Abstract
The decadal oscillation of rainfall in Europe that has been observed since the end of the 20th century is a phenomenon well known to climatologists. Consequences are considerable because the succession of wet or dry years produces floods or, inversely, droughts. Moreover, much research has tried to answer the question about the possible link between the frequency and the intensity of extra-tropical cyclones, which are particularly devastating, and global warming. This work aims at providing an exhaustive description of the rainfall oscillation in the 5–10 year band during one century on a planetary scale. It is shown that the rainfall oscillation results from baroclinic instabilities over the oceans. For that, a joint analysis of the amplitude and the phase of sea surface temperature anomalies and rainfall anomalies is performed, which discloses the mechanisms leading to the alternation of high and low atmospheric pressure systems. For a prospective purpose, some milestones are suggested on a possible link with very long-period Rossby waves in the oceans.
Highlights
The succession of wet and dry periods over decadal cycles that occur in some areas is a well-known phenomenon
The cross-wavelet power and the coherence phase of reduced rainfall height (RRH), scale-averaged over the 5–10 year band, time-averaged over the entire observation period, allows representing well delimited regions where the rainfall oscillation occurs in the 5–10 year band (Figure 2)
Within the tropical belt all continents are subject to the rainfall oscillation in the 5–10 year band
Summary
The succession of wet and dry periods over decadal cycles that occur in some areas is a well-known phenomenon. Authors paid a particular attention to the quasi-decadal oscillation of rainfall in Europe that has been observed since the end of the 20th century This phenomenon has been reported in abundant literature [1,2,3], with authors relating studies carried out in Mediterranean areas [4,5], in the Iberian Peninsula [6,7,8,9,10,11,12,13,14], in Italy [15,16], in the UK [17,18], in Ireland [19] and in France [20,21,22]. The other regions subject to this alternation are less well documented likely because the rainfall oscillation has occurred during previous decades and is not no longer active presently
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