Delhi in smog grip, AQI ‘very poor’ for 13th day in a row

Slowing winds gripped the Capital in a blanket of smog on Monday, keeping the air quality index (AQI) at the “very poor” level for the 13th day in a row. Delhi recorded a 24-hour average AQI of 352, which was a marginal deterioration from an AQI of 334 (“very poor”) recorded a day earlier, according to the Central Pollution Control Board’s (CPCB’s) daily bulletin.
Experts said that winds with speeds of around 10 kilometre per hour (km/hr) were recorded over the weekend, but this dipped to around 4-6km/hr on Monday, trapping pollutants and making dispersion more difficult. Although a slight increase in wind speed is expected over the next three days, AQI is forecast to be “very poor” till Thursday.
CPCB classifies AQI between 0 and 50 as “good”, between 51 and 100 as “satisfactory”, between 101 and 200 as “moderate”, between 201 and 300 as “poor”, between 301 and 400 as “very poor”, and over 400 as “severe”.
The India Meteorological Department (IMD) said fog was reported in the early hours of the day, with smog reported in the second half of the day. The lowest visibility recorded was 700 metres, at the Safdarjung observatory, at 7 am.
According to IMD, foggy conditions are recorded if visibility is less than 1,000 metres and relative humidity is over 75%. If relative humidity is less than 75%, then it is termed smog.
“Mainly smog was reported in Delhi with wind speed less than 6 km/hr during the day. The wind direction was variable, meaning it kept changing,” an IMD official said, adding that wind direction will predominantly remain easterly for the next three days.
The contribution of stubble burning to Delhi’s PM 2.5 also declined. Data from the Centre’s Decision Support System (DSS) showed stubble burning accounted for 15.3% of Delhi’s pollution on Sunday — down from 16.75% recorded on Saturday and 20.55% recorded on Friday.
To be sure, the effect of stubble fires on the Capital peaks when the predominant wind direction is northwesterly.
According to CPCB, Delhi’s average AQI was calculated on the basis of 38 of 40 stations in the Capital. Both PM 2.5 (particulate matter having a diameter of 2.5 microns or less) and PM 10 (particulate matter having a diameter of 10 microns or less) were the lead pollutants throughout the day, which mainly constituted pollution from dust and combustion.
Among all stations, only the Jahangirpuri facility recorded a “severe” AQI reading, of 420 at 4pm.
Delhi’s overall AQI touched “very poor” on October 30 and has stayed in this range since. However, it has yet to deteriorate to the “severe” level this season.
Temperatures in the Capital, meanwhile, continued to remain above the normal levels. Both the maximum and minimum temperatures were three degrees above the normal for this time of the year. The minimum was 17.2 degrees Celsius (°C), down from 18.4°C recorded a day earlier. The maximum was 32.4°C, up from 31.6°C recorded a day earlier.
According to forecasts by IMD, the maximum temperature will hover between 32°C and 33°C over the next three days, and the minimum will stay in the 16-17°C range.