This paper provides a meteorological overview of the 2015 mega‐heatwave (MHW) over Poland and compares the event with other MHWs in the region since World War II (up until 2015). A mega‐heatwave is defined as an event with at least 6 consecutive days with a maximum air temperature in excess of 30°C. These events are analysed here using observational meteorological data from ten major cities in Poland and neighbouring countries, along with 0.25° × 0.25° analysis fields from the Global Forecast System (GFS). Although the various events had different regional characteristics, in general they were caused by the inflow of a hot tropical air mass from the south, and were perpetuated by a high‐pressure system to the east of Poland and in some cases a low‐pressure system to the west. The 2015 MHW was the most extreme of the studied events, lasting from 9 days in Bialystok to 14 days in Warsaw and Poznan.

No abstract

The paper analyses the temporal and spatial variability of the Universal Thermal Climate Index (UTCI) in Poland in summer. Summer is the season with the highest intensity of tourism traffic that is why it is important to determine biometeorological conditions, especially in popular tourist destinations such as coastal, mountain and urban areas, in the times of climate changes. The analysis was based on data from 18 stations of IMGW-PIB (Institute of Meteorology and Water Management-National Research Institute), distributed evenly in the territory of the country, and representing all eight bioclimatic regions. The data include air temperature, relative humidity, wind velocity and cloudiness at 12 UTC from summer months: June, July and August from the years 2001-2018. Thermoneutral zone was the most frequently occurring UTCI class in Poland. It was recorded during 56-75% of summer days (with the exception of mountain stations, where it occurred on 30-35% of days). Moderate heat stress is the second most frequently occurring category with a frequency from 18 to 29% with the exception of mountain and coastal areas. Extreme and very strong cold stress occurred particularly in high mountain stations, and was sporadically observed at the coast of the Baltic Sea; however, the occurrence of such conditions decreases, which if favourable for beach tourism. No cases of extreme heat stress were recorded in any of the stations. The most unfavourable bioclimatic conditions were characteristic of the Upland Region (IV), represented by Kraków and Sandomierz, where very strong heat stress occurred with a 10% frequency. This is a limitation for urban tourism in those regions. The highest UTCI values were recorded in Kraków on 17 July 2007 and 29 July 2005. The highest number of cases with strong and very strong heat stress was recorded in 2015 as a consequence of the heat wave observed in Poland in the first half of August. In the majority of the analysed stations, in the second half of the analysed period (2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018), an increase in the number of days with strong and very strong heat stress was observed in comparison with the first half of period (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009). The highest frequency of such days was observed in July. Based on the data, there are 4 potential periods of occurrence of such days, with two most intense being 26. July-13 August and 14-22 July.

Abstract. This study evaluates the relationship between atmospheric circulation conditions and the frequency of heat/cold stress in Lublin in the years 1951-2010 according to the Universal Thermal Climate Index (UTCI). The paper outlines the frequency and conditional probability of heat/cold stress during particular circulation types and analyses the circulation patterns that induce these incidences. Increased wind velocity had a significant effect on creating unfavourable bioclimatic conditions in winter. Meanwhile, in summer, heat stress was observed almost exclusively when a high pressure system from eastern Europe induced a slow inflow of very warm air masses from the east or south.

Characteristics of heatwaves in Lublin in the years 1951–2015, along with a description of the circulation conditions of heatwaves, are discussed in this paper. A heatwave is defined as the occurrence of at least 3 consecutive days with an air temperature Tx > 30 °C. It can be affected by circulation patterns, which are presented in the form of average distribution maps (i.e. sea level pressure and air temperature in the lower troposphere over the European continent). The occurrence of heatwaves in Lublin is determined by anticyclone stagnation to the east of Poland as well as the surface low‐pressure gradient patterns located over western and central Europe. In recent years, the recorded numbers of days with Tx > 30 °C and the persistence of hot weather have increased (compared to the period 1971–1990). Moreover, extreme values (i.e. when Tx > 35 °C) are observed more frequently in contrast with previous decades.