La Nina

Syllabus: General Studies Paper 1

An uncommon phenomenon, La Ninã conditions prevailing over the equatorial Pacific Ocean since September 2020 has entered the third year. There are only six instances of La Ninã lasting for more than two years since 1950s , data with the India Meteorological Department (IMD) show.

• La Nina is when the sea surface temperatures (SSTs) along the central and equatorial Pacific Ocean are colder than normal, which, favour the Indian summer monsoon. 
• However, La Nina years are also infamous for frequent and intense hurricanes and cyclones in the Atlantic Ocean and the Bay of Bengal.

Impacts of La Nina

• La Nina tends to lead to milder winters in Northern Europe and colder winters in southern/western Europe leading to snow in the Mediterranean region.
• It is continental North America where most of these conditions are felt.
• La Nina causes drought in the South American countries of Peru and Ecuador.
• It usually has a positive impact on the fishing industry of western South America.
• In the western Pacific, La Nina increases the potential for landfall in those areas most vulnerable to their effects, and especially into continental Asia and China.
• It also leads to heavy floods in Australia and high temperatures in Western Pacific, Indian Ocean, off the Somalian coast and a comparatively better monsoon rains in India.

El Nino

• The phrase “El Niño” refers to the Christ Child and was coined by fishermen along the coasts of Ecuador and Peru to describe the warming of the central and eastern pacific
• In a normal year, a surface low pressure develops in the region of northern Australia and Indonesia and a high-pressure system over the coast of Peru. As a result, the trade winds over the Pacific Ocean move strongly from east to west.
• The easterly flow of the trade winds carries warm surface waters westward, bringing convective storms (thunderstorms) to Indonesia and coastal Australia. Along the coast of Peru, cold bottom cold nutrient rich water wells up to the surface to replace the warm water that is pulled to the west.

El Nino impacts monsoon rainfall in across the globe

• El Nino impacts ocean temperatures, the speed and strength of ocean currents, the health of coastal fisheries, and local weather from Australia to South America and beyond.
• Rainfall increases drastically in South America, contributing to coastal flooding and erosion.

El Nino impacts monsoon rainfall in India

• El Nino and Indian monsoons are inversely related.
• The most prominent droughts in India – six of them – since 1871 have been El Nino droughts, including the recent ones in 2002 and 2009
• However, not all El Nino years led to a drought in India. For instance, 1997/98 was a strong El Nino year but there was no drought.
• On the other hand, a moderate El Nino in 2002 resulted in one of the worst droughts.
• El Nino directly impacts India’s agrarian economy as it tends to lower the production of summer crops such as rice, sugarcane, cotton, and oilseeds.