and north-eastern Europe (T1=8.4%). Cyclones, with air pressure ranging from 940 to 1000hPa, were found to have different levels of influence depending on the region. Most of the systems were recorded between October and March (86.4%), but isolated cases were also observed in summer. No statistically significant long-term trends in their occurrence were identified. [Copyright &y& Elsevier]

Abstract: The paper focuses on synoptic and climate analysis with the application of circulation types based on six classification schemes, both subjective and objective. The principal goal of the study was to determine circulation types with respect to the occurrence of extreme values of air temperature. A comparison between different available classifications was also performed. Maximum and minimum daily temperatures for the 56-year study period (1951–2006) were used in the analysis. The necessary data series were obtained from 61 weather stations, relatively well spaced across Poland. Each series was checked for homogeneity and evaluated. Detailed calculations were performed for the summer (June–August) and winter (December–February) seasons. Extreme values were selected with respect to probability distribution bases. The top and bottom 5% were used for further analysis. Calculations of extreme values for particular types and classifications were the main phase of analysis. All extreme temperature values were analyzed for each type. This enabled the creation of histograms presenting types producing the highest number of particular extremes. The study showed that circulation types with an anticyclonic ridge were the most important for extremely hot days in the summer, while extremely low temperatures in the winter were usually associated with anticyclonic types with an easterly airflow. A special effort was made to identify the classification scheme yielding the best accuracy in evaluating extremes. [Copyright &y& Elsevier]

The main aim of this study was to present thunderstorms' occurrence in Poland in the 20th century. The paper also attempts to assess the impact of atmospheric circulation on the variability of number of days with thunderstorms and estimate synoptic conditions conducive to the formation of thunderstorms. The analysis was based on thunderstorm observations from 56 synoptic stations in Poland in the period 1951–2000 and 7 stations for the years 1885–2000. In the second part of the study, the types of synoptic situations elaborated by Osuchowska-Klein, the types of synoptic situations by T. Niedz´wiedz´, indices of atmospheric circulation by Z. Ustrnul and index of North-Atlantic Oscillation (NAO).As a result, it was determined that during the analysed period, no tendency was found in the multi-annual course of mean yearly number of days with thunderstorms in Poland, and the values usually do not differ much from the value typical for the climatic–geographical region in which Poland is situated. Synoptic situations have less influence on thunderstorm occurrence than that usually suspected. The eastern advection has the largest influence on the occurrence of the days with thunderstorms, especially in southern Poland. The analysis of relations between the variability of number of days with thunderstorms and the changes of the circulation indices proved these regularities. [Copyright &y& Elsevier]

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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]

The main purpose of the research was to determine the conditions affecting ice phenomena, including the three-phase cycle of ice: expansion, retention and decay of the ice cover on selected rivers of the Baltic coastal zone in the Northern Poland (Przymorze region). The analysis has been elaborated for the years 1951–2010 against the backdrop of currently occurring climatic changes, with particular emphasis on the development and phase variability of the NAO. The article presents the impact of the variability in atmospheric circulation which has manifested in an increase in air temperature, over the last 20 years, on thermal conditions during winter periods in the South Baltic Coastal Strip. The increase in air temperature has contributed to an increase in the temperature of river waters, thus leading to a shortening of the duration of ice phenomena on rivers in the Przymorze region. The article also brings to light an increased occurrence of winter seasons classified as cool, and a disruption in the occurrence of periods classified as normal over the last 30 observed years. The research has demonstrated a significant dependence between the seasonal change in air temperature and the variability of thermal conditions of water, which has a direct impact on the variability of the icing cycle of rivers in the Przymorze region. The authors also show that the variability in forms of ice phenomena for individual river sections is determined by the local factors, i.e. anthropogenic activity, impact of urbanized areas or inflow of pollutants. [ABSTRACT FROM AUTHOR]

Occurrence of heat and cold waves in Poland in the years 1966–2015 (1966/1967–2015/2016) was described, and their circulation conditions were determined in this study. A heat wave is defined as a period of at least 3 days with Tmax > 30.0 °C and a cold wave as a period of at least 3 days with Tmax <− 10.0 °C. Heat waves occurred most often in central and southern Poland and cold waves in north-eastern Poland. The occurrence of both heat and cold waves is related to high pressure systems. Anticyclonic blocking patterns both in winter and summer inhibit the zonal flow of air masses and intensify the meridional flow. Positive sea level pressure anomalies occurred over the study area, in the case of heat waves up to 3 hPa and in the case of cold waves up to 11 hPa. Perpendicular profiles showing geopotential height and air temperature anomalies in the troposphere were identified for the selected cases of extreme temperature episodes. Centres of geopotential height positive/negative anomalies were detected at the level of 300–250 hPa geopotential height, right over the area of the positive/negative surface temperature extremes. [ABSTRACT FROM AUTHOR]

