Reporting — 20 May 2016

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by Alana Gale

photo “Drought” by Javier Carabelli

 19 May 2016. Santiago, Chile. For the Chilean people, El Niño is more than just a familiar concept. It’s occurring right now, and it actually has a big impact on the country’s weather cycle.

 What is El Niño?

El Niño itself is the name for one phase of the El Niño-Southern Oscillation cycle (ENSO). The cycle refers to fluctuations in the temperatures of the Pacific Ocean, right along the equator.

El Niño is the warm phase. During this phase, water temperatures in the Pacific Ocean are unusually high, as much as 7 degrees Fahrenheit above average. The cold phase is called La Niña. So the water temperatures during La Niña are lower than normal. El Niño happens more often than La Niña.

Normally, each phase lasts nine to twelve months. On average, they are only supposed to occur every two to seven years.

But recently, these weather phenomena, particularly El Niño, have been especially strong. CNN reported that the El Niño weather event in 2015 was one of the three strongest ever recorded. This is very important for Chile, because El Niño can largely impact the weather in South America.

 El Niño’s Connection with the Weather in Chile

One effect for Chile of El Niño is a raise in temperatures, said climatologist Roberto Rondanelli to Bio Bio Chile. Rondanelli is an investigator at the Weather and Climate Resilience Center. Back in September 2015, he predicted that those last months of 2015 would be hotter than usual because of El Niño, especially in the central zone of Chile. And later reports confirmed it, with 2015 the hottest year on record since 1880.

El Niño can also cause another major change in weather patterns: increased precipitation. From Region III to Region VII of Chile, there can be a greater total amount of rainfall, or more intense rain. But why?

The atmospheric circulation in Chile, which is what influences the weather patterns of the country, is defined by two factors.

The first is called the South Pacific subtropical anticyclone. This is a circulation of winds in a region of high atmospheric pressure. It contributes to the usual weather in the north and center of Chile.

The second is the Subpolar Low-Pressure Belt, a region of very low pressure normally situated between 45° and 55° South latitude. The belt moves to lower latitudes during the winter, causing the development of frontal weather systems between La Serena and Concepción in Chile.

With El Niño around, the South Pacific subtropical anticyclone weakens, which decreases its effects on the central and northern parts of the country. This means that frontal systems coming from the west can move more easily to these places. So these areas have more frontal cloud bands, which in turn generate a greater amount of rainfall.

This rainfall is often a welcome sight for many areas of central Chile, where there are frequent droughts.

This does not include the northern desert. It hardly rains at all in Atacama, the world’s driest desert.  The average rainfall in Iquique, for example, is almost zero, 0.03 inches.

Yet the bottom of the desert gets rain, at least on rare occasions.  Last year there were devastating floods.  Some of the children living in that region had never seen rain.  We wrote about that here.

It is this region from the bottom of the Atacama Desert south toward Santiago where there is some agriculture, at least wine and table grapes along the river valleys, where rain and moreover mountain snow is needed and is expected, at least a little to keep farming going.

Unfortunately, what follows El Niño could actually make things worse for that area and central Chile. In the area around Santiago, rainfall is just above the definition of a desert.  In other words, it rains in central Chile about the same as Los Angeles, California.

The Aftermath of El Niño

Climate experts, who met at the International Meteorological and Oceanographic Conference of the Southern Hemisphere in October, discussed what would happen after El Niño.

The experts thought it was likely that La Niña would follow. And just four days ago, the US National Oceanic and Atmospheric Administration published an article saying that there were signs La Niña might develop.

Because La Niña is the opposite phase of El Niño, the weather during La Niña is usually opposite, too. It is typically cooler and drier in Chile during La Niña.

If La Niña returned, the droughts already taking place in dry zones of Chile would probably continue, or even intensify, say the climate experts.

So El Niño and El Niña play a big part in the weather in Chile.

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