The objective of the present work is to present the temporal and spatial characteristics of the bioclimatic conditions of the Lubuskie Voivodeship. The daily timed values (12UTC) of meteorological elements in the period 1971-2006 from three stations (Słubice, Gorzów Wielkopolski and Zielona Góra) were used as the basis for the calculations. In order to assess the bioclimatic conditions, a thermal stress index UTCI (Universal Thermal Climate Index) that is calculated with the use of BioKlima 2.6 software was applied. The analysis shows that thermal stress related to 'slight and moderate cold stress' and 'no thermal stress' is a dominant factor (80%) affecting the bioclimatic conditions of the Lubuskie Voivodeship. During the analysed period, days with thermal stress related to cold stress occurred more frequently than those with thermal stress related to heat stress. On the basis of a linear regression trend, a positive trend for thermoneutral conditions days and heat related stress days (UTCI>32°C), as well as a negative trend for cold related stress (UTCI<-13°), were ascertained. Key words UTCI • bioclimatic conditions • stress category • Lubuskie Voivodeship • linear trend 38Agnieszka Mąkosza conditions, weather conditions and land use greatly affect the given area's bioclimate and its particular characteristics (Kozłowska-Szczęsna et al. 1997). As far as tourism and recreation are concerned, weather and climatic conditions are important nature values. The influence of the weather and climate on man is a complex issue, since it includes numerous physical conditions which change over time and space, and the physiological reactions of the human body when exposed to the stimuli of the atmospheric environment (Krawczyk 1995). Most case studies concerning bioclimatic conditions make use of compound indices that are based on human heat balance as regards the subjective thermal perception of a given organism. Recently, a new index -UTCI (Universal Thermal Climate Index) -has been developed (Błażejczyk et. al. 2010a(Błażejczyk et. al. , 2010b. It is based on a multi-node model of the human heat balance which considers heat transfer occurring in the human body and on its surface, and physiological thermoregulatory mechanisms. Data obtained with the use of UTCI constitute objective thermal stress values. It is valid to analyse bioclimatic conditions in this region of Poland since case studies concerning climatic conditions of this region, especially bioclimatic conditions, are relatively rare (Kalbarczyk & Kalbarczyk 2008; Mąkosza 2009; Mąkosza & Michalska 2010, 2011. The results can be of use to local and administrative authorities of the voivodeship and provide insight and data which can be useful for promotion and tourism. The objective of this work is to present the temporal and spatial variability of UTCI and assess the bioclimatic conditions of the lakeland type area as confined to the administrative borders of the Lubuskie Voivodeship. Materials and methodsMeteorological data was obtained from three w...

The ongoing climate warming affects, among others, and the variability of thermal conditions in spring and autumn are resulting in earlier dates of the beginning and end of the growing season. The present paper provides detailed characteristics of the phenomenon of ground frosts, addressing the question of whether the risk of frost-related damage in the extending growing season is still present. The assessment of temporal and spatial distribution of ground frosts (5 cm above ground level-AGL) in Poland in the thermal growing season (AT > 5 °C) was conducted on the basis of the results of air temperature measurements at 5 and 200 cm a.g.l. obtained from 52 station of the Institute of Meteorology and Water Management—National Research Institute for the period 1971–2020. The thermal growing season was calculated using the method by Gumiński. The following were calculated: the dates of the occurrence of ground frosts in spring and autumn, duration of the frost-free period, the number of days with frosts of various intensity, according to years, ten-day period and days in a year together with trends of change. The conducted analysis demonstrated that the number of days with frosts in the thermal growing season in the multiannual period under analysis (1971–2020) does not show any statistically significant changes. It was found that in the thermal growing season, the average number of days with ground frosts in Poland amounts to 28 and ranges in spring from 15 to 22, and in autumn from 8 to 12. Most frequently, approx. 49%, slight frosts are recorded, followed by moderate (29%), severe (15%) and very severe (7%). A positive effect of water reservoirs on decreasing the frequency and intensity of frosts, as well as sporadic occurrence of the phenomenon in the second half of June were demonstrated. Statistically significant earlier dates of disappearance of frosts in spring, later dates of occurrence in autumn and the lengthening of the frost-free period from approximately 2 days in the north-east of Poland to approximately 8.0 days over 10 years in the Pomerania region, create increasingly more favourable conditions for the cultivation of plants with high thermal requirements in Poland.

Frosts cause damage to plants in field crops and also trees, thus contributing to heavy economic losses in agriculture. One of the consequences of climate warming is the lengthening of the thermal growing season (AT > 5 °C) and acceleration of phenological phases as well as the lengthening of the frost-free period. This favourable element allows the extension of the range of cultivated plants to include plants requiring warmth and a longer development period. The present study concerns the area of Poland. The data on mean and minimum 24-h period air temperature (200 cm above ground level—AGL) were obtained from 52 meteorological stations of the Institute of Meteorology and Water Management—National Research Institute (IMGW-PIB) for the period 1971–2020. A day with air frost was identified when the recorded minimum air temperature was below 0.0 °C and the mean 24-h period air temperature was above 0.0 °C. All calculations concerning frosts were limited to the period with mean 24-h period air temperature >5 °C (the growing season) as determined with the Gumiński method. The obtained results show that in the thermal growing season (AT > 5 °C) in Poland, no statistically significant change in the average number of days with air frosts in the period 1971–2020 was found. On average, in Poland, in the years 1971–2020, a lengthening of the thermal growing season by 6.2 days over 10 years was identified. Earlier disappearance of the latest air frosts in spring was identified as 2 to 3 days over 10 years, and the later occurrence of air frosts in autumn as 1 to 4 days over 10 years. The share of severe (−4.1°C ÷ −6.0 °C) and very severe (<−6.0 °C) frosts in the total number of days with air frosts in Poland amounts to, on average, 5.8% in spring and 2.6% in autumn.

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