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Significant changes in climate variables in the last decades resulted in changes of perceived climate conditions. However, there are only few studies discussing long-lasting changes in bioclimatic conditions. Thus, the purpose of this paper is to present the temporal and spatial distribution of hazardous heat and cold stress conditions in different regions of Poland. Its focus is on long-lasting changes in such conditions in the period 1951–2018. To assess changes in hazardous thermal stress conditions, the Universal Thermal Climate Index (UTCI) was used. UTCI values at 12 UTC hour (respectively 1 pm winter time, 2 pm summer time) were calculated daily based on air temperature, relative humidity, total cloud cover and wind speed at 24 stations representing the whole area of Poland. We found that the greatest changes were observed in minimum (1.33 °C/10 years) and average (0.52 °C/10 years) UTCI values as well as in cold stress frequency (− 4.00 days per 10 years). The changes vary seasonally and regionally. The greatest increase in UTCImin and decrease in cold stress days were noted from November to March and had the highest values in north-east and east Poland, and also in the foothills of the Carpathian Mountains. The trends in maximum UTCI are much smaller and not always positive. The spatially averaged trend in UTCImax for Poland as a whole was 0.35 °C/10 years and the increase in heat stress days was 0.80 days/10 years. The highest increases in UTCImax and heat stress days were noted in eastern and south-eastern Poland. Supplementary Information The online version contains supplementary material available at 10.1007/s00484-020-02069-7.

The assessment of thermal stress stimuli in Poland was based on the Universal Thermal Climate Index (UTCI). Daily values of UTCI at 24 stations selected to represent the whole area of Poland at 12:00 UTC were calculated over the period 1951-2018. Various UTCI characteristics, i.e., spatial averages of daily, monthly and annual values, daily spatial contrasts (i.e., the difference between daily highest and lowest UTCI values) were defined in each of 8 bioclimatic regions of Poland. Ten-year trends for UTCI and spatial contrast values were counted and their statistical significance was analysed. A statistically significant increase in UTCI values was found in all the regions of Poland. However, contrasts in thermal stress both for Poland as a whole and in most of the regions decreased significantly, especially in the north-east of Poland, the country’s coldest region. This indicates a reduction in the stimuli of thermal environment in Poland and in most of the individual regions.

Mountain areas create specific features of local climates (by modification of air circulation, insolation, air temperature, precipitation, wind regime) and greatly affect ambient weather conditions which influence different kinds of human (climbing, skiing, walking, etc.). However, till now only few studies of human bioclimate in individual mountain ridges in Europe were done. The aim of the present study is to assess thermal stress features represented by Universal Thermal Climate Index (UTCI) in nine mountain systems in Central and Eastern Europe. 37 meteorological stations located at altitudes of 237-3580 m above sea level were considered. The data represent midday observational term and cover the period 2000-2017. Mean, highest and lowest annual thermal stress values and annual frequency of cold and heat stress days are analysed The conducted studies have demonstrated that in the examined mountain systems thermal stress conditions are dependent (though to a various extent) mostly on altitude (UTCI values and heat stress days decrease and number of cold stress days rise significantly due to increase of altitude). However, impacts of latitude and longitude is well seen only in altitude belt of 300-1000 m a.s.l.

