January 2024 saw bitter cold engulf Delhi and other parts of India. Delhi experienced five cold waves, with its nights being the coldest since 2013 and days since 2003. In contrast, in December, the city was at its warmest in six years with not a single cold wave that month.
Temperature drops
What is a cold wave? Broadly speaking, it is defined as an extreme weather event marked by a negative departure (a drop in average temperature) well below the average for that region for a sustained period of two days or more. India’s core cold wave zone covers the northern, central and eastern parts. But the west and south come in for spells too.
According to the Indian Meteorological Department, a cold wave occurs when the minimum temperature is 10°C or less for plains and 0°C or less for the hilly regions and negative departure from normal day temperature is 4.5 to 6.4°C. If negative departure is more than 6.4°C, it is a severe cold wave. Which means that day temperatures play an important role in cold waves.
Additionally, the plains suffer a cold wave when minimum temperature is 4°C or less and a severe cold wave when minimum temperature falls to 2°C or less. Coastal areas suffer cold waves when the minimum temperature is 15°C or less and the negative departure from the minimum is 4.5 °C.
New Delhi, Jan 15 (ANI): A view of the Mehrauli-Gurugram road covered in dense fog as the cold waves continue on a cold winter day, in New Delhi on Monday. (ANI Photo) | Photo Credit: ANI
Dr. Attada from IISER Mohali explained that cold waves in India were considered to be influenced by ‘Western disturbances’ or cold winds starting from the Mediterranean across the Caspian Sea and blowing into India across Afghanistan-Pakistan. However, recent research shows that a phenomenon called ‘Arctic amplification’ — coming all the way from the Arctic and Siberia — descends upon India to cause extreme cold events. He added that the global weather phenomenon ‘la Nina’, with its cold winds all the way above the Eastern Pacific, also influences cold wave conditions across India. There is another phenomenon called ‘wind chill factor’ whose chilly winds make you feel a few degrees colder than what the thermometer may show!
Serious issue
Cold waves are a serious weather phenomenon that kill people, often even more than a heat wave. Other than being careful, be sensitive to the needs of those forced to work outside for long hours like watchmen, gardeners, labourers, farmers, housemaids, drivers. We can help them by giving them leave on days of extreme cold, changing working hours to sunlight hours, and providing them with warm workspaces, warm fluids, and multiple layers of warm clothes.
Just think that the cold making you shiver may have come to you from the Caspian Sea, or the Pacific Ocean or even all the way from the Arctic!
