Title: Influence of solar forcing, climate variability and modes of low-frequency atmospheric variability on summer floods in Switzerland

Abstract

The higher frequency of severe flood events in Switzerland in recent decades has given fresh impetus to the study of flood patterns and their possible forcing mechanisms, particularly in mountain environments. This paper presents a new index of summer flood damage that considers severe and catastrophic summer floods in Switzerland between 1800 and 2009, and explores the influence of external forcings on flood frequencies. In addition, links between floods and low-frequency atmospheric variability patterns are examined. The flood damage index provides evidence that the 1817–1851, 1881–1927, 1977–1990 and 2005–present flood clusters occur mostly in phase with palaeoclimate proxies. The cross-spectral analysis documents that the periodicities detected in the coherency and phase spectra of 11 (Schwabe cycle) and 104 years (Gleissberg cycle) are related to a high frequency of flooding and solar activity minima, whereas the 22-year cyclicity detected (Hale cycle) is associated with solar activity maxima and a decrease in flood frequency. The analysis of low-frequency atmospheric variability modes shows that Switzerland lies close to the border of the principal summer mode. The Swiss river catchments situated on the centre and southern flank of the Alps are affected by atmospherically unstable areas defined by the positive phase of the pattern,more » while those basins located in the northern slope of the Alps are predominantly associated with the negative phase of the pattern. Furthermore, a change in the low-frequency atmospheric variability pattern related to the major floods occurred over the period from 1800 to 2009; the summer principal mode persists in the negative phase during the last cool pulses of the Little Ice Age (1817–1851 and 1881–1927 flood clusters), whereas the positive phases of the mode prevail during the warmer climate of the last 4 decades (flood clusters from 1977 to present).« less

Authors:

Peña, J. C.  ^[1];

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Schulte, L. ^[2]; Badoux, A. ^[3]; Barriendos, M. ^[4]; Barrera-Escoda, A. ^[1]

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+ Show Author Affiliations

1. Meteorological Service of Catalonia, Barcelona (Spain)
2. Univ. Autonoma de Barcelona (Spain). Dept. of Physical and Regional Geography, and Inst. Catalana de Recerca i Estudis Avancats (ICREA)
3. Swiss Federal Inst. for Forest, Snow and Landscape Research, Birmensdorf (Switzerland). Mountain Hydrology and Mass Movements Research Unit
4. Univ. of Barcelona, Barcelona (Spain). Dept. of Modern History, and Catalan Inst. of Climate Sciences (IC3)

Publication Date:

2015-09-10

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1565398

Resource Type:

Accepted Manuscript

Journal Name:

Hydrology and Earth System Sciences (Online)

Additional Journal Information:

Journal Name: Hydrology and Earth System Sciences (Online); Journal Volume: 19; Journal Issue: 9; Journal ID: ISSN 1607-7938

Publisher:

European Geosciences Union (EGU)

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Geology; Water Resources