India could experience an extended monsoon season this year

THERE IS over 50 per cent chance of a La Niña condition in the equatorial Pacific Ocean during the autumn of 2020, suggests the latest update by the United States National Oceanic and Atmospheric Administration. It adds that once formed, the La Niña condition might continue into the winter season.

Currently, El Niño Southern Oscillation (ENSO), an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, is in neutral condition. The warming phase of ENSO cycle is known as El Niño and its cooling phase as La Niña. It is characterised by the unusual cooling of the central and east-central equatorial Pacific Ocean.

During the past four weeks, equatorial sea surface temperatures were below average from the International Date Line to the eastern Pacific and were above average in the western Pacific. The International Date Line is an imaginary line on the Earth's surface, defining the boundary between one day and the next.

Both El Niño and La Niña are deviations from normal surface temperatures that occur due to the anomalous behaviour of trade winds. In the case of El Niño, the trade winds weaken, leading to warming.

In La Niña, the opposite happens and the trade winds strengthen, leading to cooling. Both these events can have large-scale impacts not only on ocean processes, but also on global weather and climate.

During El Niño, the central and equatorial Pacific Ocean becomes unusually warm. This disrupts global wind patterns, affecting climatic conditions in tropical areas like Africa, sub-tropical areas like India and extra-tropical areas like North America.

El Niño and La Niña episodes typically last nine to 12 months, but some may last for years. While their frequency can be quite irregular, on an average El Niño and La Niña occur every two to seven years. Typically, El Niño occurs more frequently than La Niña.