Droughts in the area of Poland in recent centuries

Abstract

Abstract. The paper presents the main features of droughts in Poland in recent centuries, including their frequency of occurrence, coverage, duration and intensity. For this purpose both proxy data (documentary and dendrochronological) and instrumental measurements of precipitation were used. The reconstructions of droughts based on all the mentioned sources of data covered the period 996–2015. Examples of megadroughts were also chosen using documentary evidence, and some of them were described. Various documentary sources have been used to identify droughts in the area of Poland in period 1451–1800 and to estimate their intensity, spatial coverage and duration. Twenty-two local chronologies of trees (pine, oak, and fir) from Poland were taken into account for detecting negative pointer years (exceptionally narrow rings). The longest chronology covers the years 996–1986 and was constructed for eastern Pomerania. The delimitation of droughts based on instrumental data (eight long-term precipitation series) was conducted using two independent approaches. In the first approach we used the globally and nationally popular Standard Precipitation Index (SPI), which was calculated for 1-, 3-, and 24-month time scales. Thus, three categories of droughts were analysed: meteorological (SPI1), agricultural (SPI3) and hydrological (SPI24). For delimitation of droughts (dry months), the criteria used were those proposed by McKee (1993) and modified for the climate conditions of Poland by Łabędzki (2007). Droughts were divided into three categories based on the following SPI values: moderate droughts (−0.50 to −1.49), severe (−1.50 to −1.99), and extreme (≤−2.00). The second approach includes the new proposed method for distinguishing droughts and quantitatively estimating their intensity and duration. More than one hundred droughts were found in documentary sources from the mid-15th century to the end of the 18th century, including 17 megadroughts. A greater-than-average number of droughts was observed in the second halves of the 17th century, and of the 18th century in particular. Dendrochronological data confirmed this general tendency in the mentioned period. The clearly greatest number of negative pointer years occurred in the 18th century and then in the period 1451–1500. In the period 996–2015, a total of 758 negative pointer years were recorded. Analysis of SPI (including its lowest values, i.e. droughts) showed that the long-term frequency of droughts in Poland has been stable in the last two or three centuries. Extreme and severe droughts were most frequent in the coastal part of Poland and in Silesia. Most droughts had a duration of two months (about 60–70 %), or 3–4 months (10–20 %). Frequencies of droughts with a duration of 5 and more months were lower than 10 %. The longest droughts had a duration of 7–8 months. The frequency of droughts of all categories in Poland in the period 1722–2015 was greatest in winter. This fact should be taken into account when analysing droughts delimited using documentary evidence. In Poland in 1451–1800, in light of this sort of information, droughts in spring and summer clearly dominated, while only three winter droughts were mentioned. The occurrence of negative pointer years (a good proxy for droughts) was compared with droughts delimited based on documentary and instrumental data. A good correspondence was found between the timing of occurrence of droughts identified using all three kinds of data (sources).

Global Sensitivity Analysis of the Standardized Precipitation Evapotranspiration Index at Different Time Scales in Jilin Province, China

“…In addition, Zhang et al [33], using the self-calibrating Palmer Drought Severity Index, confirmed our findings, and concluded that the sensitivity of precipitation was higher than that of ET o . Our finding, the high contribution rate of P, would also be a potential evidence and explanation as to why the P-based indices like the SPI show a high level of consistency with the SPEI, and a considerable adaptability in most times and places, such as the findings of Yao et al [34], Wang et al [57], Chen et al [8], and Przybylak et al [30].…”

“…The SPEI at the 1 to 6 month time scale is most appropriate to monitor drought impacts with regard to meteorological and agroecological systems, while the SPEI at the 7 to 18 month time scale is appropriate for the drought identification for hydrological systems [8,9,63]. Some other authors also report that 1, 3, and 24 month time scales are used as a good proxy for meteorological, agricultural, and hydrological [30].…”

“…It is able to analyze the main role of meteorological variables in regional ET o assessments [29]. Thus, sensitivity analysis of drought indices to meteorological variables can be applied to analyze the relationship between meteorological variables and drought events [30]. In recent years, the PM equation has been widely used in the sensitivity analysis of ET o [31][32][33].…”

Water Quality and Ichthyofauna Habitat Conditions in Lake Czolnowskie (N-W Poland)

“…Increase in human population on Earth (with accompanying increase in water demand), increasing intensification of agriculture [7,8], as well as disturbing climatic changes observed in recent years, i.e. global warming and drought [9], significantly inhibit rational management of available resources of water in Poland, which status, due to multiple indicators (e.g. oxygen, fluorides, biogenic substances) being exceeded, is considered as bad [10].…”