Sunshine duration analysis was based on a series of measurements spanning the period from 1901 to 2014 for Śnieżka (1603 m a.s.l.) and from 1961 to 2000 for Szrenica (1362 m a.s.l.). The average annual sunshine duration (SD) on Śnieżka is 1423.0 h, which is among the lowest values in Poland. On average, the main ridge of the Karkonosze range receives 31% of potential sunshine duration in annual terms: from 25% in December to 36% in August and May. The changes in sunshine duration recorded on Śnieżka point to the existence of two cycles: a short one of approx. 2–4 years and a long one of approx. 60 years. The former most probably reflects the rhythm of atmospheric circulation in the North Atlantic (North Atlantic Oscillation), while the latter reflects the impact of ocean circulation associated with the AMO (Atlantic Multidecadal Oscillation) mechanism. Annual SD totals for the years 1901–2014 exhibit a slight trend to an increase of approx. 2.5 h/10 years, and the rate of increase during the winter quarter is many times higher than during the other seasons. Average monthly sunshine duration differences between Śnieżka and Szrenica are positive for all months of the year with the average monthly difference being 10 to 11 h. This means that the average radiation conditions on Śnieżka are more favourable than the main ridge of the Karkonosze range, which lies at an altitude 200 to 250 m lower. Average daily sunshine durations recorded on Śnieżka are only shorter than those on Szrenica for macro-types of atmospheric circulation with advection from the south. [ABSTRACT FROM AUTHOR]

All dunes within a dunefield usually show a similar response to the wind regime. However, in the late-Holocene coastal dunefield in NW Poland the surface topography suggests that slipface orientation may vary significantly with distance from the coast, which is rarely reported in the literature. The dunefield was stabilized with forest in the mid-19th century, preserving a unique record of atmospheric circulation in the South Baltic region at the end of the Little Ice Age. To elucidate the Holocene processes occurring along the study site a pseudo-3D GPR data set was collected. Six grids of parallel GPR lines combined with 400 m of GPR profiles (2D) were collected across the dunefield and displayed using GOCAD for interpretation and geostatistical analysis. The geophysical data revealed that the larger dunes almost entirely consist of steeply laminated facies. Most importantly the pseudo-3D data, supported by geostatistical estimates of strata dip directions, revealed the existence of three zones parallel to the coastline with the mean dip direction almost perpendicular to the coast in the northern coastal strip and almost parallel to it in the southern part. Spreads of the dip directions in pseudo-3D GPR data sets recorded on the stoss slopes of dunes and crests suggested initial deposition on transverse dunes, which later were transformed into barchanoid dunes. This can probably be linked to changes in the wind regime, i.e. reduction in velocity of the northern and northwestern winds leading to reduced sediment supply from the coast. While the data provide a new interpretation of Holocene dunefield dynamics at this site, they also suggest that the minimum number of pseudo-3D GPR grids required to establish general trends using geostatistical analysis should be at least 10, with even more data needed at larger, or more complex dunefields. [ABSTRACT FROM AUTHOR]

This study investigates atmospheric conditions' influence on the mean and extreme characteristics of PM concentrations in Poznań during the period 2006-2013. A correlation analysis was carried out to identify the most important meteorological variables influencing the seasonal dynamics of PM concentrations. The highest absolute correlation values were obtained for planetary boundary layer height ( r = −0.57), thermal (daily minimum air temperature: r = −0.51), anemological (average daily wind speed: r = −0.37), and pluvial (precipitation occurrence: r = −0.36) conditions, however the highest correlations were observed for temporal autocorrelations (1 day lag: r = 0.70). As regulated by law, extreme events were identified on the basis of daily threshold value i.e. 50 μg m. On average, annually there are approximately 71.3 days anywhere in the city when the threshold value is exceeded, 46.6 % of those occur in winter. Additionally, 83.7 % of these cases have been found to be continuous episodes of a few days, with the longest one persisting for 22 days. The analysis of the macro-scale circulation patterns led to the identification of an easy-to-perceive seasonal relations between atmospheric fields that favour the occurrence of high PM concentration, as well as synoptic situations contributing to the rapid air quality improvement. The highest PM concentrations are a clear reaction to a decrease in air temperature by over 3 °C, with simultaneous lowering of PBL height, mean wind speed (by around 1 m s) and changing dominant wind directions from western to eastern sectors. In most cases, such a situation is related to the expansion of a high pressure system over eastern Europe and weakening of the Icelandic Low. Usually, air quality conditions improve along with an intensification of westerlies associated with the occurrence of low pressure systems over western and central Europe. Opposite relations are distinguishable in summer, when air quality deterioration is related to the inflow of tropical air masses originating over the Sahara desert. [ABSTRACT FROM AUTHOR]

