Impact of strong and extreme El Ni~nos on European hydroclimate

The question of European hydroclimate anomaly associated with El Niño-Southern Oscillation (ENSO) is revisited by composite analyses on data from Dai et al.’s Palmer Drought Severity Index, the Old World Drought Atlas (OWDA), and a 10-member CESM coupled-model Last Millennium Ensemble (CESM-LME) simulations. This study benefits from exceptionally long or large samples in OWDA and CESM-LME. The averagely strong El Niño (1–2 standard deviations, or about one event per decade) is correlated to wet condition in western and southern Europe, and dry condition in Northern Europe; this result agrees with previous studies and thus provides a further support to this scenario. We also find in OWDA that extremely strong El Niño (>2 standard deviation, or about one event every 70–100 years) is related to a dry condition in western Europe. This suggests that the extreme El Niño impact in western Europe is opposite, or at least not linear, to that for the averagely strong El Niño. The impact of extreme El Niño does not appear to be reproduced by the LME, and will require further analyses on other climate reconstructions and models data.