While significant increases in air temperature are being observed in the context of climate change, precipitation characteristics, indicators and indices seem to be changing in a more regionally-variable manner. High-mountain areas prove particularly subject to fluctuations and changes of climate, given that mountains serve as barriers to masses of air flowing over them, with the result that atmospheric precipitation totals are high in the context of the so-called orographic rainfall. Overall, the Chornohora represents the highest range anywhere in Ukraine’s Carpathian Mts, as there are six peaks over 2000 m a.s.l. capable of serving as a barrier running NW-SE. Nevertheless, the main ridge of the High Tatras (of the Slovakia-Poland borderland) is even higher and runs W-E. Each massif is some 30 km in length, while the two ranges are separated by a distance of almost 350 km. Main drainage divides run along the highest ridges here, with the Tatras separating the drainage basins of the Vistula and Danube, while the Chornohora represent a divide between the Prut and Tysa basins. The aim here has been to present characteristics of atmospheric precipitation in Tatra and Chornohora Mts. as these are seen to relate to atmospheric circulation. To this end, the dependent relationship between intensity of precipitation and atmospheric circulation was examined exhaustively, with changes in the latter considered from the point of view of intensity of precipitation in the massifs under study, and with trends for precipitation over the study period also looked for.The Niedźwiedź (2017) classification of types of atmospheric circulation was applied, with annual values calculated for circulation indicators P (a W-E inflow), S (a S-N inflow) and C (a cyclonic/anticyclonic inflow). Overall, the study drew on 1961‑2015 daily precipitation data from the north-eastern slope of Chornohora Mts. (as represented by Ukraine’s Pozhyzhevska weather station, PO, 1451 m a.s.l.), as well as the north slope of the Tatra Mts. (as represented by Poland’s Hala Gasienicowa weather station, HG, 1520 m a.s.l.).An air inflow from western directions was found to have prevailed over 28% of the days in the average year (Fig. 1). The most frequent types involved here were: Ka (12%), Bc (10%), Wc (10%) and Wa (8%). During the summer months (JJA), it is the Ka and Bc types that are even more frequent (present on approx. 15% of summer days). Types Wc and Wa in turn occur more frequently in winter (DJF) – respectively 13% and 12% of the time. In autumn, these types reach a level of occurrence around 10%.At 1712 mm, the average annual rainfall total for Tatra Mts is higher than that for the Chornohora (on 1446 mm). While the seasonal distribution of rainfall in spring and autumn looks almost the same in the two massifs, winter brings more precipitation in the Chornohora, while summer is a wetter season in the Tatras (Fig. 2). Largest amounts of precipitation nevertheless fall in the warm half-year, in the circumstances of N+NEa advection, cyclonic situations and under arctic, polar-marine or polar-marine transformed air masses (Figs. 3 and 4).The largest changes over time are to be observed for the zonal inflow index (P) and the cyclonic index (C). The P index points to increased numbers of days with a western circulation, while the C index confirms the domination of anticyclonic circulation (Fig. 5). The trend for annual rainfall totals is an upward one overall in both regions, but in neither does this achieve statistical significance (Fig. 6). Equally, there is a downward trend line for numbers of days featuring precipitation (RRdays) in the cases of both the Chornohora and Tatra ranges (equal to -7.3 days/10 years and -7.59 days/10 years respectively) (Fig. 7). On the other hand, the trend for numbers of days with higher rainfall, e.g. with RRdays>10mm is upward for the Chornohora (at +1.23 days/10 years), but downward for the Tatra Mts (at -0.6 days/10 years) (Fig. 8).

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. Supplementary Information The online version contains supplementary material available at 10.1007/s00484-021-02202-0.

Background: Mountaineers must control and regulate their thermal comfort and heat balance to survive the rigors of high altitude environment. High altitudes feature low air pressure and temperatures, strong winds and intense solar radiation, key factors affecting an expedition’s success. All these climatic elements stress human heat balance and survival. We assess components of human heat balance while climbing Mt. Everest.Materials and Methods: We calculated climbers’ heat balance using the Man-ENvironment heat EXchange model (MENEX-2005) and derived meteorological data from the National Geographic Expedition’s in situ dataset. Three weather stations sited between 3810 and 7945 m a.s.l. provided data with hourly resolution. We used data for summer (1 May–15 August 2019) and winter (16 October 2019–6 January 2020) seasons to analyze heat balance elements of convection, evaporation, respiration and radiation (solar and thermal).Results: Meteorological and other factors affecting physiology—such as clothing insulation of 3.5–5.5 clo and activity levels of 3–5 MET—regulate human heat balance. Elevation above sea level is the main element affecting heat balance. In summer two to three times more solar radiation can be absorbed at the summit of the mountain than at the foot. Low air pressure reduces air density, which reduces convective heat loss at high altitude by up to half of the loss at lower locations with the same wind speed and air temperature.Conclusion: 1. Alpinists face little risk of overheating or overcooling while actively climbing Mt. Everest, despite the potential risk of overcooling at extreme altitudes on Mt. Everest in winter. 2. Convection and evaporation are responsible for most of the heat lost at altitude. 3. Levels of physical activity and clothing insulation play the greatest role in counteracting heat loss at high altitude.

