El Nino, La Nina, and India's changing monsoon

It’s already mid-June, and the much-awaited monsoon showers are nowhere in sight. And as the rains play truant, once again El Nino – a phenomenon which is experiened the world over – is to blame.

El Nino and La Nina are opposite phases of the El Nino–Southern Oscillation (ENSO), a recurring climate pattern in the tropical Pacific Ocean. They strongly influence India's southwest monsoon, which provides about 70–80% of the country's annual rainfall.

El Nino is characterized by unusually warm waters in the central and eastern Pacific Ocean.

EL NINO’S EFFECTS ON INDIA

• Monsoon rainfall tends to be below normal


• Increased likelihood of droughts and water shortages


• Higher summer temperatures


• Reduced agricultural productivity if rainfall deficits are significant


• More frequent dry spells during the monsoon season

MECHANISM
El Nino weakens the large-scale atmospheric circulation that helps draw moisture-laden winds toward India, reducing monsoon strength.

SOME EL NINO YEARS
Several major drought years in India, such as 1982, 1987, 2002, and 2015, were associated with El Nino conditions.

LA NINA AND THE INDIAN MONSOON
La Nina is characterized by unusually cool waters in the central and eastern Pacific Ocean.

LA NINA’S EFFECTS ON INDIA

• Monsoon rainfall is often above normal


• Stronger monsoon winds and moisture transport


• Increased chances of floods and heavy rainfall events


• Better water availability and generally favourable conditions for agriculture

MECHANISM
La Nina strengthens atmospheric circulation patterns that support the Indian monsoon, enhancing rainfall over much of the country.

EXAMPLES
Years such as 2010, 2011, and 2020 experienced strong monsoon performance during La Nina conditions.

EL NINO & LA NINA EFFECTS ON GOA’S MONSOON (June–September)
Goa sits on the west coast of India, so it gets very heavy southwest monsoon rainfall from moisture-laden winds coming from the Arabian Sea. Because of this coastal position, ENSO effects (El Nino/La Nina) are felt, but not always in a simple ‘dry vs wet’ way.

EL NINO IMPACT ON GOA

• Rainfall often becomes slightly below normal or more uneven


• Delayed or weaker monsoon bursts at the start (June)


• More breaks in rainfall (dry gaps between rainy spells)


• Fewer extremely widespread heavy-rain days, but still can get local intense showers


• Higher chance of hot and humid spells between rains

Goa usually does not turn ‘dry’ even in strong El Nino years. Because it is directly exposed to Arabian Sea monsoon winds, it still receives substantial rainfall — but variability increases.

LA NINA IMPACT ON GOA

• Above-normal rainfall more likely


• Stronger and more persistent monsoon winds


• Frequent heavy rainfall spells (very intense rain events)


• Higher risk of flooding in low-lying areas as well as landslides in Western Ghats regions nearby


• Fewer long dry breaks during monsoon

FOR THE RECORD
Records show that Goa's driest El Nino year was 1972, when the state experienced a 47.3% deficit in monsoon rainfall, the largest shortfall observed during any El Nino year on record.

The 2020 southwest monsoon season was the wettest documented La Nina-influenced monsoon period in Goa in more than a century. The state received approximately 4,118 mm (411.8 cm or 162.1 inches) of rainfall, marking the highest monsoon rainfall recorded in Goa since at least 1920.

IN SUMMARY
El Nino generally weakens India's monsoon and can lead to rainfall deficits, while La Nina generally strengthens the monsoon and increases rainfall, though other climate factors can modify these effects.