El Nino: Sea sub-surface temperatures up again from July-end, says US weather agency

Much to the concern of countries in Asia, particularly India, the equatorial sea surface temperatures (SSTs) were above average across most of the Pacific Ocean, indicating the setting in of the El Nino weather phenomenon.

(Sea) Subsurface temperature anomalies began to rise again in late July, though they decreased between mid-June and mid-July, the US National Oceanic and Atmospheric Administration’s Climate Prediction Center (CPC) said.

El Nino has a 95 per cent chance to be at its peak through December 2023–February 2024. “The tropical Pacific atmospheric anomalies are consistent with El Niño,” the CPC said in its latest update.

Positive SSTs

Over the past four weeks, equatorial SSTs were above average also across the western Indian Ocean and in the eastern and western Atlantic Ocean. “SSTs near Ecuador and Peru remain strongly above average,” the CPC said, adding that during the review period, mostly positive SST anomaly changes were evident in the central and eastern Pacific Ocean.

The weather agency said recent values of the “upper-ocean heat anomalies (above average) and thermocline slope index (below average)” reflect El Niño, which leads to drought and deficient rainfall in Asia.

“Positive subsurface temperature anomalies dominate most of the equatorial Pacific Ocean,” the CPC said.

The decrease in anomalies, probably, explains why India experienced above-normal rainfall in July. The rise in temperature is an indication of a hiatus in the south-west monsoon since the beginning of this month.

Deficient Indian SW monsoon

According to the India Meteorological Department, the entire country has experienced either deficient or “largely” deficient rainfall, barring Tamil Nadu and Jammu and Kashmir, in August.

Key kharif crops growing States have been deprived of rains this month, endangering pulses, cereals and oilseeds crop. The IMD has predicted that rainfall will likely resume in September.

However, the erratic weather pattern has begun to cast its shadow on the Indian economy with prices of agricultural commodities heading north and the Indian government clamping curbs on exports of rice, wheat and onions. 

Complex phenomenon

Two weeks ago, the Australian Bureau of Meteorology forecast warmer and drier conditions in the months to come. 

Bureau’s Senior Climatologist Catherine Ganter said, “Overall, the atmospheric indicators suggest the Pacific Ocean and atmosphere are not yet consistently reinforcing each other as occurs during El Niño events.”

It is a complex phenomenon that describes changes in the Pacific Ocean and the atmosphere above its, she said, adding that the US, Japan and Australia each have slightly different metrics for monitoring and declaring El Nino/La Nina Southern Oscillation (ENSO) events.

However, the Bureau said when El Niño Alert criteria have been met in the past, an El Niño event has developed around 70 per cent of the time. Each El Niño event has been different and its impact can vary.

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