Positive IOD in the horizon, may ease impact of Super El Niño, improve monsoon prospects, says weather expert

CHENNAI: In what would come as a sliver of relief to all, from farmers and scientists to governments and businesses, atmospheric scientists are now predicting a partial relief from the ongoing Super El Niño conditions and better prospects for the seasonal rainfall over Tamil Nadu and other parts of south India to be near-normal, thanks to the increasing likelihood of another weather phenomenon called the positive Indian Ocean Dipole (IOD).

The IOD is a climate phenomenon characterised by contrasting sea surface temperatures across the equatorial Indian Ocean. During a positive IOD phase, the water near the western Indian Ocean, close to Africa, becomes warmer than average, while the eastern Indian Ocean waters, near Indonesia, become relatively cooler. This temperature contrast alters atmospheric circulation and influences rainfall patterns across the region.

Speaking to DT Next, Dr VR Durai, Director of the Regional Weather Forecasting Centre at the Regional Meteorological Centre, Chennai, said observations indicate that ocean temperature patterns over the Indian Ocean are gradually becoming favourable for the development of a positive IOD.

"A positive IOD is identified when the eastern parts of the Indian Ocean become about 0.5 to 0.6 degrees Celsius warmer than normal. We are now observing changes in sea surface temperatures over the eastern Indian Ocean, and there is a growing possibility that a positive IOD could develop," he said.

While a positive IOD would not completely offset the effects of the ongoing Super El Niño, which remains one of the strongest global climate events, it could increase the monsoon rainfall by around one to two per cent, helping the season remain closer to the normal range, said the atmospheric scientist.

"It will not fully nullify the impact of the Super El Niño, which is a massive climatic phenomenon. However, it can provide some relief by supporting better seasonal rainfall than what we would have expected under strong El Niño conditions," he said.

The looming possibility of a deficit monsoon was one of the major concerns for the agriculture sector in India, and by extension, for the governments at the State and central levels, and also businesses that look forward to beneficial – or at least near-normal – monsoon seasons. The Super El Niño condition accentuated the risks, as countries have faced catastrophic impacts whenever the phenomenon happened in the past.

Meanwhile, speaking about the recent heavy rainfall witnessed across Kerala and the Arabian Sea coastal area, he said the key reason for this was the strong cross-equatorial winds known as the Somali Jet, which are blowing at speeds of around 40 to 50 knots. “These low-level jet winds transport large amounts of moisture into the Arabian Sea and play a crucial role in strengthening the southwest monsoon," he explained.