What led to unusually low temperature at Ooty’s Fingerpost? Premium

At around 7 a.m. on January 14, as the day before Pongal dawned on Udhagamandalam, a local temperatu

At around 7 a.m. on January 14, as the day before Pongal dawned on Udhagamandalam, a local temperature gauge measured a frigid ground temperature of –6.3 degree celsius in the Fingerpost locality. The Government Botanical Garden said it was sprinkling water on the ground and covering flowering plants with another bushy plant to remove the rime.

The ground in other parts of Udhagamandalam had reached subzero temperatures as well. The lowest ambient temperature in the day was a more tolerable 1.7 degree celsius. What had caused the mercury to dip so low in Fingerpost?

The answer, as is often the case with the weather in the 21st century, begins somewhere else on the planet: the equatorial Pacific Ocean.

“We are in a La Niña winter,” Raghu Murtugudde, a visiting professor at IIT Bombay and an emeritus professor at the University of Maryland, said. This means heady winds blow warm water on the sea surface away from the South American mainland, roughly off the coast of Ecuador.

This heat movement across the Pacific has global consequences. Over India, the La Niña can intensify summer monsoons, bring excess rainfall, and cause colder winters.

In early 2022, the World Meteorological Organisation said the ongoing La Niña is the first in the 21st century to span three consecutive winters. But in a break from convention, the coldness is deeper in the south. This reveals the second driver.

La Niña is the opposite of El Niño, in which equatorial waters off the South American coast become unusually warmer. One effect is that in winter, the subtropical westerly jet over North India is pushed southward, allowing the western disturbance to create cold winters in the north. But in La Niña years, there is a ‘highway’ of chill wind coming southward from the Siberian High, “a cold, high-pressure block [of air] that is occupying the central Asian region and affecting winds coming into India,” says Prof. Murtugudde.