Weather regimes and sea surge variations over the Gulf of Lions (French Mediterranean coast) during the 20th century

Abstract

Hourly sea surge variations observed at three tide-gauge stations (Grau-de-la-Dent(GD) located in the Rhône Delta, Sète(SE), and Port-Vendres(PV)) around the Gulf of Lions are strongly correlated during the wintertime period (October to March) of 1986-1995. Relationships between the early morning (6 a.m. UTC) sea surge observed at Grau-de-la-Dent station and five weather regimes -Zonal (ZO), East-Atlantic (EA), Greenland Above (GA), Blocking (BL), and Atlantic Ridge (AR) -over the northeast Atlantic and Europe (40°W-40°E, 30°-70°N) are analysed during the wintertime period of 1905-2002. More than 75% of sea surges ≥ 40 cm occur during both of the weather regimes associated with a negative North Atlantic Oscillation(NAO) phase (41.2 and 34% during BL and GA weather regimes, respectively), ahead of low pressure travelling usually southeastward, on a stormtrack shifted south of 55°N. The relationships between monthly/seasonal frequency of weather regime and 75th percentile of sea surge at GD tend to strengthen during the 20th century: for example, correlation between seasonal frequencies of GA and 75th percentile of sea surge increases from 0.07 (not significant) in 1905-40 to 0.83 (signifiicant at the one-sided 99% level) in 1974-2002.

Statistical modeling of interannual shoreline change driven by North Atlantic climate variability spanning 2000–2014 in the Bay of Biscay

“…Thus, the statistically significant relationships identified here may be related to weather regime-driven modulation of incoming wave energy. Change in water level induced by weather regime-driven variations of sea-level pressure (Barrier et al 2013) and/or onshore winds (Ullmann and Moron 2008;Ullmann and Monbaliu 2010) may also impact shoreline change as storm wave events coinciding with higher water levels result in higher rates of erosion (Ruggiero et al 2001;Serafin and Ruggiero 2014). However, this was not verified here as it is beyond the scope of this study.…”

Weather Regimes in the Euro-Atlantic and Mediterranean Sector, and Relationship with West African Rainfall over the 1989–2008 Period from a Self-Organizing Maps Approach

“…The mean months of the occurrence together with the frequency of occurrence over the season are displayed for each WR. Let us recall that four winter North Atlantic weather regimes have been described in the literature (Vautard, 1990;Moron et al, 2003;Cassou et al, 2004a;Ullmann and Moron, 2007;SanchezGomez et al, 2008, among Finally, (iv) the Greenland Anticyclone pattern (negative phase of the NAO) dominated by a strong positive anomaly centered over western Greenland. The NAO pattern is also found in 10 summer season by empirical orthogonal function and cluster analyses.…”

Cambios en la frecuencia de los Regímenes de Tiempo sobre la región Euro-Atlántica y Mediterránea y su relación con las temperaturas anómalas sobre el Mar Mediterráneo

“…We have tested with the Reanalysis data by computing the WR from ERA-40 data with 5-days means SLP for the summer season and with another clustering method (k-means, see Michelangeli et al, 1995;Ullmann and Moron, 2007). The 4 main patterns (figure 6) are consistent with the most frequent patterns described in ERA-interim (Polo et al, 2011).…”

“…Low frequency variability can be interpreted as a change in amplitude/frequency of the WRs or in the transitions between them (Ghil and Robertson 2002;Cassou et al, 2004). Most of the works characterizing the WR over the North Atlantic-Europe region are based in the boreal winter season finding that four main WRs can be defined by Sea Level Pressure (SLP) as: positive NAO or zonal regime, negative NAO or Greenland anticyclone, Blocking regime with anomalous high over Scandinavia and Atlantic ridge, with positive anomaly over North Atlantic and negative over Northern Europe (Cassou et al, 2004;Ullmann and Moron, 2007). Similar WRs have been found in boreal summer (Fereday et al, 2008).…”