La Nina has arrived: Know its effects and possibility of weakening

Why in the NEWS?

• The US-based National Oceanic and Atmospheric Administration (NOAA) announced on January 9, 2025 that La Nina conditions are now active in the Pacific Ocean.

Key Points:

• NOAA said that in December 2024, sea surface temperatures in the central and eastern Pacific Ocean were below average, leading to La Nina conditions.
• This condition can have an impact on weather patterns around the world, such as changes in weather conditions in South America, North America, Asia, and Australia.
• NOAA also pointed out that this event will not be as strong and impressive as it may be in other years, as its strength is likely to be weaker.

El Niño and La Niña

• Both La Nina and El Nino are climate phenomena that occur in the equatorial (tropical) Pacific Ocean that have significant effects on global weather patterns. 
• Both of these events cause changes in temperature at the ocean's surface, which affects atmospheric conditions and weather patterns.

El Niño

• El Niño means little boy in Spanish.
• South American fishermen first noticed a period of abnormally warm water in the Pacific Ocean in the 1600s.
• They gave it the full name El Niño de Navidad, because El Niño usually peaks around December.
• El Niño is a natural phenomenon in which sea surface temperatures in the western part of the Pacific Ocean rise above average.
• It is mainly caused by the weakening of the western atmospheric pressure, which usually pulls more warm water eastward into the coastal zone near Asia and Australia.
• During El Niño, water in the western Pacific Ocean warms up, and colder water rises in the eastern Pacific Ocean.
• Effects of El Niño:
  • More rainfall and flooding in South and Central America.
  • Drought and less rainfall in Australia, Southeast Asia, and India.
  • Heat and storms in parts of North America.

Impact of El Nino on India

• Both El Nino and La Nina have profound effects on India's weather and climate.

Effects of El Nino:

• Less rainfall:
  • During El Nino, India experiences weaker monsoon rainfall, which can lead to droughts and water crises. 
  • This is particularly felt in the western and southern parts of India.
• More heat:
  • Due to El Nino, India experiences more heat and heat waves than normal, which has a negative impact on agriculture, health and climate.

La Niña

• La Niña means little girl in Spanish.
• La Niña is also sometimes called El Viejo, the anti-El Niño, or simply "a cold event."
• La Niña has the opposite effect of El Niño.
• During La Niña events, the trade winds are even stronger than normal, pushing more warm water toward Asia.
• Off the west coast of the US, upwelling increases, bringing cold, nutrient-rich water to the surface.
• These cold waters in the Pacific push the jet stream northward.
• Effects of La Niña:
  • More rainfall and flooding in Southeast Asia and Australia.
  • Drought and heat on the western coasts of South America.
  • More chances of cold and storms in parts of North America.

• Both of these phenomena are caused by complex interactions between ocean and atmospheric systems, which are characterized through the Intertropical Convergence Zone (ITCZ) and other ocean-atmospheric patterns.
• The impacts of these events can have profound effects on weather, climate, agriculture, and water supplies around the world.

Effects of La Nina on India

• Increased monsoon:
  • During La Nina, India experiences more monsoon rainfall than normal, which increases the amount of rainfall, especially in northwest India and Bangladesh.
  • This leads to more rain, which can lead to floods and waterlogging.
• Extremely reduced winters:
  • During La Nina conditions, North India experiences cold and extremely reduced winters. 
  • Winter temperatures may be lower than normal, leading to cooling conditions in North India.
• Northeast Monsoon:
  • La Nina boosts rainfall during the northeast monsoon from October to December, leading to more rainfall in eastern and southern India. 
  • This is particularly felt in states like Tamil Nadu, Andhra Pradesh, and Karnataka.

Intertropical Convergence Zone (ITCZ)

• The ITCZ ​​is the region where warm winds from the northern and southern hemispheres meet and rise near the equator. It is also called the tropical convergence zone.
• The ITCZ ​​is located in the Earth's tropical region (between 23.5° north and south latitudes) and it shifts slightly around the equator from time to time.
• This region is the meeting point of two major air currents (tropical winds from the north and south).
• The air that meets here is warm and full of moisture, which rises upward. This leads to the formation of clouds and precipitation.
• The high moisture and heat in the ITCZ ​​causes heavy rainfall, which is prominent in tropical regions such as Africa, Southeast Asia and South America.
• The ITCZ ​​causes monsoons and other rainfall patterns in global weather. When the ITCZ ​​shifts north or south, rainfall activity is affected.
• The ITCZ's usual position is near the equator in spring and autumn, but it can shift northward in summer and southward in winter.
• The activity of the ITCZ ​​also plays a role in the genesis of tropical storms (such as cyclones and hurricanes), as warm and moist air combines here to give rise to stormy events.
• The effects of the ITCZ ​​lead to changes in global climate and weather, such as cold, heat, rainfall, drought and storms.
• The ITCZ ​​is extremely important to tropical rainforests and agriculture as it is a major source of rainfall.

Effects of ITCZ ​​on global weather:

• Rainfall: 
  • The rising air in the ITCZ ​​leads to heavy rainfall and storms wherever it meets with air pressure. 
  • This is why tropical rain forests are found in the region of the ITCZ. For example, the rain forests of Africa, Southeast Asia, and tropical South America receive heavy rainfall.
• Pressure and Monsoon: 
  • There is high pressure in the region of the ITCZ, which causes monsoons and other atmospheric activities in the surrounding areas. 
  • For example, the monsoon in India is influenced by the ITCZ, when the area of ​​the ITCZ ​​moves northward, rainfall begins in India.
• Tropical Storms: 
  • The shifting of the ITCZ ​​also plays an important role in the origin of tropical storms and cyclones. 
  • When warm and moist air organizes in the ITCZ, it can produce phenomena like storms and cyclones.