Today's Editorial

Today's Editorial - 22 January 2023

Why is northwest India shivering?

Source: By The Indian Express

Delhi and other parts of northwest India have been reeling under a cold wave spell that set in last week.

In Delhi, the Safdarjung weather station, which provides representative figures for the city, has recorded cold wave conditions for five consecutive days so far this month, making it the longest such spell in a decade. The lowest minimum temperature recorded this month was 1.9 degrees Celsius, the second-lowest minimum temperature in January in 15 years.

While lower-than-normal temperatures were recorded over parts of Northwest India from the last week of December, these conditions intensified in the first week of January. Fog and low cloud coverage brought severe cold day conditions to the region, when temperatures remained below normal over parts of Delhi, Punjab, Haryana, Chandigarh, Himachal Pradesh, Rajasthan, Uttar Pradesh and Madhya Pradesh.

What is a cold wave?

The IMD marks a cold wave in terms of minimum temperatures – when the minimum temperature in the plains is 4 degrees or less or when the minimum temperature is less than 10 degrees and 4.5 to 6.4 degrees below the normal.

One of the major factors contributing to colder than normal temperatures over north India this month is the large-scale fog cover, according to RK Jenamani, scientist, IMD. “While westerly and northwesterly winds of around 5 to 10 kmph in the afternoon have also been contributing to the dip in temperature, an important factor this month is fog, which has been lasting for longer durations, preventing sunlight from reaching the surface and affecting the radiation balance. There is no heating in the day time, and then there is the impact of the night. Foggy or cloudy nights are usually associated with warmer nights, but if the fog remains for two or three days, cooling begins even at night,” he explained.

Light winds and high moisture near the land surface have been contributing to the formation of a blanket of fog over large swathes of the Indo-Gangetic plains in the morning.

Since there has not been any significant impact of western disturbances over the region, cold northwesterly winds have also been contributing to low temperatures. Western disturbances, which are storms from the Mediterranean region, are associated with a change in wind direction, bringing easterly winds to northwest India. The last time the region saw easterly winds was on 29 December, Jenamani said.

Delhi usually records cold wave spells in December and January. Over the past decade, the number of cold wave days in January has ranged from none to seven. While there were no cold wave days in December in Delhi this winter, the five such days so far this month are more than January last year, when there were no cold wave days, IMD data shows. In January 2021, there were 7 days when the minimum temperature was 4 degrees or less, but they were not consecutive. A similar long spell was recorded in 2013, when there were 7 consecutive cold wave days, Jenamani said.

What is the forecast for the week ahead?

Cold wave conditions abated over parts of northwest India on 10 January 2023, with the minimum temperature in Delhi rising to 6.4 degrees Celsius.

With a western disturbance affecting northwest India, the minimum temperature is set to rise by 2 to 4 degrees over the plains of northwest India over the next three days, according to an update issued by the IMD on 10 January 2023. While dense fog is likely to persist over parts of Punjab, Haryana, Delhi, Chandigarh and Bihar over the next 24 hours, it could abate thereafter, before making a comeback on 14 January, the forecast indicated.

In Delhi, the maximum temperature, which saw a low of 16.1 degrees Celsius last week, could rise to around 20 degrees Celsius by 12 January. The minimum temperature, meanwhile, could climb to around 9 degrees by 12 January.