Influence of teleconnection patterns on precipitation variability and on river flow regimes in the Miño River basin (NW Iberian Peninsula)

The influence of the most representative winter patterns of atmospheric variation in the Northern Hemisphere on precipitation variability and on river flow regimes was evaluated for the Miño River basin (NW Iberian Peninsula). The Arctic Oscillation (AO) was also considered in order to analyze the effect of a larger-scale atmospheric mode on precipitation and river flow. Precipitation data were obtained from 22 rain-gauge stations located within the Miño River basin from 1976 to 1997, and the Miño River flow data were recorded at Frieira gauge station from 1970 to 2005. Both hydrological-year (October to September) time series were averaged for the wet season (December to February). The precipitation variability and river flow in the Miño catchment were shown to have high positive correlation. Relationships with atmospheric circulation modes show that the main precipitation variability, and consequently the river-flow regimes, during winter cannot be explained by a single atmospheric pattern. The temporal evolution (1970–2005) of the correlation between the teleconnection indices and river flow averaged for 22 yr periods showed how all atmospheric patterns evolve with a different trend structure—in such a way that the most prevalent pattern depends on the chosen period of time. Moreover, the time evolution of the correlation between the AO and river flow remains more stationary than for the rest of the indices, due to its larger scale.