Influence on Europe
While there may be some correlations between El Niño and the precipitation regime in Europe, this teleconnection is only very weakly manifested. As a rule, precipitation behaviour in Europe is predominantly controlled by the so-called North Atlantic Oscillation (NAO).
The NAO characterises the pressure fluctuations in the North Atlantic atmosphere. The term oscillation indicates that the North Atlantic atmosphere switches between two states, namely that of a weak south-north pressure gradient to that of a strong south-north pressure gradient. The south-north pressure gradient over the North Atlantic governs the atmospheric flow regime over Europe and consequently also the migration paths of the precipitation-bearing disturbance zones.
When the NAO conditions are neutral, the influence of El Niño becomes more apparent in Europe. According to a report by the German Meteorological Service, more precipitation can be expected in winter in these circumstances, especially along the French Alps and the Jura Mountains and as far as southwest Germany. Large areas of Europe, however, remain unaffected by El Niño.
The name El Niño
El Niño (Spanish for “the boy, the child”, and symbolic of the Christ Child), got its name from Peruvian fishermen, who were often distressed by the unusually pronounced warming of the sea, which often reaches its peak around Christmas time. Fish populations reduce drastically because of the poor nutrient content of the warm water during an El Niño event, which, in former times at least, would have had devastating consequences for the fishing industry. Originally, it was only the warm ocean current that recurred at irregular intervals that was referred to as El Niño. When referring to the phenomenon as a whole, i.e. the reversal of atmospheric and oceanic circulation, the term ENSO was used. Nowadays, however, the terms El Niño and ENSO are often used interchangeably to refer to the phenomenon.