Multi-Annual Changes in Heat Stress Occurrence and Its Circulation Conditions in the Polish–Saxon Border Region

Abstract

Heat stress is one of the most critical factors affecting human life. In Central Europe, its influence is noticeable, especially in the Polish–Saxon region, which is a very popular tourist region also inhabited by a high number of elders. The main goal of this paper was to assess multi-annual changes in heat stress occurring in the region, considering the frequency of heat days, the UTCI (Universal Thermal Climate Index), and circulation conditions. The research showed that all the thermal and biothermal indices in this region significantly increased during 1971–2019 in the lowlands, the mountain foreland, and the lower mountain zone. In terms of the UTCI, a negative trend for cold stress frequency was noticed in the entire region in favor of an increase in a tendency toward thermoneutral conditions and heat stress. This concerns especially strong and very strong heat stress (UTCI > 32 °C), in which positive trends were observed for most of the stations located in the lower hypsometric zones. The results also showed that heat stress mainly occurs on days with anticyclonic circulation. Analysis of selected cases of heat waves in the 21st century indicated that the lower hypsometric zones are characterized by a very high UTCI, while the summit zone is free from heat stress occurrence.

Evaluation of Tourism-Climate Conditions in the Region of Kłodzko Land (Poland)

“…In the cold season, slight, moderate, and strong cold-stress categories were predominant. Similar conditions are typical for the regions located in the lowlands and the lower mountain zones of Poland and Central Europe [10,23,48,50,51,53,54,[66][67][68][69][89][90][91]. The analysis carried out in the paper showed that the frequency of moderate heat stress in July and August in the lower hypsometric zones of Kłodzko Land was about 5% lower than in the Carpathian region, confirming the results of the previous studies [48].…”

“…The research showed that one of the most important weather factors is heat stress, for which a rising tendency was observed for both indices-heat days and UTCI. The mean frequency of heat days in the lower hypsometric zones amounted to more than 3 days a year, which was comparable to the number observed in the lower mountain zone of the Western Sudety [68], the Silesian Foothills (southern Poland) [84], and in the coastal regions of Germany and Poland [22,24,88]. The multiannual changes indicated that heat-stress frequency has significantly risen over the last decades and can intensify in the following years.…”

“…In Słoszów, where the intensity of changes was the lowest, the rate was similar to the northern parts of Poland [88]. On the other hand, the increase for the stations located in Kłodzko Land was noticeably lower if compared to the lowland part of the Lower Silesia, where the frequency of heat days in 1971-2019 rose at the rate of more than 2 days per decade [68].…”

“…Simultaneously, the studies also indicated that the UTCI can be higher than 40 • C during the most intensive heat wave periods. Such conditions are also observed in the region of southwest Poland, including the lowlands [66] and the lower mountain zones of the Sudetes Mountains [48,[66][67][68]. The entire Sudetes region in the warm half-year is characterized by a relatively low number of days with thermoneutral conditions which are the most favourable for tourists and bathers [48].…”

“…The entire Sudetes region in the warm half-year is characterized by a relatively low number of days with thermoneutral conditions which are the most favourable for tourists and bathers [48]. On the other hand, in the higher parts of the Sudetes Mountains, the UTCI is more often related to cold stress, while heat stress is rarely observed, or does not occur at all [48,[67][68][69]. On the summits, cold stress prevails throughout the year, and the weather related to the most intensive cold stress can occur on more than 50% of winter days [69].…”