Cold wave continues to grip Delhi, Ayanagar records season’s lowest temp at 1.8°C

A cold wave continued to grip Delhi on Friday with the Ayanagar recording a minimum temperature of 1.8°C, the lowest for any weather station in Delhi this season, even as the air pollution levels remained in the “very poor” category.

Ayanagar earlier recorded the lowest temperature in the city this season at 2.2°C on Thursday. Safdarjung, which is representational of Delhi’s weather, recorded a low of 4.0°C on Friday morning. It was three degrees below normal but a degree higher than Thursday’s minimum of 3°C, Delhi’s coldest in nearly two years.

On January 26, 2021, a minimum of 2.1°C was recorded at Safdarjung. A low of 1.1°C was recorded on January 1 of that year, the lowest minimum for Safdarjung in the last decade.

A cold wave is declared in the region when the minimum temperature is 4.5°C or more below the normal mark, or when it drops to 4°C or lower. The mercury plunged to 3.8°C at Lodhi Road and 3.3°C at the Ridge on Friday.

The maximum temperature was likely to be around 17°C on Friday compared to 16.5°C, three notches below the normal, on Thursday.

Delhi has been colder than several hill stations as dense fog engulfed Delhi and the rest of north India and impacted several flights and trains on Thursday. The fog stretched from Punjab up to Bangladesh and led to extremely low visibility during the morning hours.

About 50 flights were delayed between 3.30am and 9am on Thursday. At least 12 trains were delayed by two hours or more.

The dip in mercury has led to increased power consumption. The peak demand was clocked at 5,247MW at 10.56am on Thursday, the highest winter demand for Delhi in three years. It touched a peak of 5,343MW in the winter of 2019-2020.

IMD issued a “yellow alert” for the national capital for Friday, predicting cold wave conditions to continue. Dense fog is also expected on Saturday and Sunday.

The minimum temperatures have has dipped sharply across north India by 1-3°C due to cold northwesterly winds. The mercury is expected to gradually rise again, touching 5°C on Saturday and 6°C by Sunday.

A western disturbance was expected to influence the northern plains on January 7 and 8 and the minimum temperature will hover around 8°C. The maximum temperatures are likely to rise gradually to 18°C by Saturday and 20°C by Monday.

“Cold day” to “severe cold day” conditions were likely in pockets in Delhi, Punjab, Haryana, and Uttar Pradesh until the weekend. Low moisture created conditions for the persistence of a layer of dense fog this week. Winds were expected to pick up and lead to a reduction in intensity and extent of fog and also “cold day” conditions gradually from Friday.

According to the Central Pollution Control Board, the hourly Air Quality Index (AQI) was 369 at 7:30am on Friday. The average 24-hour AQI was 340 at 4pm on Thursday.

An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, 301 and 400 very poor, and 401 and 500 severe. The AQI in the poor category leads to breathing discomfort for most people on prolonged exposure.

Monitoring agency System of Air Quality and Weather Forecasting and Research said fine particles (size < 2.5 micrometer) contributed ~ 63% to PM10. “For the next 3 days, surface wind speed (calm to 8 km/h) and temperature (Max 17-18 deg C; Min 3-4 deg C) are likely to worsen air quality.”

Mixing layer height was likely to be ~ 1.0 km which helps dilution of pollutants. “Air quality is likely to deteriorate but within ‘very poor’ for the next 3 days due to low temperature (helps accumulation of pollutants) and low surface winds (reduces the dispersion of pollutants).”