Regional and seasonal variability of extreme precipitation trends in southern Poland and central-eastern Germany 1951-2006

Spatial and temporal trend variability in extreme precipitation indices was studied for the meteorological seasons from 1951 to 2006. Eight indices were used, describing their frequency (90pNoD, 95pNoD), totals (1dayT, 5dayT, 90pT, 95pT) and intensity (90pInt, 95pInt). The following key challenges were addressed: (1) temporal variability in the relative number of stations with significant 30-year trends, (2) temporal stability and (3) average magnitude of the calculated 30-year trends. Temporal changes in the spatial extent of statistically significant extreme precipitation trends proceeded differently in each season. The trend direction, indicated by trend stability analysis, was consistent with that of averaged 30-year trend magnitudes at most stations. A distinct spatial differentiation emerged in the prevailing trend directions between the eastern and the western part of the study area. In all seasons, increasing trends in extreme precipitation dominated in central-eastern Germany, whereas opposite trends prevailed in southern Poland. This pattern was particularly prominent in winter. Similarities in the temporal variability of the percentage of significant trends between the eastern and the western sub-regions emerged in autumn only. Summer was characterized by the most pronounced temporal changes in the percentage of significant negative trends. Summer also showed the most stable extreme precipitation trends of all seasons and a higher trend magnitude than the transitional seasons. Spatial patterns of trend directions in spring, showing the most complex pattern of all seasons, vary depending on the index, particularly with respect to trend stability. Copyright (c) 2010 Royal Meteorological Society