Understanding El Nino & La Nina

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Dave_Here
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Sun Dec 02, 2018 8:37 pm

Here we'll collect some articles in English mostly, please volunteer and translate to English if the articles are not in Hindi (you don't have to translate everything, just the important points) :) read more here:
https://www.drishtiias.com/hindi/intera ... ?f=12&t=94

Thanks..
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Dave_Here
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Sun Dec 02, 2018 8:42 pm

:arrow: https://oceanservice.noaa.gov/facts/ninonina.html



  • El Niño and La Niña are opposite phases of what is known as the El Niño-Southern Oscillation (ENSO) cycle. The ENSO cycle is a scientific term that describes the fluctuations in temperature between the ocean and atmosphere in the east-central Equatorial Pacific (approximately between the International Date Line and 120 degrees West).
  • La Niña is sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO. These deviations from normal surface temperatures can have large-scale impacts not only on ocean processes, but also on global weather and climate.
  • El Niño and La Niña episodes typically last nine to 12 months, but some prolonged events may last for years. While their frequency can be quite irregular, El Niño and La Niña events occur on average every two to seven years. Typically, El Niño occurs more frequently than La Niña.
For more points pls click on the link. You may also post important information here.. :geek:
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Dave_Here
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:arrow: https://www.environmentalscience.org/el ... nvironment
  • We know that there are many anthropogenic forcings on the climate, particularly the volume of carbon and greenhouse gases pumped into the atmosphere as a part of our everyday lives. Yet there are a number of natural processes that affect local weather, regional climate and global conditions. Some effects on our climate are a result of fluctuations and anomalies in the complex water conveyor belts of the ocean currents of the world. These fluctuations are known as “oscillations” and the two best-known oscillations are El Niño and La Niña.
  • Oscillations occur naturally in oceans all across the world; some have a limited impact on the regional weather and wider climate, and some have a much greater impact (4). El Niño and La Niña are examples of oscillations that have a greater impact on our climate with effects that are perhaps surprisingly felt all over the globe (5). In economies that are dependent on certain weather conditions occurring regularly and on time (annual summer rainfall, spring ice melt etc), erratic oscillations can cause problems in these areas leading to drought. Knock on effects can lead to fish migrations and economic hardship for areas that rely on fish stocks. Marginal areas suffer or thrive depending on the effects of El Niño and La Niña leading to further knock on effects elsewhere (4).
  • Both El Niño and La Niña are opposite effects of the same phenomenon: the ENSO (El Niño Southern Oscillation). Both are an oscillation in the temperatures between the atmosphere and the ocean of the eastern equatorial Pacific region, roughly between the International Dateline and 120 degrees west (2). El Niño - the conditions for which build up between June and December (15) - is caused by a change in the wind patterns (5). Here, the Pacific Trade Winds fail to replenish following the summer monsoons of Asia (7). This warmer air leads to an oscillation between the cooler and warmer waters, leading to warmer ocean temperatures than normal.
  • Peruvian fishermen roughly around the start of the 20th century who first noticed the correlation between temperature changes and anchovy stocks that led to the development of study in this area (4), though they had noticed variations in fish stock for centuries. Every three to seven years and between December and January, there is a massive tailing off of stocks of the fish that the local economy relies on (7). Why does this happen? Up-swellings from the sea bed occur in normal years that bring nutrients up to the plankton to feed on and in turn abundance of plankton is beneficial to marine life up the food chain. In an El Niño year, that swelling does not occur so the plankton is reduced and in turn, so are the fish stocks, mostly through failure to reproduce (8).
  • La Niña is effectively the opposite of El Niño, indicated by prolonged periods of sea temperatures in the same region (2), and the effects stated above are generally reversed. During non El Niño years, atmospheric pressure is lower than normal over the western Pacific area and higher over the colder waters of the western Pacific, as already discussed. With La Niña, the Trade Winds are particularly strong in carrying warmer water westwards across the Pacific leading to colder than average temperatures in the east and warmer than average temperatures in the west (9). The result is that plankton increases in the areas where the temperature is cooler, leading to a positive effect on the marine life that depends on plankton or depends on those creatures that depend on plankton (11).
There's more in the article about Climate Change...
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Dave_Here
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Sun Dec 02, 2018 9:26 pm

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