Facts Box: Effects of El-Nino, Equinod and IOD on Indian Monsoon, 2019

The ongoing frenetic of the North-East Monsoon in the Peninsular India were supported by the same factors that propelled the South-West monsoon. The Indian monsoon of 2019 saw a neutral Pacific (neither El Nino nor La Nina), a positive Indian Ocean Dipole (IOD) and a positive Equatorial Indian Ocean Oscillation (EQUINOO).

El nino

  •  The variation in sea surface temperature drives the Indian Ocean and the Pacific phenomena and thereby Indian Monsoon.
  • The El Nino is a phenomenon in the equatorial Pacific where the temperature rises over a threshold of 0.5 degree Celsius. During El Nino the Equatorial East Pacific warms up relative to the west and has adverse impact on Indian monsoon.
  • The monsoon winds and rains are strong during La Nina and weak during El Nino. La Nina years bring heavy rains and El Nino years are dry.
  • Between 1950 and 2012, there were 16 La Nina years with monsoon rains ending up above or around average every time. Also, there were 14 other occasions. The 2002 was the driest monsoons in all these years when El Nino occured.
  • The weak El Nino in the Pacific Ocean this year is one of the reasons for rainfall deficit in the month of June.


In a positive IOD, the western basin of the Indian Ocean warms up creating a low pressure. This rises warm air clouds to set up storms and heavy rains in the South and South east Asia. A positive IOD aids in Indian monsoon. 2019 Monsoon witnessed a positive IOD


The positive EQUINOD translates more or less positive IOD. The Positive EQUINOD aids in North East Monsoon. 2019 monsoon witnessed a positive EQUINOD.