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Source: The post on Why Global Models Got La Niña Predictions Wrong and Its Impact is based on the article “Why global models went wrong with their La Niña predictions — and what its delay means” published in Indian express on 7th September 24.
What is the News?
Nearly all major global weather agencies had forecasted the onset of La Niña by July 2024. However, the delay in its arrival has rendered the prediction inaccurate.
About El Nino and La Nina
| Aspects | Description |
| About | 1. ENSO is marked by fluctuations in sea surface temperatures in the tropical Pacific Ocean, driven by atmospheric variations. 2. These fluctuations affect global atmospheric circulation and influence weather patterns globally. 3. ENSO has three phases: El Niño (Warm phase), La Niña (Cool phase), Neutral phase. 4. ENSO cycles occur irregularly every two to seven years. 5. Anthropogenic climate change has intensified the effects of both El Niño and La Niña, exacerbating hazards such as high temperatures, heavy rainfall, and droughts |
| Mechanism | 1. During El Nino, trade winds weaken, reducing the movement of warm waters to the west. This results in the eastern Pacific becoming warmer than usual. 2. In La Nina, trade winds strengthen, pushing more warm water toward the western Pacific, making the eastern Pacific cooler than usual. 3. During the neutral phase, the eastern Pacific (near the northwestern coast of South America) is cooler than the western Pacific (near the Philippines and Indonesia) due to prevailing east-to-west trade winds. 4. These trade winds move warm surface water westward, and cooler water from below rises to the surface in the east to replace it. |
| Impact on Indian Monsoon | El Nino is associated with suppressed monsoon rainfall in India. La Niña supports enhanced monsoon activity. |
Reasons for Prediction Errors:
1. Weak La Niña phases are more difficult for weather models to detect than stronger events.
2. Other atmospheric factors, such as inter-seasonal variability and the Madden Julian Oscillation (MJO), added complexity and made predictions harder.
Current Situation: As of September, ENSO-neutral conditions prevail, and La Niña is expected to emerge by late September or early October. La Niña is predicted to peak in November 2024 and last through the winter in the northern hemisphere.
Impact of La Niña Delay on India’s Monsoon
1. La Niña typically enhances the southwest monsoon in India (June to September), but the delay means it won’t directly influence this season’s rainfall.
2. Other factors also contribute to a robust monsoon, with India recording 16% surplus rainfall in August and the IMD forecasting 109% above-normal rainfall in September.
3. India has received 8% more rainfall than usual for the season, though regional variations persist, with deficient rainfall in the east and northeast, and surplus rainfall in central and southern India.
4. La Niña’s influence could extend to the northeast monsoon (October-December), but it generally doesn’t favor enhanced rainfall during this period.
5. Regions like Tamil Nadu, coastal Andhra Pradesh, and Kerala may experience normal or lower rainfall, though there have been exceptions in the past.
UPSC Syllabus: World Geography
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