Charakterystyka sezonu pyłkowego brzozy (Betula L.) w Krakowie na tle warunków meteorologicznych

The parameters of the birch pollen seasons in Cracow in 1991-2008 were analysed in relation to some meteorological elements and synoptic situations (circulation types, air masses and atmospheric fronts). Two types of the pollen seasons were distinguished - highly dense and less dense. The first type of the season started on the $15^{th}$ of April (on average), lasted 11-20 days and the maximum daily concentration exceeded 500 pgm-3. The less dense type started generally earlier (the first decade of April), lasted more than 20 days and the peak days were unstable. In this type of the pollen season, two peak days were often observed. The relationship between the type of the season and the meteorological conditions before the season was pointed out. Additionally, the influence of circulation types, types of air masses and atmospheric fronts over south-eastern Poland on a given day on the number of days with a daily concentration > 80 $pgm^{-3}$ was analysed. The relationship between the pollen season type and meteorological conditions before the season was found, among others, the influence of types of synoptic situations and air masses on the number of days with a concentration of over 80 $pgm^{-3}$ was established