According to recent reports, India is experiencing a colder winter than usual. While the cold chills our spines, we may forget to question the reasons behind this polar Pacific phenomenon.
We have the answer right here! This cold is caused by the north-south winter current formed by the weather phenomenon known as La Niña.
Normally, El Nino and La Nina occur every 4-5 years. El Nino occurs more often than La Nina. Typically, episodes last nine to twelve months.
And this year La Niña is underway for a record-breaking third year in a row!
Forecasts for 2023 predict that this fall and winter its companion phenomenon, known as El Niño, will occur with more than 50% probability.
Let’s learn the difference between El Niño and La Niña.
Overview of El Niño and La Niña
- While El Niño refers to a band of warmer water stretching from west to east in the equatorial Pacific, La Niña occurs when a band of water spreads from east to west and is cooler.
- Both of these phenomena affect weather worldwide. In addition to its strong impacts on weather, it can also cause changes in the rain-dependent economy.
- The El Niño Southern Oscillation is when El Niño and La Niña together form a cyclical process.
- An El Niño year creates a small-scale global warming crisis because warm water spreads across the tropical Pacific releasing large amounts of heat into the atmosphere.
- It’s possible that this year’s El Niña could increase the planet’s average surface temperature by more than 1.5°C above pre-industrial levels.
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El Niño and La Niña: Impact on the northern Indian Ocean
- According to reports, El Niño summers historically tend to produce the largest deficits in the monsoon, which would occur after the transition from La Niña winters.
- This means that the pre-monsoon and monsoon circulations tend to be weaker during El Niño years.
- The change in wind intensity from the surface to the upper atmosphere is also expected to be weaker and could cause the formation of enhanced cyclones or tornadoes.
- According to reports, India is likely to experience a monsoon deficit in 2023 in case El Niño conditions occur in the summer.
- Extremely wet and dry events are predicted during this monsoon deficit. Isolated areas of heavy or very heavy rainfall are likely, while in other areas seasonal rainfall totals may fall short.
El Niño
source: Wikipedia
- The term El Nino means ‘the boy’ or ‘the Christ child’ in Spanish.
- It was first recorded by South American fishermen in the early 17th century, hence the name of the phenomenon.
- Another reason it has this name is that the warm waters of the Pacific Ocean tend to appear in December.
- El Niño’s large-scale climate-ocean-atmosphere interactions are associated with periodic warming in sea surface temperatures over the central and east-central equatorial Pacific.
- It is associated with high pressure in the western Pacific Ocean.
El Nino: Impact on India
El Nino adversely affects the Indian monsoon and affects agriculture in India.
- When there is no El Nino and it is a normal monsoon year, the pressure distribution causes the Peruvian coast in South America to have higher pressure than areas near northern Australia and Southeast Asia.
- Although the Indian Ocean is warmer than the adjacent oceans, it has relatively lower pressure.
- As a result, winds carrying moisture move from the near western Pacific Ocean to the Indian Ocean.
- Winds carrying moisture move farther from the ocean to land because the pressure on the Indian continent is lower than on the Indian Ocean.
- If this normal pressure distribution is affected for any reason, the monsoon is also affected.
Impact of El Nino?
- El Nino causes cool surface waters off the coast of Peru to warm.
- The normal trade winds are lost or reverse direction when the water warms.
- Moisture-bearing winds move toward the Peruvian coast from the western Pacific, near northern Australia and Southeast Asia, causing heavy rains in Peru during El Niño years and the Indian subcontinent has no monsoon rains. normally.
- The greater the temperature and pressure difference, the greater the rainfall deficit in India.
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La Nina
Source: Wikipedia
- The term La Nina means ‘little girl’ in Spanish. It is also known as El Viejo which means the cold event.
- Unlike normal monsoons, water temperatures in the Eastern Pacific become colder when La Nina occurs.
- There is a strong high pressure in the eastern equatorial Pacific Ocean as a result of this phenomenon.
- Currently, there is low pressure in the Western Pacific and off the coast of Asia.
- Droughts in Peru and Ecuador, massive floods in Australia, high temperatures in the Western Pacific and Indian Oceans off the coast of Somalia and monsoon rains in India are caused by La Nina.
- La Nina is beneficial for the Indian monsoon.
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El Nino and La Nina effects in India
This is because in general, El Nino means less than average rainfall in India, so of the 13 droughts India faced, 10 occurred during El Nino years and one has occurred in La Niña years since 1950.
Indian agriculture is highly dependent on the monsoon and hence, less rainfall during the monsoons often results in below-average crop yields.
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Source: pagasa.edu.vn