We present the results of research concerning the temporal and spatial variability of the dates of the onset of the growing season (OGS) in Poland using satellite data. The data from the years 2001-2010 were obtained from the MODIS Global Land Cover Dynamics Product (MCD12Q2). The study examined the relationship between the OGS dates and types of land cover, meteorological elements (air temperature and snow depth), and atmospheric circulation conditions. In the study period, the average OGS dates for the entire country showed the strongest correlation with minimum air temperature from January to March (R²=0.95). The photosynthetic activity of vegetation in early spring was also considerably influenced by the strength of zonal flow and the type of land cover. The latest OGS dates in Poland were observed in areas with a higher share of wetlands and inland waters, and the earliest ones in urban areas and agricultural land. [ABSTRACT FROM AUTHOR]

Late spring freeze events, a significant agroclimatic hazard, are investigated for Poland. Daily minimum air temperatures from 184 stations for the period 1951-2010 were used to analyze the frequency and conditional probability of late spring freezes. In addition, three classification schemes were employed to investigate the atmospheric circulation responsible for late spring freezes events. The findings suggest that knowledge of the airflow influencing late spring freezes can help to understand the complex historical trends and projected future changes in freeze risk for perennial crops [ABSTRACT FROM AUTHOR]

The seasonal stability of snow cover (ISS) was defined as a percentage ratio of the real and the potential snow cover duration in a winter season. Main results of the study are as follows: (1) alternately occurring periods of high and low values of the index of snow cover stability did not appeared simultaneously in mountainous and non-mountainous areas; (2) in the majority of Poland area both zonal and meridional components of the atmospheric circulation influence the ISS; however, in south the meridional air flow reveals the stronger impact, mostly due to the intensification of the southern advection by the foehn effect; and (3) changes of two or three indices describing atmospheric circulation explain up to 50 % of the ISS in Poland. The diminishing stability of snow cover in Poland corresponds with an increasing intensity of the advection from the western sector in winter in the second half of the twentieth century in Europe. [ABSTRACT FROM AUTHOR]

Fuzzy logic was applied as a methodology to create an objective calendar of daily atmospheric circulation based on an existing atmospheric circulation classification system for Poland called the Osuchowska-Klein method, which includes 13 circulation patterns. In this study, circulation patterns given by Osuchowska-Klein were expressed as normalized values of sea level pressure in a regular 5° × 5° grid over the area of interest. Cases of daily atmospheric circulation (i.e., normalized values for the same domain) observed from January 1948 to December 2007 were defined in the same manner. The pattern-matching procedure employed in the study was made objective with the application of fuzzy logic sets in a few steps as follows: (1) discrimination and grouping of grid points as well as their classification in order to clearly define each Osuchowska-Klein circulation pattern, (2) calculation of the similarity between observed normalized pressure and that of the pattern at each selected grid point using a membership function, (3) determination of the degree of fulfillment for every class of grid points, (4) determination of the degree of a case and pattern, (5) selection of the circulation type for a particular day based on the degree of fulfillment for each pattern. The largest value of the degree of fulfillment indicates the type of circulation pattern on any given day. Finally, a validation of the obtained results is discussed. This was accomplished using the chi-square test and a comparison of consistency between the traditional and objective approach types. The results do show some differences between the subjective and objective methods, however, they are not major differences, especially when taking into account the fact that the two methods are quite different, as well as the complex nature of pressure systems. [ABSTRACT FROM AUTHOR]

Synoptic conditions of extreme rainwater pollution episodes, evidenced by maximum values of parameters measured in the protected area of Wielkopolski National Park (western-central Poland), were analysed in this study. Precipitation samples were tested for the following parameters: pH, electrical conductivity and the concentration of the following elements: F, Cl, NO, NO, PO, SO and Na, NH, K, Mg, Ca. It was assumed, that in winter, western advection of Atlantic air masses was the most frequent aerosol and pollution transport scenario for the investigated area. In summer the most heavily pollution occur at the intensified meridional flow over the central Europe, indicating advection of cooler air from northern Europe and the North Sea. In most of cases, the weather conditions causing extreme concentration of examined pollutants, were determined by the movement of weather fronts over considerable parts of Poland and by precipitation caused by those fronts. [ABSTRACT FROM AUTHOR]

The article presents a study which analyzes the diurnal cycle of thunderstorm precipitation in Krakow, Poland from 1951-2006. It involved a study of the consistent record of pluviographic measurements from the Astronomical Observatory of the Jagiellonian University in Krakow and the collection of sea level synoptic maps. It concludes that the synoptic situations which determine the thermal and humidity properties of air masses influences the 24 hours diurnal cycle of thunderstorm precipitation.

