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Editorial Notes

Forecast of IMD and Disaster Management [With special coverage on El Niño & La Niña]

The forecast from the India Meteorological Department of above-normal temperatures over much of India in the summer months is bound to bring back memories of last year’s withering weeks. If this year’s forecast comes true, though, there is no escape route.
By IT's Editorial Board
March 02, 2017

 

GS (M) Paper-3: “Disaster and disaster management.”
GS (M) Paper-1: “Important Geophysical phenomena”

 

Forecast of IMD and Disaster Management [With special coverage on El Niño & La Niña]

Introduction:

  • It is important to note that Global weather in recent times has come under pressure from the El Nino warming that began in 2015 and exerted its influence into the first quarter of 2016.
  • Further, it is also significant to note that the Australian international weather bureau says there is a 50% prospect of a similar phenomenon this year as well, making it a significant alert on hotter temperatures, and possibly a debilitated monsoon and weaker agricultural prospects.

Impact:

ias-toppers-featured-El-Niño

  • As the temperature edged past 40ºC last year, schools in some states decided to extend their summer vacations by a week or two.
  • This may become necessary again.
  • Urban water distress poses another challenge, because big cities in several States have not received adequate rainfall to replenish their reservoirs and are using up groundwater at unsustainable rates.
  • For farmers, another harsh period would add to their difficulties, requiring a sensitive approach to their needs.
  • Administrative decisions for summer management will need to be refined on the basis of coming IMD updates, although the overall trend appears to be clear.

Conclusion:

  • Temperatures in different parts of the world may have variations due to local weather phenomena.
  • The effect of El Nino on the global temperature average is only a small part of the overall rise, indicating that the trend could be correlated with the rise in greenhouse gases.
  • There are clear signs that the world must shift away from further high-emission pathways in the economy and adopt leapfrogging technologies.
  • It is also a call for policy initiatives to build resilience by improving water harvesting and expanding tree cover, including in cities.
  • For rural India, building surface irrigation facilities such as ponds through the employment guarantee scheme and climate funds would seem a natural choice, while urban water supply augmentation needs more reservoirs to be built.

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:

ias toppers El Niño and La Niña

  • 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.
  • 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:

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  • 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:

ias toppers GRAPHIC-El-Nino

  • 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.

ias-toppers-El-Niño-effects

  • 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.

iastoppers Economic Effects of El Niño

  • 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.

ias toppers Economic Effects of El Niño

  • 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.
[Ref: The Hindu, NOAA]

 

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