Air Pressure Change

The present study takes into account the average daily values of atmospheric pressure reduced to sea level (SLP) from 43 meteorological stations for the years 1966–2018. The exceptions are the three mountain stations (Zakopane, Śniezka and Kasprowy Wierch) for which the pressure values at the levels of these stations were used and, based on them, only the trends of changes in this meteorological element were determined. In addition, a series of measurements from the Scientific Station of the Climatology Department of the Jagiellonian University in Krakow for the years 1901–2018 was used. Annual, seasonal, and monthly pressure values, as well as the variability of the number of days with a pressure ≤ 990 hPa or ≥ 1030 hPa were characterised. The study confirmed the latitudinal distribution of pressure values and the small range of their changes in the average values, especially in the warm half-year. The highest pressure values occurred in the south and south-east of the country, while the lowest along the Baltic Sea coast. It was also determined that during analysed periods (1966–2018 and 1901–2018) no tendency was found in long-term variability of pressure values (both in annual and seasonal, as well as monthly values). The analysis revealed that strong high-pressure systems (SLP ≥ 1030 hPa) over Poland occur several times more often than deep lows (SLP ≤ 990 hPa). Although the frequency of their occurrence differs depending on the region of Poland. The conducted studies have shown that the long-term variability in the number of days with SLP ≤ 990 hPa and SLP ≥ 1030 hPa do not show a clear trend. At the same time, the occurrence of fairly regular, several-year periods of increased pressure values and number of days analysed is a characteristic feature of pressure changes in Poland.