Recent analyses have identified summer warming trends in Europe in recent decades, culminating in 2003, when mean summer temperatures were exceptionally hot over much of Europe. Mean monthly temperatures were very high in July 2003 and reached record levels in both June and August. In 2006, the mean monthly temperature for July reached a record high. Our analysis of temperature observations shows that in July 2006, as in summer 2003, maximum temperatures were more abnormal than minimum values. The 2006 heatwave was located more to the north than in 2003, and particularly affected the Netherlands, Belgium, Germany, Poland, France and Switzerland. The July 2006 anomalies were similar in magnitude to those of June and August 2003, but the discrepancy between minimum and maximum temperature anomalies was larger in 2006 compared to both June and August 2003. For maximum temperature, the affected land area by anomalies higher than 4–6 K was largest in July 2006, although the anomalies were higher in June and August 2003 at the most anomalous sites. In the north of Europe, the absolute monthly temperature values were higher in July 2006 compared to both June (also on the Iberian Peninsula) and August 2003. [ABSTRACT FROM AUTHOR]

Atmospheric drought is an extremely important issue on a global, regional and local scale, especially in the context of climate change. The aim of the study was to assess the spatiotemporal variation of atmospheric (meteorological) drought in agricultural areas of east-central Poland, represented by the Lublin Voivodeship (Lublin region) in 1971–2015. Average monthly air temperatures and monthly precipitation totals recorded over the 45-year period at 25 weather stations were used in the study. The assessment of spatiotemporal variation in atmospheric drought in the study area was based on calculations of the aridity index. The analysis showed an increase in the severity of atmospheric drought in the Lublin region, with intensification of this phenomenon in the last two decades, especially in the warmer half of the year (April, June–August). The main cause of drought in the Lublin region was identified as a statistically significant increase in air temperature (on average, from 0.4 °C to 0.7 °C/10 years in April, July and August, and from 0.2 °C to 0.5 °C/10 years in June) together with the absence of changes in precipitation in the warmer half of the year. This may be linked to some increase in the frequency of high-pressure circulation types, both non-directional and advection from the south. Due to the worsening problem of drought in Poland in recent years, especially in agriculture, there is a need for further research on this subject and for solutions aimed at optimizing agricultural use of the productive environment. [ABSTRACT FROM AUTHOR]

The aim of the study is to analyze the occurrence of hot days and heat waves in Poland, their intra-annual distribution, and their long-term variability, and to present the circulation factors favoring the appearance of extensive waves in the country. Hot days were days with Tmax not lower than the threshold value defined by the 95th percentile of summer Tmax in the period 1961–1990. Atmospheric circulation was described using sea level pressure, geopotential of 700 and 500 hPa level, and horizontal and vertical wind on these levels. A statistically significant increase in the number of hot days in the entire study period and a significant acceleration in growth after 1980 were shown. In the entire analyzed period, only 11 waves were found covering at least 25% of the country area and lasting no less than a week. Among them, only one occurred before 1990, and more than half were observed in the last decade. Four circulation patterns favoring the extensive heat waves were distinguished differing the location of main baric center location. Spatial and temporal distribution of vertical velocity anomalies allows distinguishing clear phases of strengthening, stabilization, and weakening of anticyclone accompanying the occurrence of a heat wave. [ABSTRACT FROM AUTHOR]

The primary purpose of the study was the determination of the spatial day-to-day variability of extreme air temperatures in Poland and the dependency of large temperature changes on atmospheric circulation in accordance with the Grosswetterlagen (GWL) classification. The goal was achieved based on data from 1966 to 2015, made available by the Institute of Meteorology and Water Management—National Research Institute. Day-to-day changes in maximum and minimum air temperatures were designated with a rate of ≥6 °C (large) and with a rate of ≥12 °C (very large) and their spatial distribution was presented. Finally, the analysis of the dependency of considerable temperature changes on atmospheric circulation in accordance with the Grosswetterlagen (GWL) classification was conducted. The obtained results showed that in Poland in the period 1966–2015 there was a statistically significant increase in the number of large changes in both Tmax and Tmin. The number of large changes in Tmax increases from north to south, and the number of large changes in Tmin from north to east and south of Poland indicate the range of the effect of marine and continental properties on the climate of Poland and the influence of local relief as well as the atmospheric circulation impact. Large changes in Tmax occur more frequently in spring and in Tmin in winter. Large changes in Tmax and Tmin are mainly recorded during cyclonic circulation, however, the anticyclonic circulation types favour especially large decreases in Tmin. [ABSTRACT FROM AUTHOR]