Delhi’s minimum temperature drops to 3.3°C, but some pollution respite

The chill and fog are both unlikely to relent over the next few days, said IMD as it issued an orange alert over Delhi for Tuesday and Wednesday

Delhi was ensnared in a cold wave for the fourth straight day on Monday, as the minimum temperature dipped to a season’s low of 3.3°C and brought with it another spell of blinding fog that continued the unending despair for people using mass transit services.

Children head to school on a cold, foggy morning near Dwarka in New Delhi. (Vipin Kumar/HT Photo)

However, breezier winds and an extended spell of sunshine in the afternoon helped pull Delhi’s air out of the “severe” zone, which pollution levels had breached on Sunday.

The chill and fog are both unlikely to relent over the next few days, said the India Meteorological Department (IMD) as it issued an orange alert over Delhi for Tuesday and Wednesday. An orange alert, which was also in place on Monday, warns people of inclement weather and of potential disruptions to everyday life.

Monday was the fourth straight day the minimum temperature fell to a low for this winter – it was 3.5°C on Sunday, 3.6°C on Saturday and 3.9°C on Friday.

IMD declares a “cold wave” when the minimum temperature is 4.5°C or more below normal. The agency can also declare a cold wave in the plains when the minimum reading is below 4°C, as has been the case in Delhi since Friday.

The bitter cold also brought with it another thick coat of smog, slashing the visibility at the Delhi airport to zero for nearly three hours in the morning and throwing flight services into disarray once more.

Met officials said Delhi reported dense fog between 2am and 8am. The visibility then dropped to zero between 3am and 5.30am.

As a result, around 100 flights entering or leaving Delhi’s Indira Gandhi International Airport were delayed on Monday, while five were diverted and around 20 were cancelled throughout the day. In fact, airport officials aware of the matter said Monday’s disruptions were, in part, also due to the knock-on impact of a string of delays on Sunday, when the season’s longest and most dense spell of fog hobbled operations well into the evening.

Trains were impacted as well, with at least 18 being delayed by over an hour, according to the Northern Railway.

IMD classifies fog as ‘shallow’ when visibility is between 500 and 1,000 metres; as ‘moderate’ when it is between 200 and 500 metres; as ‘dense’ when it is between 50 and 200 metres and ‘very dense’ when it is 50 metres or lower.

Kuldeep Srivastava, scientist at IMD, said no significant change in the weather is expected over the next 48 hours, with the minimum likely to hover in a similar range.

“An orange alert has been issued for cold wave conditions to continue. We will also continue to see dense to very dense fog in the early hours, which can impact flights, trains and road travel,” he said.

Delhi’s skies have been largely clear for the past few days, making for extremely cold nights, but warm days with bright sunshine.

The Capital clocked a maximum temperature of 19.7°C on Monday, around normal for this time of the year. It was 20.6°C a day earlier.

Clear skies allow for ample sunshine to reach the surface, raising the ambient air temperature. The same temperature starts to fall rapidly at night, as there are no clouds to trap heat within the atmosphere.

Relatively stronger winds, however, helped clear the air up to an extent on Monday. The 24-hour average air quality index (AQI) improved from 447 (severe) on Sunday to 359 (very poor) on Monday.

Sunday was Delhi’s first “severe” air day, prompting the Commission for Air Quality Management (CAQM) to invoke Stage 3 of measures under the Graded Response Action Plan (Grap), disallowing the use of BS-3 petrol and BS-4 diesel four-wheelers across Delhi, Gurugram, Faridabad, Ghaziabad and Gautam Budh Nagar.

Forecasts by the Early Warning System for Delhi — a forecasting model under the ministry of earth sciences, shows Delhi’s AQI is likely to remain “very poor” till January 18.