Odpływ rzek w Polsce w różnych fazach oscylacji północnoatlantyckiej
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Date
2010
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Wydawnictwo Poznańskiego Towarzystwa Przyjaciół Nauk
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Abstract
Deviations of climatic elements from average levels, like those caused by changes in the atmosphe-
ric circulation, modify the conditions in which the river runoff forms. The river regime is controlled by both,
precipitation and air temperature, whose magnitudes show a significant dependence on the intensity of zonal
circulation. A simple indicator characterising the atmospheric circulation over the north Atlantic is the North
Atlantic Oscillation Index (henceforth, NAO). The North Atlantic Oscillation is considered a very important
climate-forming factor in Poland.
The analysis embraced monthly, seasonal and annual runoff of Polish rivers taking into consideration
Hurrell’s winter NAO index from the years 1951–2000. The analysed flow series came from 141 profiles loca-
ted on 86 Polish rivers. The selected rivers are distributed evenly throughout Poland and represent a diversity
of environmental conditions (Fig. 1).
The aim of the present research was to examine the extent to which the North Atlantic Oscillation affects
the runoff of Polish rivers: its seasonal structure and spatial variability. Differences were calculated between
the monthly, seasonal and annual runoff observed in the years with exceptionally high (NAODJFM > 2) and
low (NAODJFM < –2) values of the winter NAO index and their statistical significance was determined. Also
calculated were monthly, seasonal and annual deviations of runoff in the years with high NAODJFM indices
from that in the years with their low values (assuming the runoff in the years with low NAODJFM indices to
be 100%).
The research results have confirmed a strong effect of the North Atlantic Oscillation on the runoff volume
of the Polish rivers. In the winter months – January, February and March, the most statistically significant
positive relations can be observed on rivers in the north-east and north of the country. The river runoff in those
regions in a positive NAO stage is then more than 200% higher than in a negative stage. In the spring months,
in April hold for the runoff of rivers in north-eastern Poland and the middle parts of the Oder and Warta basins,
and in May, rivers of almost the entire country with the exception of the east and south-east. In those areas stre-
amflow in a negative NAO stage is more than 50% higher in a positive NAO stage. The obtained results show
that the North Atlantic Oscillation has the greatest effect on streamflow in the winter-spring months, i.e. in the
period when the most abundant water resources are being formed in Poland. Hence, in a positive NAO stage,
one might expect a considerable buildup of the water resources in the winter months, mostly in the north-east,
and their marked dwindling almost throughout the entire country in spring.
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Keywords
North Atlantic Oscillation,, River runoff, Statistical significance of the difference (T-test)
Citation
Badania Fizjograficzne, Seria A, Tom 61, 2010, s. 129-144
ISBN
978-83-7654-010-8