Mesoscale precipitation variability in the region of the European Alps during the 20th century

Abstract

The purpose of this study is to construct and evaluate a new gridded analysis of precipitation that covers the entire region of the European Alps (43.2-48.8°N, 3.2-16.2°E), resolves the most prominent mesoscale variations (grid spacing 25 km) and extends with a monthly time-resolution over most of the 20th century . The analysis is based on a reconstruction using the reduced-space optimal interpolation technique. It combines data from a high-resolution network over a restricted time period (1971-90) with homogeneous centennial records from a sparse sample of stations. The reconstructed fields account for 78% of the total variance in a cross-validation with independent data. The explained variance for individual grid points varies between 60 and 95%, with lower skills over the southern and western parts of the domain. For averages over 100 × 100 km 2 subdomains, the explained variance increases to 90-99%. Comparison of the reconstruction with the CRU05 global analysis reveals good agreement with respect to the interannual variations of large subdomain averages (10 000-50 000 km 2 ), some differences in decadal variations, especially for recent decades, and physically more plausible spatial patterns in the present analysis.The new dataset is exploited to depict 20th century precipitation variations and their correlations with the North Atlantic oscillation (NAO). A linear trend analysis (1901-90) reveals an increase of winter precipitation by 20-30% per 100 years in the western part of the Alps, and a decrease of autumn precipitation by 20-40% to the south of the main ridge. Correlations with the NAO index (NAOI) are weak and highly intermittent to the north and weak and more robust to the south of the main Alpine crest, indicating that changes in the NAOI in recent decades are not of primary importance in explaining observed precipitation changes.

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

“…7). These results contrast with those obtained by other authors (Haylock and Goodess, 2004;Quadrelli et al, 2001;Schmidli et al, 2002) who find trends in alpine precipitation over generally large areas. The differences can be presumably ascribed to the different length of the rainfall records and to the methods that are used.…”

“…For example Quadrelli et al (2001) investigate the winter precipitation variability for the period 1971-1992 and find significant relationship between rainfall and NAO; Beniston and Jungo (2002) detect clear links between strongly positive and negative modes of the NAO and extremes of moisture, temperature and pressure, especially for high elevation sites; Schmidli et al (2002) detect only weak and highly intermittent correlations between winter alpine precipitation for the period 1901-1990 and the North Atlantic Oscillation Index. Not all these studies use spatially extended climatic records and in some cases only relatively short series are used (e.g., Quadrelli et al, 2001).…”

A new instrumental precipitation dataset for the greater alpine region for the period 1800-2002

“…So, although national studies can achieve better data quality (where data homogenization is based on a higher density of stations and detailed station histories) they are artificially limited by national borders that do not necessarily coincide with coherent climatic regions. The first steps in creating supra-national precipitation datasets for the Alps and their surroundings had been taken, for example, by Schmidli et al (2001Schmidli et al ( , 2002. They concentrated on data collection and analysis and worked with samples of 20 to 100 years.…”

Trends in Swiss Alpine snow days: The role of local‐ and large‐scale climate variability

“…Large-scale upper air fields such as pressure and stratospheric ozone are rather strongly forced by the NAO variability [Appenzeller et al, 2000;Beniston, 1997]. Surface and possibly smaller scale variables such as precipitation seem to be dominated by other modes on the seasonal to interannual time scale [Massacand and Davies, 2001;Schmidli et al, 2002].…”