Unlocking the Mystery of El Niño and La Niña: How Do They Impact Global Weather Patterns?
The India Meteorological Department (IMD) recently forecasted above-normal rain in the upcoming monsoon season in India, with favorable La Nina conditions expected to set in by August-September. This news has sparked interest and concern among meteorologists and the general public alike, as the onset and withdrawal of conditions related to El Niño or La Nina can have significant impacts on weather patterns across the globe.
El Niño and La Nina are climate phenomena that result from ocean-atmosphere interactions, impacting the temperature of waters in the central and eastern tropical Pacific Ocean. These phenomena have global implications on weather patterns. Under normal ocean conditions, trade winds blow westwards along the equator from South America towards Asia, resulting in upwelling where cold water rises and displaces warm surface waters. However, during El Niño, weak trade winds get pushed back towards South America, leading to warmer-than-usual sea surface temperatures. Conversely, during La Nina, strong trade winds push warm water towards Asia, resulting in colder and nutrient-rich water towards South America.
The El Niño Southern Oscillation (ENSO) cycle includes El Niño, La Nina, and a neutral phase. El Niño events are more frequent than La Nina events, occurring once every two to seven years. La Nina conditions prevailed between 2020 and 2023, and the recent weakening of El Niño conditions is expected to transition to neutral ENSO conditions by June, followed by the emergence of La Nina conditions by August.
The impact of La Nina on global weather patterns is significant. Changes in ocean temperatures affect air circulation loops, influencing precipitation levels in neighboring regions and impacting phenomena like the Indian monsoon. In India, above-normal rainfall is forecasted for the upcoming monsoon season, with the seasonal rainfall expected to be 106 percent of the Long Period Average. While most regions are expected to receive normal or above-seasonal rainfall, east and northeast India may experience below-average rainfall during La Nina years, leading to potential water shortages and increased thunderstorm activity.
Internationally, countries like Indonesia, the Philippines, and Malaysia typically receive good rainfall during La Nina years, while regions in North America and Africa may experience droughts or below-average rainfall. La Nina also affects hurricane activity over the Atlantic Ocean, with increased hurricane activity during La Nina years.
Climate change is also impacting the ENSO cycle, with studies suggesting that global warming may trigger more El Niño events. The World Meteorological Organization has warned that climate change is likely to intensify extreme weather events associated with El Niño and La Nina.
In conclusion, the onset of La Nina conditions in India and globally is expected to have far-reaching implications on weather patterns, precipitation levels, and extreme weather events. Understanding and monitoring these climate phenomena is crucial for preparedness and adaptation to the changing climate dynamics.