European grosswetter during the warm and cold extremes of the El Niñco/Southern Oscillation

Abstract

El Niňo/Southern Oscillation (ENSO) warm and cold events affect the synoptic climatology of the north-eastern Atlantic-European sector. The classification of cyclonic and anticyclonic European Grosswetter (1881–1987) is analysed for its response on 26 warm and 21 cold ENSO episodes. Bi-monthly ranked composites computed over idealized 2–year ENSO warm (cold) episodes show more days of cyclonic (anticyclonic) steering over Europe. This signal is largest in the winter months of January and February following the year of a warm or cold event. The distributions of the occurrence of cyclonic and anticyclonic Grosswetter days are significantly different for warm and cold event winters: (i) there is more variability between individual warm event winter months, whereas the response to cold episodes is relatively uniform; (ii) on average, cyclonic Grosswetter days are experienced on 60 per cent (46 per cent) of the 58 warm (cold) event winter. days-about 70 per cent (90 per cent) of the warm (cold) event winters realize more than 30 (< 36) days of cyclonic steering. Qualitatively corresponding results are obtained at a representative central European location for sunshine duration and the sum of daily negative temperatures, which characterize the winter strength.