Complex changes of extreme precipitation in the warming climate of Poland

Abstract

AbstractThis article examined changes in observed precipitation extremes in Poland in 1959–2018. The study period was divided into two parts: 1959–1988 and 1989–2018, in order to examine whether extreme events have changed with warming. The return intervals (2‐; 5‐; 10‐ and 15‐year) of maximum 24 hr precipitation for autumn for period 1989–2018 have shortened in reference to 1959–1988. Also during spring, return periods of 2‐, 5‐ and 10‐year have decreased, while for winter: 10‐ and 15‐year return intervals have shortened. Exceedance analysis above the values of the 95th and 99th percentiles of precipitation during rainy days for the reference period 1971–2000 jointly with daily mean temperatures above 5°C was conducted in two ways. Using one threshold for all the temperature ranges, the number of days above the 95th (99th) percentile for years 1989–2018 was found to be lower (higher) than for 1959–1988. Examination of values above the highest percentiles for every temperature range separately indicated that the number of days above both percentiles decreased while the mean intensity increased for 1989–2018. Total precipitation amount above the 95th percentile decreased, but above the 99th percentile increased. Also, finally the sensitivity of precipitation to temperature was examined: the scaling factor was calculated on the basis of pairs of 99th percentile of precipitation and daily mean temperature above 5°C and results show higher values for the warmer period, 1989–2018 (6.06%/°C) in comparison to 1959–1988 (5.26%/°C). Also, the relationship of four indices of precipitation with annual mean temperature was obtained with rather negative results and association with annual dew point temperature, where positive values of the Pearson correlation dominated. The results obtained in this study indicate increases in more extreme precipitation, that is, in 99th more than in 95th percentile, along with the progressing global warming.