la-nina-weather-phenomenon-is-back

Context: According to the World Meteorological Organization, the La Niña phenomenon is back in the central and eastern equatorial Pacific Ocean after nearly a decade’s absence.

More on the news:

  • The La Niña of 2020 is expected to be moderate to strong. The last time there was a strong La Niña event, was in 2010-2011, followed by a moderate event in 2011-2012.
  • There is a high possibility (90 percent) of tropical Pacific sea surface temperatures remaining at La Niña levels through the end of 2020 and maybe through the first quarter of 2021 (55 percent).

Probable Implications

  • Worldwide scenario
    • The weather phenomenon could last into 2021, affecting temperatures, precipitation, and storm patterns in many parts of the world.
    • The phenomenon will result in sea surface temperatures between two and three degrees Celsius cooler than average.
      • However, 2020 is on track to be one of the warmest years on record and 2016-2020 is expected to be the warmest five-year period on record.
  • Asia: 
    • The Horn of Africa and Central Asia will see below-average rainfall due to La Niña.
    • East Africa is forecast to see drier-than-usual conditions, which together with the existing impacts of the desert locust invasion, may add to regional food insecurity.
    • La Niña could also lead to increased rainfall in southern Africa
    • It could also affect the southwest Indian Ocean Tropical Cyclone season, reducing the intensity. 
    • Southeast Asia, some Pacific Islands, and the northern region of South America are expected to receive above-average rainfall.
  • India: In India, La Niña means the country will receive more rainfall than normal, leading to floods.

La Niña weather phenomenon

  • It means the large-scale cooling of ocean surface temperatures in the central and eastern equatorial Pacific Ocean, together with changes in the tropical atmospheric circulation, namely winds, pressure and rainfall.
 

El Nino and La Nina:

  • El Nino and La Nina are opposite phases of what is known as the El Nino-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.
  • La Nina 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 and Indian monsoon.

 

About the World Meteorological Organisation (WMO)

  • WMO was created in 1950 as an intergovernmental organization.  
  • It became a specialized agency of the United Nations, in 1951, for meteorology (weather and climate), operational hydrology and related geophysical sciences.  
  • WMO is the UN systems authoritative voice on weather, climate and water.  
  • Secretariat - Geneva, Switzerland.  
  • Through its members, WMO provides forecasts and early warnings to nations, which help prevent and mitigate disasters.  

Objectives: 

  • WMO monitors and forecasts the transport of chemical and oil spills, forest fires, volcanic ash, haze and nuclear isotopes.  
  • It also draws world attention to the depletion of the ozone layer.  

Source: DTE