Artificial light has been present in human life for decades but our knowledge of its effects is still insufficient. Lighting lets us be active longer, gives us a sense of security and provides aesthetic experiences. Despite all of these advantages, in urban areas artificial light also has a negative effects on the environment and human life. Although light pollution is one of the most common forms of anthropogenic environmental change, this phenomenon remains insufficiently investigated. The present work thus focuses on night sky brightness and artificial factors impacting the level of the phenomenon using Warsaw (Poland) and Fukuoka (Japan) as an example. The basis of the study is the new World Atlas of Artificial Night Sky Brightness. Moreover, we used image data from the Visible Infrared Imaging Radiometer Suite Day/Night Band and data from field research to analyse the primary artificial light characteristics in the two cities: illumination, colour temperature, peak wavelength, dominant wavelength, stimulation of photoreceptors, design of lighting fixtures and radiance. The results indicate that Warsaw (area: 517.2 km2; population: 1 777 972) is characterized by higher light pollution than Fukuoka (area: 343.5 km2; population: 1 554 229). Skyglow is primarily influenced by the number of light sources; however, local differentiation of the phenomenon depends on the spectral characteristics and design of lighting fixtures. Moreover, environmental features may affect light pollution through scattering, reflection and absorption. Outdoor lighting in Warsaw was characterized by a higher value of light illumination and greater stimulation of photoreceptors sensitive to long and medium waves. However, the lighting infrastructure in Fukuoka was also unsuitable, as it was characterised by high values of colour temperature and stimulation of photoreceptors sensitive to short waves and ganglion cells, which may be detrimental to the human body.

This paper assesses changes in bioclimatic conditions in Poland using two indices: the Universal Thermal Climate Index (UTCI) and Physiological Subjective Temperature (PST). The indices were calculated using the BioKlima 2.6 software package on the basis of several meteorological parameters (temperature, humidity, cloudiness, wind speed), measured daily at 12:00 UTC, from the period 1951–2018 at 24 stations representing different biometeorological regions. First, the spatial distribution of UTCI and PST values and the frequency of different thermal stress and thermal sensation categories are presented, with the various thermal stress and sensation categories grouped into 3 for each index. Then, the absolute values and relative percentage trends (compared to 1951) are calculated for ten-year periods and days with specific characteristics. The analysis shows a significant increase in the minimum and mean values of the applied indices during the period under investigation over all areas of Poland, including the mountains, especially in the north-east (where UTCI minimum values rose up to 1.8 °C per decade) and Tarnow in the south-east (up to 2.2 °C per decade). The rise of UTCI summer maximum values was significant only in the north-east and north-west of Poland (0.3–0.5 °C per decade) and in the mountain foothills (0.3–0.4 °C per decade). The changes in PST maximum values were insignificant. On average, in every decade, the number of cold days reduced by 2.7 in the case of PST and 3.2 on the UTCI. However, in the north-east, the reduction was much greater, at 7 days per 10 years (UTCI) and 6 days when considering PST. Regionally, the greatest increase in the mean and minimum values of the indices used and the decrease in the frequency of cold days were observed in north-eastern, eastern and western Poland, i.e. the regions most exposed to frequent changes in air circulation, which is hypothesised to play the main role in shaping bioclimatic conditions in Poland.

Mountain areas are ecosystems very vulnerable to fluctuations and changes of climate. As a consequence, research into climate and climate change in Poland’s Karkonosze and Tatra Mountains has been ongoing for several years now, and has already yielded essential information regarding these highest ranges in Poland. However, there remains a paucity of research comparing features of climate in the two chains of mountains. In consequence, the work detailed here has sought to compare key climate characteristics in these ranges, as well as their seasonal and multiannual changes over the period 1951‒2015. The research is based on daily meteorological records from within the network of Poland’s Institute of Meteorology and Water Management – National Research Institute. In the case of the Karkonosze Mts., it was the meteorological stations at Śniezka (Ś, 1603 m a.s.l.) and Jelenia Gora (JG, 344 m a.s.l.) that were chosen; while in the Tatras the selected stations were on Kasprowy Wierch (KW, 1990 m a.s.l.) and in Zakopane (Z, 857 m a.s.l.). Additionally, the station at Hala Gąsienicowa (HG, 1520 m a.s.l.) was considered in line with data available for the shorter 1981‒2015 period. The research took account of daily data on air temperature, relative humidity of the air, wind speed, precipitation and snow cover. Specifically, the climate characteristics calculated and analysed by reference to mean multiannual, yearly and seasonal values related to air temperature, maximum temperature, minimum temperature, precipitation totals and maximum snow depth. Further analysis related to numbers of days with precipitation and snow cover, as well as numbers of days with specific air temperatures described as hot (Tmax >25°C), frosty (Tmax

