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Introduction and objective. The timings of Fraxinus and Betula flowering and pollen release overlap, which may cause increased allergic reactions in sensitive people. The aim of the present study was to characterize Fraxinus pollen seasons in Lublin (central-eastern Poland) and to identify meteorological factors that most determine the occurrence of airborne pollen of this taxon, as well as obtain forecast models for the basic characteristics of the pollen season. Materials and method. The study was conducted in Lublin during the period 2001–2016, employing the volumetric method. The seasons were compared by PCA (Principal Component Analysis). To determine relationships between meteorological conditions and the pattern of pollen seasons, regression analysis was used. Data for the period 2001–2015 were used to create forecast models by applying regression analysis, while the 2016 data served to verify these models. Results. Season end date and seasonal peak date were characterized by the lowest variation. The biggest differences were found for peak value and total annual pollen sum. The average dates of occurrence of ash pollen grains in the air of Lublin were between 13 April 13 – 3 May 3, whereas, on average, the pollen peak date occurred on 23 April. The factor loading values for the PC1 variable indicate that it is most strongly correlated with peak value and total pollen sum, while the PC2 variable correlated with the pollen season start date and season duration (a negative correlation). Regression models were developed for the following pollen season characteristics: season start, end and duration, seasonal peak date, and total annual pollen sum. Conclusions. The fit of the forecast models was at the level of 62–94%. Analysis of the data showed that weather conditions mainly in February were important factors controlling the Fraxinus pollen season. [ABSTRACT FROM AUTHOR]

The paper summarizes the mean daily air temperature in Lublin (data from the Meteorological Station UMCS) in two 30-year periods: 1951-1980 and 1981-2010. The range of variability and frequency of air temperature values was analyzed in 2- and 5-degree intervals. The mean air temperature in the years 1981-2010 was 8.7°C and it was higher than the mean air temperature for years 1951-1980 for 0.8°C. In the annual course during 10 months mean average monthly values were higher in the second period. The biggest differences concerned the months from January to March. The comparison of results obtained from two 30-year periods showed that the variability range of the mean daily air temperature has not changed (from -25.9 - -24.0°C to 28.1-30.0°C). however, the number of days with temperature > 20°C has significantly increased, on average by 6 days during the year, while the number of days with daily average temperature ≤ -10.0°C has decreased on average by 3 days in a year. In the annual course the highest changes in two analyzed periods are observed in January. In this month in the years 1981-2010 there was increase in the number of days with daily air temperature above 0.0°C by 4 days. [ABSTRACT FROM AUTHOR]