Courtesy weekend rain, Delhi sees cleanest January air since 2015

Aided by a rainy spell on the weekend, Delhi has already recorded two ‘satisfactory’ air days on Saturday (91) and Sunday (69), while it recorded another ‘moderate’ air day on Monday, when the AQI was 151

Delhi is experiencing the cleanest January air since 2015, with the air quality improving to the “moderate” category on Wednesday. The minimum temperature also rose as foggy conditions kept the effects of cold northwesterly winds at bay.

A view of the Akshardham temple, on Wednesday. (Amal KS/HT)

The Capital recorded an overall air quality index (AQI) of 191 (moderate), down from Tuesday’s reading of 224 (poor), as per the Central Pollution Control Board’s daily 4pm bulletin.

Aided by a rainy spell on the weekend, Delhi has already recorded two ‘satisfactory’ air days on Saturday (91) and Sunday (69), while it recorded another ‘moderate’ air day on Monday, when the AQI was 151. Before this, Delhi has never recorded a satisfactory air day in January and has never recorded more than two moderate air days in the month. Officials said this is the cleanest January air spell since the AQI data began to be recorded in 2015.

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 aftermath of the rainy spell is also expected to keep Delhi shrouded in moderate fog, with chances of isolated dense fog, said officials from the Indian Meteorological Department (IMD), attributing the high minimum temperature in the Capital to it.

Delhi recorded an increase in the minimum temperature over the last 24 hours, increasing to 8.2 degrees Celsius (°C) on Wednesday -- one degree above normal – up from 6.5°C on Tuesday. “There are two factors in play at the moment. Wind speed has dropped, which is not allowing colder winds from the mountains to reach Delhi. We are also recording upper-level fog and cloudy conditions due to high moisture, which is not allowing the minimum to drop too much at night,” said IMD scientist RK Jenamani.

The maximum temperature was 18.1°C -- two notches below normal — on Wednesday, and it is forecast to hover between 19-20°C for the rest of the week.

Delhi recorded ‘moderate’ fog at Palam on Wednesday, with visibility around 200-500 metres, and ‘shallow’ fog at Safdarjung with visibility ranging from 500-1,000 metres in the morning.

“We are forecasting moderate fog for the remainder of the week. The possibility of dense fog (when visibility drops below 200 metres) cannot be ruled out either,” said Jenamani.

Delhi’s air quality could meanwhile return to the lower end of the ‘poor’ category, with a low mixing height expected to reduce dispersion of pollutants.

“With the prevailing partially cloudy conditions, along with maximum temperature gradually rising and moderate wind speeds persisting, air quality is likely to touch ‘poor’ on Thursday and remain the same for the two days. From January 15, air quality is expected to improve due to high wind speed causing strong ventilation of near surface pollutants,” said the Centre-run System of Air Quality And Weather Forecasting And Research (Safar).