Heat waves in Poland in the period 1951-2015: trends, patterns and driving factors (original) (raw)
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Heatwaves in Poland–Frequency, Trends and Relationships with Atmospheric Circulation
2009
The daily minimum and maximum temperatures at seven Polish stations were used in an analysis of the occurrence of heatwaves in the years 1951-2006. Heatwaves were defi ned as days with temperatures exceeding selected thresholds (t max ≥25°C, t max ≥30°C, t min ≥18°C). The mean length of a wave of very warm days lasts from 2-4 days, the longest no fewer than 23 days. Waves comprising hot days and nights are shorter. The frequencies of very warm and hot days and hot nights increased in the analyzed period, especially its second half (1979-2006). The occurrence of heatwaves characteristically links up with high-pressure systems over Central Europe, along with associated blocking episodes.
Atmosphere
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 distinguish...
Strong heat and cold waves in Poland in relation with the large-scale atmospheric circulation
Theoretical and Applied Climatology
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 northeastern 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.
Trends of minimum and maximum temperature in Poland
2002
The variability of minimum and maximum temperature and the daily temperature range (DTR) in Poland was analyzed on the basis of the data from 9 stations with different periods of data (the longest was 98 yr). The long-term changes of seasonal means as well as for all Julian days were determined. The increase in the minimum temperature was accompanied by a slighter increase in the maximum temperature and a decrease in the DTR. It was found that the DTR changes correlate well with cloudiness, and the extreme temperature changes are related to the NAO (North Atlantic Oscillation) intensity, especially during winter and spring. The analysis of intra-annual changes has shown that the strongest increase in the minimum and maximum temperatures occurs in mid-and late winter, but there are also periods with decreasing tendencies, i.e. late autumn, the beginning of winter and the beginning of summer. All temperature indices indicate the cooling in autumn. KEY WORDS: Daily minimum and maximum temperature • Daily temperature range • Long-term trends • Poland Resale or republication not permitted without written consent of the publisher
Has the frequency or intensity of hot weather events changed in Poland since 1950?
2012
Various indices of hot weather frequency and intensity were analysed in the area of Poland in the period between 1951 and 2006. An increase of majority of them was shown in the whole year and all summer months but September, when significant decrease in all indices was apparent. The correlation of selected hot weather indices and precipitation totals in a month of hot weather event and the preceding months were also calculated to check if prolonged dry weather can constitute a forcing factor for hot event creation. Because significant correlations appear mainly in the cases when precipitation is for the same month as the hot weather index, it seems that in Poland the presence of high pressure systems is a more important factor of hot event creation than dry weather.
The extreme year—analysis of thermal conditions in Poland in 2018
Theoretical and Applied Climatology
The study objective was the determination of thermal conditions in Poland in 2018 on the background of the multi-annual period 1966-2018. The study was based on data obtained from the Institute of Meteorology and Water Management-National Research Institute. The research showed a statistically significant increase in mean daily air temperature in the years 1966-2018. The highest mean annual air temperature over the prevailing area in the analysed multi-annual period was recorded in 2018. In that year, mean air temperature was lower than the mean value from the multi-annual period only during 2 months (February and March). The highest anomalies of mean monthly air temperature were observed in April.
The occurrence of hot weather in the Lublin-Felin and Czesławice in relation to atmospheric circulation (1966-2010), 2016
The paper describes the occurrence of hot (tmax 25.1–30.0°C) and very hot days (t max >30°C) in Lublin-Felin and Czesławice in the years 1966–2010. The analysis covers the long-term variability of such days, and duration of heat waves. Their circulation conditions were also determined, with indication of circulation types during which the probability of occurrence of hot and very hot days was the highest. In the study area, hot days occurred from April to September, and very hot days from May to August, with the highest frequency in July in both cases. In the period from 1991 to 2010, a considerably higher number of cases of very hot days were recorded than in the 1970s and 1980s. Moreover, they occurred in increasingly long sequences, contributing to more frequent occurrence of unfavourable thermal and humid conditions during the growing season of plants. The highest probability of occurrence of hot and very hot days was determined for circulation types with airflow from the southern sector, and the lowest from the northern sector. Should the upward trend in the frequency of very hot days continue, the risk of the effect of such unfavourable thermal conditions on the health and well-being of tourists and patients of the health resort in Nałęczów will also increase.
The heat goes on—changes in indices of hot extremes in Poland
Theoretical and Applied Climatology, 2016
On the basis of temperature observations at 60 meteorological stations in Poland, changes in the indices associated with the presence of extremely high air temperatures were examined. Indices associated with heat waves, such as the number of hot days (T max ≥30°C) in the summer months (June, July, August) and beyond the summer months (May, September), the number of extremely hot days (T max ≥35°C), the duration of the longest hot spell in the year, as well as the number of tropical nights (T min ≤20°C) were calculated. Spatial distribution of change rate in days per decade for the studied indices as well as the significance level of the observed trends is illustrated. Also current values of the studied indices (for 1991-2013) are examined and compared with the reference period, 1961-1990. For eight of 11 analysed indexes, increase has been detected in last decades with the help of the Mann-Kendall test at a significance level ≥0.05 or better, for a large group of stations. Statistically significant increases of the number of hot days in summer, the number of tropical nights in a year, and duration of the longest hot spell in summer were found for more than half of the stations. Distinct changes in the duration of heat waves were also noted. In 1961-1990, the longest hot spell lasted for 10 days while in 1991-2013, there were many hot spells longer than that, while the longest hot spell recorded in this period lasted for 17 days. Beyond summer, changes in the number of hot days were smaller. In May, a statistically significant increase was recorded for only three stations, while in September the downward trend was dominating and for eight stations it was statistically significant.
Contemporary changes of thermal conditions in Poland, 1951-2015
Bulletin of Geography. Physical Geography Series, 2016
The main subject of the research whose outcomes are presented in this paper is the spatial and temporal variability of thermal conditions in Poland during the period from 1951 to 2015. The analysis revealed the occurrence of symptoms indicating a systematic and sustained warming. Significant growth is observed in mean and extreme temperatures and their extreme percentiles, as well as in annual number of hot days, warm waves and their duration. In turn, downward trends are noted in series of the annual number of frost days, as well as in the number of cold waves and their duration. The results obtained confirm the thermal pattern determined for the whole region, especially for the southern part of the Baltic Sea basin.
Features of Multiannual Air Temperature Variability in Poland (1951–2021)
Atmosphere
Over the last 71 years, the air temperature in Poland has increased on average by 0.28 °C per decade—which gives a total change in this period exceeding 2 °C. The subject of this study was an analysis of the long-term variability of the Polish climate in terms of thermal characteristics. The aim of the research was to verify the hypothesis on the lack of homogeneity of this change and to identify points of significant acceleration of the observed tendencies. The analysis utilized the average monthly air temperature at selected synoptic stations in Poland over the period 1951–2021. The values were then processed into a reference series using Alexandersson’s method, which provided synthetic information on the variability in thermal conditions in the country. The analyses were carried out on an annual and seasonal basis. The values of the trend coefficients (and their statistical significance) were also calculated in shorter periods (minimum 30 years), which enabled determination of th...