What is El Niño?

El Niño is the warm phase of the El Niño-Southern Oscillation cycle (ENSO). The ENSO cycle is the way scientists describe the fluctuations in temperature between the atmosphere and the ocean in the east-central Equatorial Pacific. Basically, El Niño is a naturally occurring phenomenon that is linked to a periodic warming in sea surface temperatures across the central and east-central Equatorial Pacific. El Niño is Spanish for “the boy child,” which is often used to refer to Jesus Christ, and the phenomenon earned this name because it typically occurs in December around Christmas. El Niño occurs every 2-7 years, and can last anywhere between nine months and two years.

El Niño and La Niña are opposite phases of El Niño-Southern Oscillation (ENSO) cycle. While El Niño as the warm phase of ENSO, La Niña is sometimes referred to as the cold phase of ENSO.

According to Wikipedia,

El Niño is the warm phase of the El Niño Southern Oscillation (commonly called ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (between approximately the International Date Line and 120°W), including off the Pacific coast of South America.

The cool phase of ENSO is called “La Niña” with SST in the eastern Pacific below average and air pressures high in the eastern and low in western Pacific. The ENSO cycle, both El Niño and La Niña, causes global changes of both temperatures and rainfall.

el-nino-la-nina

Both El Niño and La Niña typically last nine to 12 months. The frequency of occurring of El Niño is more than La Niña. The presence of El Niño can significantly influence ocean conditions and weather patterns across large portions of the globe.

What Causes El Niño?

The following are the conditions in the equatorial Pacific Ocean prior to the occurrence of El Niño:

  • The tropical pacific has consistent westerly moving trade winds. The trade winds push warm water on the surface of the ocean from east to west (westerly). This causes the warm water to build up on the western side of the ocean near Asia.
  • Meanwhile, on the eastern side of the ocean, near Central and South America, cold waters are pushed up towards the surface. Because of this, there is a difference in temperature across the equatorial pacific, with warm water to the west and cold water to the east.
  • The warm water in the west heats the air, making the warm air rise and leading to drastic weather, including rain and thunderstorms. The rising warm air causes a circulation between east and west in the Pacific, with the warm, moist air rising in the west, and cool, dry air descending in the east.
  • All of these natural occurrences lead to a reinforcement of the easterly winds, and cause a self-perpetuating motion in the air in the Pacific.

This self-perpetuating motion in the air in the Pacific continues until the slow changes in the ocean around the equator lead to a series of events known as El Niño:

  • Under the proper conditions, the trade winds are weakened, causing less warm surface water to be pushed to the west, and less cold water to be pulled to the surface in the east. Parts of the ocean that are cold during the usual self-perpetuating cycle become warmer, cancelling out the normal difference in temperature in the equatorial Pacific between east and west.
  • With the ocean temperature evened out, and the warmest waters being more toward the center of the ocean, the cloudy, rainy weather that typically occurs in the east now occurs in the center of the ocean.
  • Rainfall patterns over the equatorial pacific are changed due to the diminishing of the trade winds and movement of warm water.
  • This movement of the warm waters also causes a change in the wind cycles. The wind is now blowing out from the center of the ocean to the east and to the west.
  • All of this leads to drastic changes in temperature and weather around the world.

What are The Effects of El Niño on the Weather?

The main impacts of El Niño occur in and around the Tropics. The following are some of the effects El Niño has on the weather in this part of the world:

  • In South America, there is a drastic increase in the risk of flooding on the western coast, while there is an increase in the risk of droughts on parts of the eastern coast.
  • In eastern countries, like India and Indonesia, there is an increase in droughts.
  • In general, El Niño causes vast amounts of rainfall in the eastern parts of the Pacific (the western coast of South America), and very dry weather on the western parts (India, Indonesia).
  • With all the extra heat at the surface of the Pacific Ocean, energy is released into the atmosphere, causing an overall warming of the global climate temporarily. Years in which El Niño occurs tend to feature higher temperatures across the globe.
  • The effects of El Niño on the weather peak in December and can last for several months after that.
  • After El Niño, the trade and easterly winds often fall back into their normal, self-perpetuating cycle. However, on some occasions the effect is reversed in a process called La Niña. During La Niña, the trade winds are strengthened, causing the normal cycle to be more dramatic and having the reverse effect of El Niño.

What is La Niña?

La Niña is a strengthening of the normal trade winds that typically occurs after El Niño. Basically, the normal, non-El Niño wind cycle is reinforced, pushing the warmest waters in the equatorial pacific further west than normal, and increasing the pulling up of cold water to the surface in the east. La Niña has an effect on global weather, as well, and this effect is typically the opposite of El Niño, causing droughts in the eastern equatorial Pacific and floods in the western equatorial pacific.

What are the Economic Effects of El Niño?

  • In Asian countries, there is typically a decrease in rice production. With an increase in droughts on the western side of the equatorial Pacific, GDP in the countries in that area tend to drop during the El Niño cycle. For countries in that area that harvest rice, water is needed, and the lack of rain can have a huge impact on their rice production. Because rice production is of great importance in many of these Asian countries, El Niño has a negative impact on these countries’ economies.
  • In non-Asian countries that are impacted by these El Niño related droughts, such as Australia, the droughts can cause a decrease in the harvesting of other crops, like wheat. For farmers and exporters of these crops, El Niño has a very negative economic impact, similar to that of rice production and exportation in the Asian countries.
  • Meanwhile, the dramatic increase in rainfall on the eastern side of the equatorial Pacific drastically increases the chances of flooding in countries in that area. This flooding can cause property damage to the point where people have to leave their homes and seek shelter elsewhere. The flooding can also cause damage to crops, leading to a similar impact economically that occurs with the droughts on the western part of the equatorial Pacific.
  • Fishing in equatorial coastal countries like Ecuador and Peru becomes difficult, as fish in the waters near these countries tend to disappear in the months of December and January.
  • Overall, the drastic change in weather that occurs due to El Niño has a negative economic impact on many countries near the equator. While normal years offer more stable weather, thus leading to more predictable effects on certain markets, El Niño years have a dramatic shift in the weather pattern that leads to extreme weather on either side of the equatorial Pacific. This extreme weather, whether it be drought or flood, has a negative impact on the living conditions and extraction of natural resources in Tropical countries.

El Niño is a naturally occurring event, and there is nothing that can be done to stop its effects on the weather or on people around the world. However, because it can typically be noticed by meteorologists, people in the countries affected by it can take measures in order to curb some of the impact.

Whether it be preparing for floods or droughts, people in the countries affected by El Niño must take the steps necessary to protect themselves. This can include stocking up on water in the case of a drought, or making sure their homes are able to handle flood waters. Because of the effect on many important crops in these countries, some steps for preparation might also include stocking up on these crops in preparation for the droughts or for damage caused by the flooding.

Source: NOAA
Image credit: Fondriest Environmental

Rinkesh

Rinkesh is passionate about clean and green energy. He is running this site since 2009 and writes on various environmental and renewable energy related topics. He lives a green lifestyle and is often looking for ways to improve the environment around him.