Mean annual and monthly averages of mean (Tmean), maximum (Tmax) and minimum (Tmin) air temperature from seven stations in Iraq were analysed to detect the inter-annual variation, long-term temporal and spatial trends distribution over the period 1941–2013. Due to non-homogeneous problems, this period has been divided into two short separated periods (1941–1980 and 1995–2013), in order to compute temperature trends. In this context two statistical tests were used: linear regression and Mann-Kendall. The time series of mean annual temperature indicate the current warming period over Iraq identical with the global warming, which has started since the middle of seventh decade of the last century. The 2010 was the warmest year in all stations. Three distinct inter-annual temperature variation patterns were observed. These were probably the effects of micro-scale and meso-scale factors. The first one represents central and northern Iraq. The second represents the south of Iraq and Kirkuk station and the third one is a characteristic for eastern Iraq. Temperature trend analysis revealed that there are general upward trends with the strongest warming trends identified in the summer months which are around 89 % of the total significant monthly trends. Spatially, in both periods the southern region of Iraq is most affected by the warming trend in Tmean and Tmax. When considering Tmin, the southern and northern regions both are affected by warming with more pronounced trend intensity in the northern stations. No significant trend occurs Hai station in both periods and Baghdad has the still less trend value. In the first period the highest rise of Tmean and Tmax values are observed in July and June in Nasiriya station at 0.61 °C/decade and 0.63 °C/decade, respectively and in Mosul station for Tmin in August is 1.41 °C/decade. Moreover, in the period from 1995 to 2013, the highest warming trend of Tmean and Tmax were in Hai station for March at 1.48 °C/decade and at 1.85 °C/decade, respectively. Baghdad station experienced the highest significant trend for Tmin in August at 1.89 °C/decade.

The climate and bioclimate of the city have been studied by the climatologists from IGSO PAS since the 1960s. Since the late 1990s, these studies have been based on the measurement network of thermal and humidity conditions in the Warsaw agglomeration. The number of measuring posts has been changed over the years, currently it consists of 27 posts. The main research issues are: temporal and spatial changes of urban heat island under the spatial development changes, methods of limiting the urban heat island and adaptation to it, the impact of biologically vital areas on local climate, forecasts for the urban heat island based on selected climate change models and scenarios of spatial development changes. A large number of studies by the IGSO PAS climatologists concern human bioclimatology, including the thermal sensation, the impact of heat waves and cold waves on morbidity and mortality, the role of greenery in the city (cooling, but also aggravating allergy). The main goal of this research is to determine the measures limiting the negative impact of the urban climate on people and to improve the quality of life in the city.

The growing need for valid assessment procedures of the outdoor thermal environment in the fields of public weather services, public health systems, urban planning, tourism & recreation and climate impact research raised the idea to develop the Universal Thermal Climate Index UTCI based on the most recent scientific progress both in thermo-physiology and in heat exchange theory. Following extensive validation of accessible models of human thermoregulation, the advanced multi-node 'Fiala' model was selected to form the basis of UTCI. This model was coupled with an adaptive clothing model which considers clothing habits by the general urban population and behavioral changes in clothing insulation related to actual environmental temperature. UTCI was developed conceptually as an equivalent temperature. Thus, for any combination of air temperature, wind, radiation, and humidity, UTCI is defined as the air temperature in the reference condition which would elicit the same dynamic response of the physiological model. This review analyses the sensitivity of UTCI to humidity and radiation in the heat and to wind in the cold and compares the results with observational studies and internationally standardized assessment procedures. The capabilities, restrictions and potential future extensions of UTCI are discussed.

The important requirement that COST Action 730 demanded of the physiological model to be used for the Universal Thermal Climate Index (UTCI) was its capability of accurate simulation of human thermophysiological responses across a wide range of relevant environmental conditions, such as conditions corresponding to the selection of all habitable climates and their seasonal changes, and transient conditions representing the temporal variation of outdoor conditions. In the first part of this study, available heat budget/two-node models and multi-node thermophysiological models were evaluated by direct comparison over a wide spectrum of climatic conditions. The UTCI-Fiala model predicted most reliably the average human thermal response, as shown by least deviations from physiologically plausible responses when compared to other models. In the second part of the study, this model was subjected to extensive validation using the results of human subject experiments for a range of relevant (steady-state and transient) environmental conditions. The UTCI-Fiala multi-node model proved its ability to predict adequately the human physiological response for a variety of moderate and extreme conditions represented in the COST 730 database. The mean skin and core temperatures were predicted with average root-mean-square deviations of 1.35 ± 1.00°C and 0.32 ± 0.20°C, respectively.

