Investigating possible links between the North Atlantic Oscillation and rainfall variability in northwestern France over the past 35 years

Abstract

[1] In this paper, the temporal dynamics of precipitation in northwestern France in relation to the dominant climatic pattern in Europe were investigated. The general trends and the nonstationary behavior of the North Atlantic Oscillation (NAO) were described using fractal analysis and Fourier spectral and continuous wavelet analysis of a NAO index time series over the 1865-2004 period. The 44-year and 8-year multidecadal components showed a clear increasing power during the second half of the last century. The possible link between rainfall variability and the NAO was then investigated. The links between the NAO and rainfall were not as obvious, as NAO-like components were not easily retrieved in the precipitation records: Relationships between the NAO and rainfall were very likely at certain timescales but were not systematically very obvious. For instance, the characteristic quasi-biennal oscillation (QBO) of the NAO was barely detected in precipitation, but a %6-year fluctuation beginning in the 90s was found to be statistically significant at a 95% confidence limit After investigating a possible link with the Southern Oscillation Index, the occurrence of this fluctuation in the beginning of the 90s could be related to the observed shift of the QBO toward slightly higher frequencies in the NAO time series. On the other hand, a modulation of the QBO by a %6-year interannual fluctuation would suggest the existence of a %6-year climate pattern that could affect precipitation and, to a lesser extent, the NAO. Cross-wavelet analysis between the NAO and precipitation revealed a loss in correlation across the 1970-2005 period, which seemed to be the fact of a QBO-like fluctuation. This loss of correlation was related to the above-mentioned shift of the QBO and 6-year rainfall interannual band since the 90s.

Characterization of the Interannual Variability of Precipitation and Streamflow in Tensift and Ksob Basins (Morocco) and Links with the NAO

“…The wavelet transformation is used to follow the time course of the process at different scales in the signal [57]. It has been used for numerous studies in geosciences (e.g., [13,58,59]). In particular, applications of wavelets to discharge time series allow describing signals of climatic oscillation [14,16,60,61].…”

“…Many studies have been carried out in order to determine the relationship between NAO and hydrological parameters [13][14][15][16]. They show the NAO contribution in the eight-year band falling on the second half of the last century.…”

Links between multidecadal and interdecadal climatic oscillations in the North Atlantic and regional climate variability of northern France and England since the 17th century

“…On the Atlantic basin, the multidecadal variability of the sea surface temperatures (SSTs) refers to the Atlantic Multidecadal Oscillation (AMO) [Enfield et al, 2001;Knight et al, 2006]. In addition, the North Atlantic Oscillation (NAO) exhibits strong variability without presenting, contrary to the AMO, any characteristic time scales; however, it can be noted that the end of the 20th century was dominated by decadal fluctuations [Hurrell, 1995;Wanner et al, 2001;Massei et al, 2007]. Nevertheless, although the present study does not aim to explore such interactions, we will note that the multidecadal variability could be internal to the ocean-atmosphere interactions [Schelsinger and Ramankutty, 1994;Higuchi et al, 1999;Enfield et al, 2001].…”

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.…”

“…They could not establish a relationship between the NAO and El Niño-Southern Oscillation (ENSO) and snow cover in the French Alps and Pyrenees. Massei et al (2007) used continuous wavelet transforms of seven precipitation time series and compared them with NAO wavelet transforms. They could not establish a link between NAO and rainfall as precipitation records did not contain easily retrievable NAO-like components in northwestern France.…”