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

Hourly sea surge variations observed at three tide-gauge stations (Grau-de-la-Dent(GD) located in the Rhone Delta, Sete(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. Copyright © 2007 Royal Meteorological Society