Extreme temperatures and precipitation in Poland - an evaluation attempt

Summer (JJA) and winter (DJF) temperature extremes and summer (JJA) precipitation extremes in Poland that occurred in the years 1951-2006 are analyzed in this paper. Diurnal extreme values of air temperature (Tmax, Tmin) and diurnal precipitation totals (P) are considered. The data was obtained from 54 meteorological stations. Extreme values were identified based on different methodological approaches. Advantages and disadvantages of selected methods are shown with respect to both temporal and spatial variability of the data. The differences obtained as a result of the applied criteria confirm that the method of percentiles seems to be the most suitable one to be used in spatial analysis. This is especially relevant in areas with a relatively high variability of absolute values. When it comes to analyses of multi-annual trends, the criterion used plays a less significant role. Regardless of the method, there is a certain direction of changes that is maintained, although their magnitudes may be different. It may be concluded from the conducted analyses that for the full evaluation of both spatial variability and temporal variability of weather extremes, a variety of methods and criteria for identifying extreme values, should be considered. They may significantly influence the final results.