Interannual variability of winter precipitation in the European Alps: relations with the North Atlantic Oscillation

Abstract

Abstract. The European Alps rely on winter precipitation for various needs in terms of hydropower and other water uses. Major European rivers originate from the Alps and rely on winter precipitation and the consequent spring snow melt for their summer base flows. Understanding the fluctuations in winter rainfall in this region is crucially important to the study of changes in hydrologic regime in streams and rivers, as well as to the management of their water resources. Despite the recognized relevance of winter precipitation to the water resources of the Alps and surrounding regions, the magnitude and mechanistic explanation of interannual precipitation variability in the Alpine region remain unclear and poorly investigated. Here we use gridded precipitation data from the CRU TS 1.2 to study the interannual variability of winter alpine precipitation. We found that the Alps are the region with the highest interannual variability in winter precipitation in Europe. This variability cannot be completely explained by large scale climate patterns such as the AO, NAO or the EA-WR, even though regions below and above the Alps demonstrate connections with these patterns. Significant trends were detected only in small areas within this region, and were of opposite sign between the eastern and western part of the Alps.

Interannual variability of winter precipitation in the European Alps: relations with the North Atlantic Oscillation.

“…Considering how the grid data are used in this paper, it is particularly important that the comparison between the annual and seasonal coefficients of variation of station and grid precipitation records comes out more than acceptable. This demonstrates that interannual variability of precipitation in the CRU TS 1.2 is comparable to that measured by the rainfall stations (Table 1) and confirms the good temporal agreement found by Bartolini (2007) between grid and station time series.…”

“…To assess the influence of the extreme NAO phases on precipitation events, we have calculated the Spearman's rank correlation eliminating from the NAOI and SPI time series the years with NAOI values in the range (−1, 1). The spatial distribution of these correlation coefficients, that can be found in Bartolini (2007), exhibits patterns similar to those in Fig. 5 but with slightly higher values, demonstrating that the stronger phases of the NAO have a significant effect on the European climate, even though the result on the Alps does not change.…”

“…Although mountainous areas are known for the relatively strong variability of their rainfall regimes, presumably due to orographic effects on local climate patterns, the relation between the interannual variability of precipitation and elevation remains unclear (Chacon and Fernandez, 1985). In fact, previous studies on the same data set (Bartolini, 2007) have shown that the relatively strong interannual variability observed in the Alps does not depend on the mean elevation of the grid cell or the mean winter precipitation. We have then investigated the influence of external forcings, such as the large-scale patterns of climate variability (NAO, AO, and EA/WR) on the climate of the alpine region, comparing monthly precipitation and SPI time series to indices representing the strength of these climate patterns.…”

“…1c) and a consistent bias (Table 1). In addition, a trend analysis is made for the corresponding grid and station records, showing that no significant trends exist for both the set of data, except for a weak discrepancy found in Trento and Sonnblick (see Bartolini (2007) for more details). Considering how the grid data are used in this paper, it is particularly important that the comparison between the annual and seasonal coefficients of variation of station and grid precipitation records comes out more than acceptable.…”

Atlantic Ocean sea-surface temperatures and regional streamflow variability in the Adour-Garonne basin, France

“…streamflow, precipitation and snowpack) (Cayan and Peterson 1989, Cayan and Webb 1992, Kahya and Dracup 1993, Gershunov 1998, Cayan et al 1999, Enfield et al 2001, McCabe and Dettinger 2002, Rogers and Coleman 2003, Tootle et al 2005, Hunter et al 2006, as well as European hydrology (Rodwell et al 1999, Gallego et al 2005, Massei et al 2007, Lopez-Bustins et al 2008, Bartolini et al 2009, Jacobeit et al 2009, Lavers et al 2010, Brandimarte et al 2011. The papers cited above represent a small number of the many research studies conducted in the area.…”