Amid the peak monsoon season, the Indian Ocean Dipole (IOD) has emerged as a critical climate phenomenon that could significantly influence India’s southwest monsoon. Characterised by the difference in sea surface temperatures between the western and eastern parts of the Indian Ocean, the IOD plays a pivotal role in shaping rainfall patterns over the subcontinent.
During years when El Niño develops in the Pacific Ocean, monsoon rainfall over India typically weakens. This occurs as atmospheric circulation shifts away from the region, reducing moisture transport to the Indian landmass. A stronger “super El Niño” can intensify this effect by further disrupting monsoon winds and suppressing rainfall.
In such years, the phase of the IOD becomes particularly important. A positive IOD, marked by warmer waters in the western Indian Ocean and cooler waters near Indonesia, can enhance moisture flow towards India. This helps partially offset the adverse impact of El Niño and supports better monsoon rainfall. In contrast, a negative IOD reinforces El Niño’s drying influence by pulling moisture away from the subcontinent, raising the risk of below-normal rainfall. The interaction between these two ocean phenomena is thus a decisive factor in determining the strength and distribution of the monsoon.
‘If IOD becomes positive, it could offset some stress’: Expert
According to Dr Anguluri Suryachandra Rao, Director of the Indian Institute of Tropical Meteorology (IITM), Pune, a positive IOD may help soften El Niño’s impact this season. Speaking exclusively to ETV Bharat, Rao explained that warmer waters in the western Indian Ocean and cooler waters in the east can draw more moisture toward the subcontinent, improving the chances of rain even under active El Niño conditions.
“The key hope lies in the possibility that the IOD turns favourable later in the monsoon, which could help the second half of the season recover,” he said to ETV Bharat. Rao’s assessment underscores that the monsoon outlook is not determined by El Nino alone. It will also depend on how the Indian Ocean evolves in the coming weeks.
“If the IOD becomes positive, it could offset some of the stress caused by the Pacific warming and give India a better rainfall outcome than initially expected. If not, the combined impact of El Niño and an unfavourable dipole could leave the monsoon vulnerable to extended dry spells and uneven rainfall,” he added.
Rao explained that during the major 1997 El Nino, the monsoon impact was significantly reduced because a dipole occurred at the same time. He also said the current El Nino has arrived early and is already disrupting rainfall distribution, but that India would be “safe” if the monsoon gains momentum over the next month or two. The IMD currently sees the IOD as neutral, but expects positive conditions later in the season, which could help salvage the latter half of the monsoon. He added that the big uncertainty is timing. The hope is not that the dipole can rescue early monsoon months already affected by El Niño, but that it can improve rainfall later in the season, he said.
How will IOD impact the monsoon?
The Indian Ocean Dipole, or IOD, is a climate pattern defined by the temperature difference between the western and eastern parts of the Indian Ocean. When the IOD turns positive, warmer waters in the west and cooler waters in the east draw more moisture toward India, which can support rainfall and partially offset the drying influence of El Niño on the monsoon. In simple terms, a positive IOD often acts as a buffer for the season.
A negative IOD works in the opposite way, pushing moisture away from the subcontinent and, if it coincides with El Niño, can make an already weak monsoon even drier. The IMD currently sees the IOD as neutral, but expects positive conditions to develop later in the season, which means the key hope is not for immediate relief in June and July but for improvement in the second half of the monsoon.
El Nino monitoring system on high alert
Union Agriculture and Farmers’ Welfare Minister Shivraj Singh Chouhan earlier said the government has fully activated its monitoring mechanism in view of the possible impact of El Niño on the monsoon. He noted that the El Nino Monitoring Cell, the Crop Weather Watch Group, state control rooms and designated officers are continuously tracking monsoon progress, sowing activity, crop health and market conditions.
Shivraj Chouhan said the government is not just watching the situation but is also prepared to respond to any challenge with strong systems, adequate resources and a time-bound action plan. He stressed that the focus is on proactive management so that any disruption to agriculture can be addressed quickly and effectively.