The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity (but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research and application in human biometeorology.

Over the past century more than 100 indices have been developed and used to assess bioclimatic conditions for human beings. The majority of these indices are used sporadically or for specific purposes. Some are based on generalized results of measurements (wind chill, cooling power, wet bulb temperature) and some on the empirically observed reactions of the human body to thermal stress (physiological strain, effective temperature). Those indices that are based on human heat balance considerations are referred to as "rational indices". Several simple human heat balance models are known and are used in research and practice. This paper presents a comparative analysis of the newly developed Universal Thermal Climate Index (UTCI), and some of the more prevalent thermal indices. The analysis is based on three groups of data: global data-set, synoptic datasets from Europe, and local scale data from special measurement campaigns of COST Action 730. We found the present indices to express bioclimatic conditions reasonably only under specific meteorological situations, while the UTCI represents specific climates, weather, and locations much better. Furthermore, similar to the human body, the UTCI is very sensitive to changes in ambient stimuli: temperature, solar radiation, wind and humidity. UTCI depicts temporal variability of thermal conditions better than other indices. The UTCI scale is able to express even slight differences in the intensity of meteorological stimuli.

The Universal Thermal Climate Index (UTCI) was conceived as a thermal index covering the whole climate range from heat to cold. This would be impossible without considering clothing as the interface between the person (here, the physiological model of thermoregulation) and the environment. It was decided to develop a clothing model for this application in which the following three factors were considered: (1) typical dressing behaviour in different temperatures, as observed in the field, resulting in a model of the distribution of clothing over the different body segments in relation to the ambient temperature, (2) the changes in clothing insulation and vapour resistance caused by wind and body movement, and (3) the change in wind speed in relation to the height above ground. The outcome was a clothing model that defines in detail the effective clothing insulation and vapour resistance for each of the thermo-physiological model’s body segments over a wide range of climatic conditions. This paper details this model’s conception and documents its definitions.

The problem of the heat balance of the human body under unstationary thermal conditions was examined. A heat balance model was used. Some days with different weather conditions were taken for comparative analysis of the heat balance and thermal stress hazard. During all warm and hot days, thermal stress was observed. Problems of thermal sensations and state of pleasantness were discussed also.

Different methods have been compared for the estimation of solar heat load on man. The comparison comprised several methods based on the calculation of absorbed solar radiation and one method for calculation of mean radiant temperature (Mrt). Regression analysis was carried out for predicted values and values calculated for a vertical cylinder, assumed as an analog model of a standing man. Regression of mean skin temperature, measured in 10 subjects exposed to solar radiation under a variety of climatic conditions, on predicted radiant heat load was also analysed. Mean skin temperature correlated best with Mrt, accounting for more than 50% of the variance. The results indicated that three methods provide a realistic estimation of the radiation heat load, whereas some methods show deviations of several hundred per cent.

During the last century about 100 indices were developed to assess influences of the atmosphere on human being. However, most of them have not close relationships with physiological reactions in man. In 1999 International Society of Biometeorology established special study group do develop new Universal Thermal Climate Index (UTCI). Since 2005 these efforts have been reinforced by the COST Action 730 (Cooperation in Science and Technical Development). In February 2009 the Action was terminated and UTCI was developed. The new UTCI index represents air temperature of the reference condition with the same physiological response as the actual condition. The index base on Fiala model that is one of the most advanced multi-node thermophysiological models and include the capability to predict both whole body thermal effects (hypothermia and hyperthermia; heat and cold discomfort), and local effects (facial, hands and feet cooling and frostbite). The model consists of two interacting systems: the controlling active system; and the controlled passive system. The assessment scale of UTCI bases on the intensity of objective physiological reactions to environmental heat stress in wide range of weather and climates. The index can be applicable in various research, for example in weather forecasts, bioclimatological assessments, bioclimatic mapping in all scales (from micro to macro), urban design, engineering of outdoor spaces, consultancy for where to live, outdoor recreation and climatotherapy, epidemiology and climate impact research. The paper presents thermophysiological principles of UTCI as well as some examples of its application to assess bioclimatic differentiation of Europe.