14 DAY TRIAL // When El Ni?o begins, the deserts of the Peruvian coasts are turned to lakes, but worldwide there are great floods, violent cyclones and severe droughts that trigger hunger, epidemics, huge wildfires, and damages on crops, goods and environment.
El Nino is the warm oceanic current which emerges off the Peruvian coasts every 2 to 7 years. Because the warm current appears usually around Christmas, the old Spanish sailors named it El Ni?o ("the Baby" in Spanish, alluding to Jesus).
In Peru, warming means higher rainfalls and larger herds. But the warm layer impedes the colder waters bellow, rich in nutrients, to get up. In this case, sea productivity drops, and many sea birds migrate.
El Ni?o emerges because of the water movements in the Pacific. When the sun warms the waters in the Western Pacific (off Indonesia and Australia), the wet hot air rises, generating an area of low pressure. The climbing air mass cools down, forming water vapors that generate rains in that region.
The dried air is pushed eastwards by the winds in the upper atmosphere. Moving eastwards, the air mass cools further, becoming heavier and above Ecuador it starts descending.
This determines the appearance of a high pressure zone. At lower altitudes, the tradewinds move back westwards, to Indonesia, ending the cycle. The tradewinds act like a breeze, pushing the hot air towards western Pacific, so the sea level here is 60 cm higher and the waters are 8 degrees C warmer. In the eastern Pacific, the colder and nutrient-rich bottom water climbs to the surface, so the marine life blooms. Thus, in normal years, without El Ni?o, the surface temperatures are lower in the east than in the west.
So, what event triggers El Ni?o?
For reasons which are not yet clearly known, at intervals of a few years, the tradewinds decrease in intensity or even cease. When these winds weaken, the warm water accumulated off the Indonesian coasts heads eastwards, thus the water temperature off South American coasts rises. This removes the zone of abundant rainfall from western Pacific to east, in central and east Pacific.
But El Ni?o event can affect climate further than the Pacific area, to India and South Africa. At higher altitudes, El Ni?o becomes stronger, and replaces the winds called jet-streams, which moves eastwards at high speeds. The jet streams dictate the movement of the hurricanes.
Increasing or shifting the direction of these currents means harsher or less severe seasonal storms or weather conditions. For example, in the winters with El Ni?o, the weather is milder in northern US, and wetter and colder in southern states.
Currently, El Ni?o forming conditions are monitored in Pacific by balizes measuring water parameters, till 500 m depths. The data are stored in computers that make prognoses.