Abstract
The influence of large-scale climate variability on winter river discharge and precipitation across western Europe is investigated. We analyze 60 years of monthly precipitation and river flow data from 18 major western-European rivers and its relationship with dominant teleconnection patterns and climate indices in this region. Results show that winter river flow is characterized by large interannual variability, best correlates with (a) the North Atlantic Oscillation (NAO) at the far-northern (R up to 0.56) and southern latitudes (R up to −0.72), and (b) the West Europe Pressure Anomaly (WEPA) at the middle and northern latitudes, from 42° N to 55° N (R up to 0.83). These indices also explain the interannual variability in autumn and spring discharge in rivers characterized by secondary floods. Compared to the other leading modes of atmospheric variability, WEPA increases the correlations with winter precipitation up to 0.8 in many regions of western and central Europe. A positive WEPA corresponds to a southward shift and an intensification of the Icelandic-Low/Azores-High dipole, driving enhanced precipitation and river discharge in these regions. The correlations with precipitation are slightly higher than those with river discharge, particularly in France, with clear latitudinal gradient. This trend suggests that water storage variability and other catchment characteristics may also influence the interannual variability of river discharge. Seasonal forecasting of the WEPA and NAO winter indices can become a powerful tool in anticipating hydrological risks in this region.
Highlights
1lists liststhe themain maincharacteristics characteristicsofofthe theriver riverbasins, basins,the thegauges gauges used used in in this this study study and the winter mean (DJFM) river discharge
West Europe Pressure Anomaly (WEPA) index consistently showed the highest correlation with winter river discharge for the English, Welsh, and French rivers (Table 2)
The correlation with WEPA was strong for rivers in the middle and south of the UK, with R > 0.72; the correlation was significant (p < 0.01)
Summary
The variations in water resources and hydrological variables on timescales of years to decades has become a critical issue because of water scarcity and the growth of global water demand [1,2] In this context, it is essential to link local river streamflows with large-scale climate patterns of oceanographic and atmospheric variability; this is critical to predicting the evolution of the hydrological and ecological functioning of rivers [3], and to improving the management of water resources and hydrological hazards [4,5]. Discharge records for major rivers around the world show multidecadal fluctuations linked to such large-scale climate patterns (review in [7]). Chiew and McMahon [13] found a strong and consistent ENSO-discharge teleconnection in Australia and New Zealand, and Central and
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