Estimation of local drought frequency in central Poland using the standardized precipitation index SPI

Poland is situated in a transitory temperate climate zone; nonetheless droughts occur, posing a serious economic, social and environmental problem. The central part has the lowest precipitation in the country, where frequent meteorological and agricultural droughts occur. To estimate meteorological drought frequency in the region, the SPI methodology is used. The analysis is made using the long-term record of precipitation from 1861 to 2005 for the Bydgoszcz area, at 3-, 6-, 12, 24- and 48-month timescales. The detailed characterization of chosen meteorological and agricultural droughts in 1991-2005 is presented in this paper. The results show that the frequency of months in which drought was identified at 3-, 6-, 12-, 24- and 48-month time scales, is about 30%. According to the equation as proposed in this study, the number of droughts of different duration in 100 years statistically is from 8 for the 48-month drought to 120 for the 3-month drought. On the basis of the analysis of the meteorological and agriculture drought in 2000, it has been shown that the 1-3 month SPI better reflects agricultural drought development than the 6-month SPI. To better understand and characterize droughts in agricultural areas additional indices should be used for the evaluation impacts of meteorological drought. Other indices need to be investigated to form a system of indices giving the best evaluation of droughts in a given region. Copyright (c) 2007 John Wiley & Sons, Ltd.