Researchers call cold wave-like situation in Karnataka a rare event, attribute it to La Nina

Bengaluru: The researchers from Bengaluru University and the India Meteorological Department (IMD) Bengaluru have termed the cold wave like situation in Karnataka over the last week 'a rare event.'

“The week of December 8 to December 14 came as a meteorological shock that sent shivers from the frost-tipped landscapes of Bidar to the foggy streets of Bengaluru. It was a rare and intense cold wave that rewrote the climatological script for the decade,” the researchers noted in an analysis.

Analysing the situation, they attributed the event to La Nina conditions and Siberian wind. The La Nina conditions resulted in cooler-than-average sea surface temperatures and acted as a conductor for the planetary weather orchestra by strengthening the trade winds and modifying the global circulation pattern, they said.

Explaining how the Siberian winds had a major role to play, the analysis noted that they were blocked by the Himalayas and as a result, air escaped out of its usual boundaries. Siberian High is a massive, semi-permanent collection of cold, dry air that accumulates over northern Asia.

“A perfect synoptic storm facilitated this southward migration of cold air. A robust high-pressure cell established itself over Central India, while a weak low-pressure area loomed over the Bay of Bengal. Nature abhors a vacuum, and air naturally flows from high to low pressure; this gradient acted like a giant funnel, driving dry northerly winds deep into the heart of Peninsular India,” the researchers said.

The data recorded by the India Meteorological Department during this week showed that the North Interior Karnataka was bearing the brunt of this climatological changes as Vijayapura recorded seven degrees Celsius and Bidar touched 7.4 degrees Celsius, nearly 8 degrees Celsius less than the normal.

Even Bengaluru, usually insulated by its urban heat, saw temperature at the airport plunge to 12.9 degrees Celsius.

While the winds brought the cold air to Karnataka, the extreme severity of the freeze was dictated by the microscopic physics of the boundary layer, specifically a process known as nocturnal radiative cooling. Still air also had a role to play, the researchers said.

The analysis was published by Professor Kamsali Nagaraja, Department of Physics, Bangalore University and Chanabasanagouda S Patil, Scientist, IMD Bengaluru.