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El Niño – when the Pacific pauses for breath

08 Dec 2015

Every few years a phenomenon takes place in the Pacific which has far-reaching climate implications across various countries. The effect of this event is termed El Niño which means ‘the little boy’ and refers to the Christ child because it was usually detected just before Christmas by South American fishermen off the coast of Peru.

So what causes El Niño and La Niña?


What the fishermen noticed on a variable but cyclic basis, was that the surface of the normally cold eastern Pacific waters would become warmer. This warmer surface water would widely influence atmospheric circulation, therefore affecting rainfall and temperatures in various parts of the world. Different areas would experience greater or lesser rainfall and higher or lower temperatures than usual. These effects would last a few months to a year or so and then gradually return to more familiar conditions.

However, it is never easy to predict how El Niño will affect a particular region on any regular basis because the effects seem to shift around – occasionally missing out some areas all together and at other times causing unseasonable temperature fluctuations, floods or droughts in those very same places. Because of this, it is sometimes difficult to predict severity or where that severity will bite the hardest. And unfortunately, by the time El Niño’s pattern emerges, it may be too late for farmers to do much about it. Although there are often several years between each El Niño event – sometimes followed by its little sister, La Niña – each episode can play havoc with crop production.    

So what causes El Niño and La Niña?

What we do know about this occurrence is how it happens. What we don’t fully understand, is why. The Pacific is the largest body of water on the Earth and covers nearly half the planet. So when any anomalies take place across this vast area, it is naturally going to affect weather patterns in many areas across the globe. Any changes in the ocean will impact the atmosphere and therefore affect climate patterns. In turn, changes in the atmosphere impact the ocean temperatures and currents. However, possibly the biggest single culprit may be the sun which affects atmospheric pressure around the globe.

El Niño

El Niño comes about through a shift of influence between a low pressure area in the west of the equatorial Pacific and a high pressure area in the eastern Pacific. Under normal conditions air flows from the high pressure area to the low area, creating the strong westerly trade winds that draw the warm surface water away to the west, thus cooling the ocean along the Pacific South American coast.

However, this pressure gradient sometimes lessens as the pressure areas undulate slightly. With a lesser gradient, the wind weakens and no longer cools the ocean, thus allowing the sea surface temperature (SST) in the eastern Pacific to become warmer. This causes changes in the atmospheric conditions which move around creating a kind of domino weather effect across various countries. When SST anomalies are greater than 5C degrees, then we know El Niño is on its way.

La Niña

However, like two balancing balls on a see-saw, the pressure areas may not only revert to their usual condition but actually swing to the opposite, creating counter consequences to the outcomes of El Niño. When this happens the sea temperature cools even more than normal, thus creating a very cold sea surface temperature, which in turn has a range of effects rather like El Niño but in different places. For instance, parts of Australia and Indonesia are prone to drought during El Niño, but are typically wetter than normal during La Niña.

Some cool/warm facts about the Nins 

  • Both terms refer to large-scale changes in sea-surface temperature (SST) across the central and eastern tropical Pacific
  • El Niño and La Niña are extreme phases of a naturally occurring climate cycle referred to as the El Niño Southern Oscillation (ENSO)
  • SSTs are used to measure the state of the ocean and El Niño can be forecast up to 9 months ahead with good skill
  • An El Niño/La Niña forecast is NOT a rainfall forecast
  • The Southern Oscillation has been noticed and noted since early 1900’s but official recordings only began in 1950  
  • Fourteen El Niño’s have been recorded between 1950 and 2003  
  • The strongest El Nino ever recorded was the 1997 – 1998 cycle which had no particular affect on South Africa   
  • The El Niño of 1983 however, created the worst drought in Southern Africa for many years  
  • El Niño develops every 2 – 7 years and lasts approximately a year  
  • La Niña can last 1 – 3 years  
  • The upwelling of cold water under La Niña brings nutrient rich waters to the surface, and fishing is good during this time.

The strongest El Niño ever recorded was the 1997 – 1998 cycle which had no particular affect on South Africa

The drought this year affecting west coast farmers

This year’s El Niño has been described as a little more erratic than usual. It is also predicted to be the worst on record but that remains to be seen. Although the southern part of Africa generally receives below-normal rainfall during El Niño years and La Niña usually brings normal or above-normal rainfall, it cannot be accepted as a rule. Southern Africa can be divided into numerous rainfall regions, each region having a different correlation with ENSO. This year South Africa’s west coast farmers have been particularly affected by El Nino.

At Netafim we have developed a range of innovative irrigation solutions to precisely combat the ravages that drought can inflict – systems that can in fact make the desert bloom! And we are evolving all the time. We believe that farmers should take advantage in the good years to prepare for the bad. Investigate all possibilities of surviving the worst nature can throw at you. Bring us your challenges and let’s work together to develop the designs and technology that could very well take the sting out of the next smack of El Niño.  

At Netafim we have developed a range of innovative irrigation solutions to precisely combat the ravages that drought can inflict


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