Observed changes in precipitation totals in Poland

This paper examines observed changes in the indices of mean precipitation in Poland, based on daily precipitation records for 45 stations in Poland from 1961 to 2017. Changes in annual, semi-annual, seasonal, as well as monthly precipitation totals are examined. In addition, changes in the number of days with precipitation (≥ 1 mm), as well as in the Simple Daily Intensity Index and the ratio of precipitation in the warm half-year to precipitation in the cold half-year are studied. Many changes are detected, but most of them are not statistically significant at the 0.1 level. Yet, there are regionally consistent seasonal changes, with a dominating clear precipitation increase in spring and winter. The Student’s t-test for the comparison of means for two intervals: 1961–1990 and 1991–2017 revealed statistically significant increases for annual and spring precipitation, as well as for Simple Daily Intensity Index, and monthly data: increases for February, March, July, September, October and decreases for: June, August, November, December.