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La Nina

Posted on May 10, 2022 by admin1  588

In News

  • The La Nina is being blamed this year for worsening the longest spell of heat waves in north, west and Central India.

About El Niño-Southern Oscillation (ENSO)

  • ENSO is a global phenomenon, which affects the temperature and precipitation of many regions around the globe, including the Indian subcontinent. The most important factor with the ENSO is the ability of the scientists to predict its occurrence, thereby predicting the amount of rainfall and temperature in the region. ENSO includes three phenomena:

El-Nino

  • El-Nino: It leads to warming in surface temperature of the eastern Pacific Ocean region. This is associated with an increase in rainfall along the western coast of South America and a decrease in rainfall over the Indian subcontinent. It also leads to westerly winds, instead of the generally occurring easterly winds. 

 

La-Nina

  • La-Nina: It is the reverse phenomenon of El-Nino. The temperatures over the eastern Pacific Ocean decreases, along with a decrease in rainfall. Also, the rainfall over the Indian subcontinent increases, along with augmentation of the strength of surface-level easterly winds.
  • Neutral: These years are not associated with any of the above phenomena.
  • Southern Oscillation: This is the interconnection which was established between the El-Nino and the decrease in rainfall over the Indian subcontinent. Although the fishermen and later the scientists knew both the phenomena, the two were thought to be independent of each other. It was quite later that interconnection was established between the two and it was named Southern Oscillation.

Impact of ENSO on the Indian Subcontinent

  • Weather: El-Nino causes higher temperatures and lesser rainfall over the Indian subcontinent, during the monsoon season. On the other hand, la-Nina increases the rainfall and decreases the temperature. Therefore, it is the La-Nina which is (ironically!) much warmly welcomed in the Indian subcontinent.
  • Disasters like Drought and Floods: While El-Nino leads to drought events in the subcontinent, La-Nina is primarily associated with flood events. These disasters affect the socio-economic status of the affected communities.
  • Health: El-Nino induced droughts lead to wildfires and forest fires, thus worsening respiratory diseases like asthma. On the other hand, La-Nina leads to flooding, inducing water-borne diseases like Cholera, Malaria, Jaundice etc.
  • Irrigation: The irrigated area accounts for 48.8% of the total agricultural area of the country (almost 140 million ha). The remaining 51.2% is rainfed. This rainfed area is chiefly dependent upon the monsoonal rains. Therefore, the El-Nino induced rainfall-deficit year brings worries for Indian farmers, while La-Nina induced surplus year is widely welcomed by the Indian farmers.
  • Economy: As the monsoon plays an important role in Indian agriculture and the Indian economy and also the fact that India is a primarily agricultural country, ENSO affects the Indian economy in a major way. Better agricultural output means better returns for the Indian farmers and rural population. This induces demand and raises the economic output of the country. Since the ENSO impacts farmers and rural poor more, it also has an important role in the reduction or exacerbation of the inequality of the country.
  • Ecosystem: ENSO causes warmer and colder temperatures in the sea surface waters. Since the corals are a delicate ecosystem, the temperature change has the potential to affect the coral ecosystem. Apart from that, ENSO events lead to wildfires, droughts and floods as stated above, thus impacting the wildlife and biodiversity.

Temperatures defying La Nina

  • Spike in temperature: According to the meteorological department, the temperature is 5 °C greater than the usual temperatures in this season this year. This is in conflict with the usual La-Nina years, which brings cold winds from the pacific and keeps the temperature low. The March of 2021 has been the 3rd warmest in 121 years. The warmest March was in 2010 and the second warmest was in 2004.
  • Greenhouse Effect: Scientists have not discounted the effect of the greenhouse effect on a La-Nina year, which may increase the temperature. However, the fluctuation has caused concerns over the future of ENSO in the Indian subcontinent.

Impacts El Niño  

  • The outcomes of each El Niño event are never exactly the same: they depend on the intensity of the event, the time of year when it develops and the interaction with other climate patterns.
  • El Niño is often associated with warm and dry conditions in southern and eastern inland areas of Australia, as well as Indonesia, the Philippines, Malaysia and central Pacific islands such as Fiji, Tonga and Papua New Guinea. 
  • During the northern hemisphere summer season, the Indian monsoon rainfall generally tends to be less than normal. 
  • In the northern hemisphere winter, drier than normal conditions are typically observed over south-eastern Africa and northern Brazil.
  • Wetter than normal conditions are typically observed along the Gulf Coast of the United States, the west coast of tropical South America (Colombia, Ecuador and Peru) and from southern Brazil to central Argentina. 
  • Parts of eastern Africa (Kenya, Uganda) also usually receive above-normal rainfall. 
  • El Niño is associated with milder winters in north-western Canada and Alaska due to fewer cold air surges from the Arctic – a result of a large-scale region of lower pressure centred on the Gulf of Alaska/North Pacific Ocean.

Source: TH

 
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