Droughts in the area of Poland in recent centuries in the light of multi-proxy data

Abstract

The history of drought occurrence in Poland criteria used were those proposed by McKee et al. (1993) and in the last millennium is poorly known. To improve this modified for the climate conditions of Poland by Lab˛edzki knowledge we have conducted a comprehensive analysis us (2007). ing both proxy data (documentary and dendrochronological) More than 100 droughts were found in documen and instrumental measurements of precipitation. The paper tary sources in the period 1451–1800, including 17 presents the main features of droughts in Poland in recent megadroughts. A greater than average number of droughts centuries, including their frequency of occurrence, cover were observed in the second halves of the 17th century and age, duration, and intensity. The reconstructions of droughts the 18th century in particular. Dendrochronological data con based on all the mentioned sources of data covered the pe firmed this general tendency in the mentioned period. riod 996–2015. Examples of megadroughts were also cho Analysis of SPI (including its lowest values, i.e. droughts) sen using documentary evidence, and some of them were de showed that the long-term frequency of droughts in Poland scribed. has been stable in the last two or three centuries. Extreme Various documentary sources have been used to identify and severe droughts were most frequent in the coastal part droughts in the area of Poland in the period 1451–1800 and of Poland and in Silesia. Most droughts had a duration of 2 to estimate their intensity, spatial coverage, and duration. months (about 60 %–70 %) or 3–4 months (10 %–20 %). Fre Twenty-two local chronologies of trees (pine, oak, and fir quencies of droughts with a duration of 5-or-more months from Poland were taken into account for detecting nega were lower than 10 %. The frequency of droughts of all cat tive pointer years (exceptionally narrow rings). The delimita egories in Poland in the instrumental period 1722–2015 was tion of droughts based on instrumental data (eight long-term greatest in winter, while in the documentary evidence (1451– precipitation series) was conducted using two independent 1800) droughts in this season are rarely mentioned. approaches (Standard Precipitation Index, SPI, calculated for The occurrence of negative pointer years (a good proxy for 1-, 3-, and 24-month timescales, and a new method proposed droughts) was compared with droughts delimited based on by authors). For delimitation of droughts (dry months), the documentary and instrumental data. A good correspondence was found between the timing of occurrence of droughts identified using all three kinds of data (sources).