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

Abstract

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 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. KEY WORDS: Teleconnection indices · Arctic Oscillation · Precipitation · River flow · Iberian Peninsula Resale or republication not permitted without written consent of the publisherClim Res 32: [63][64][65][66][67][68][69][70][71][72][73] 2006 respondence between precipitation and the dominant pattern of atmospheric-circulation variability in the North Atlantic, the North Atlantic Oscillation (NAO) (Wallace & Gutzler 1981). Thompson & Wallace (1998) introduced the hypothesis that the NAO is the local manifestation of a global pattern called the Arctic Oscillation (AO). This AO is the result of the coupling between the stratospheric polar vortex and tropospheric circulation. Previous research has found a strong correlation between the strength of the polar stratospheric vortex and geopotential anomalies in the middle troposphere in the Northern Hemisphere and that the structure is produced specifically with the NAO pattern. In a later study, Thompson & Wallace (2000) found that variation in the North Hemispheric polar vortex is stronger in wintertime, and that this is the season when the correlation with the NAO is larger. In this manner, the correlation between the NAO and rainfall or the NAO and river flow in winter could be considered as a consequence of the variations of a hemispheric variation mode (AO). In addition, Rodríguez-Puebla et al. (1998) identified 4 regional precipitation regimes on the IP associated with the following large-scale atmospheric patterns at the monthly time scale: NAO index; East Atlantic (EA); Southern Oscillation Index (SOI) and Scandinavia (SCAN...

Links between circulation weather types and teleconnection patterns and their influence on precipitation patterns in Galicia (NW Spain)

“…Other teleconnection patterns that appear in the Northern Hemisphere (Barnston and Livezey, 1987) are the Scandinavian Pattern (SCA), the Polar/Eurasia Pattern (POL), the EA, and the (EA/WR). The NAO is the most important one in our area, but the EA, EA/WR and SCA are also significant - Taboada, 2005 andDeCastro et al, 2006, found that winter rainfall in Galicia is explained mainly by four indices (NAO, EA, EA/WR and SCA). The influence of four different indices, three representing north-south dipoles and another representing an east-west dipole, means that Galicia is located in an area that is subject to a wide variety of influences (Figure 2).…”

“…The storm track in this area depends strongly on the North Atlantic Oscillation (NAO) (Trigo, 2006). Other teleconnection patterns, such as the Scandinavian Pattern (SCA) or the Eastern Atlantic (EA) are also important for explaining variability in precipitation (Blackburn and Hoskins, 2001;Lorenzo and Taboada, 2005;DeCastro et al, 2006). It has been found that correlations between winter rainfall in Galicia and the NAO index have a value of −0.52, while correlations with other indices are lower, but significant.…”

“…The inter-annual variability of rainfall in Galicia can be related to variations in the atmospheric configuration in the Northern Hemisphere (Lorenzo and Taboada, 2005;DeCastro et al, 2006). Our study area lies in between the influence of several large Northern Hemisphere teleconnection patterns as shown in Figure 2.…”

Abrupt shifts in the Gironde fish community: an indicator of ecological changes in an estuarine ecosystem

“…The NAO influences wind intensity and direction, thus regulating quantities of precipitation over the North Atlantic (Hurrell 1995). The East Atlantic Pattern (EAP) index is similar to the NAO but relates to the subtropical area (Barnston & Livezey 1987, deCastro et al 2006). This index is an important element to consider because of its strong influence on the environment of western Europe and the French coast (Msadek & Frankignoul 2009).…”

The state of climate in NW Iberia

“…Other teleconnection patterns appearing in the North Atlantic and also affecting climate variability over the IP are the Scandinavian (SCAND), Eastern Atlantic (EA), and Eastern Atlantic-Western Russia (EA-WR) patterns, which increases the complexity of climate-change studies. Thus, recent studies have proved that atmospheric and oceanic phenomena such as precipitation, river discharge, and upwelling should be explained in terms of >1 teleconnection pattern (Lorenzo & Taboada 2005, deCastro et al 2006a.…”