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

E. Bartolini,P. Claps,P. D'Odorico

doi:10.5194/hess-13-17-2009

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 depend 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 river basins, 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 remains 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 explained by large scale climate patterns such as the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) or the East Atlantic/West Russia (EA/WR), even though regions below and above the Alps demonstrate connections with these patterns. Significant trends were detected only in small regions located in the Eastern part of the Alps.

Highlights

European Alps (43◦ N÷48◦ N, 5◦ E÷17◦ E) are characterized by a complex climatology, due to the orography, the geographical location and the interactions with the weather systems which move eastwards from the Atlantic Ocean
This variability cannot be explained by large scale climate patterns such as the Arctic Oscillation (AO), North Atlantic Oscillation (NAO) or the East Atlantic/West Russia (EA/WR), even though regions below and above the Alps demonstrate connections with these patterns
The map of the coefficient of variation (CV) of winter season precipitation across Europe is shown in Fig. 3, in which one can recognize that the Alps are a singular area of Europe, presenting, in the Eastern sector, coefficients of www.hydrol-earth-syst-sci.net/13/17/2009/

Summary

Introduction

European Alps (43◦ N÷48◦ N, 5◦ E÷17◦ E) are characterized by a complex climatology, due to the orography, the geographical location and the interactions with the weather systems which move eastwards from the Atlantic Ocean. Because of the vulnerability of the Alps to climate change (Beniston et al, 1997) and the contribution of these mountains to aquifer recharge and to the base flow of the main European rivers, it is important to understand the patterns and drivers of seasonal and interannual changes in precipitation This is especially true during the winter season, when most of the water storage accumulates in the snow pack. This study investigates fluctuations and trends in the interannual variability of precipitation and seeks for a relationship between monthly/seasonal precipitation and largescale patterns of atmospheric circulation To this end, we assess the strength and areas of influence of possible climatic teleconnections and investigate the specific role that the Alps play in the European climatology

Methods

Results

Conclusion