Changes of the hydrological regime of rivers of Northern and Central Europe in various periods of the North Atlantic Oscillation

Authors:

• Dariusz Wrzesiński

Abstract

The article presents the impact of the north Atlantic atmospheric circulation on the hydrological regimes o rivers of Northern and Central Europe. A river regime is defined as the type and temporal structure of streamflow in an average hydrological cycle. The elements of the structure include so-called hydrological periods, which were the instrument for the study of the regime as well as the basis of its characterisation and an assessment of its variability. Hydrological periods were determined via the grouping of elementary time units of the year (pentads) on the basis of the similarity of one of their features (the frequency distribution of the river discharge). The determination of hydrological periods was carried out on the basis of sets of 20 years with an extremely high and an extremely low NAO index, as well as 20-year periods from the 1901-2000 interval. The varying number and temporal structure of the hydrological periods thus distinguished allowed conclusions about differences in the variability of hydrological regimes of Scandinavian and Central European rivers in the various NAO circulation periods.