Delhi’s air quality ‘severe’ second day in a row; mercury expected to riseUpdated: Jan 02, 2020 23:51 IST
New Delhi: Air quality in the in the national capital was in the ‘severe’ category for the second consecutive day on Thursday. Calm weather conditions prevailed in the city, contrary to the forecast of strong winds. Meanwhile, emissions from local sources such as heavy vehicular traffic have kept pollution levels high over the past two days, according to figures released by pollution forecasting agencies.
The 24-hour average air quality index (AQI), as calculated by the Central Pollution Control Board (CPCB)’s 4pm bulletin, was 417 on Thursday, marginally lower than the 437 recorded the previous day. Delhi’s air quality has remained in the ‘severe’ zone since December 28, when AQI plunged to 409, barring December 31 when it improved to 387 or ‘very poor’.
The level of particulate matter (PM)2.5 – the most harmful of aerosols in Delhi’s air – was 280ug/m3 at 7pm, close to the emergency mark of 300ug/m3, while PM10 (coarse particles) was at 387ug/m3. The safe limits of PM2.5 and PM10 are 60ug/m3 and 100ug/m3.
However, as per the CPCB, pollution levels saw an improvement Thursday evening when the AQI came down to 409 at 6pm. “Pollution levels are expected to improve over the next two days, with a slight increase in wind speed resulting in better ventilation. Constant emissions from heavy traffic movement have added to the accumulation,” said a senior CPCB official.
The System of Air Quality and Weather Forecasting and Research (Safar), a Centre-run pollution and weather forecaster, also said in its forecast that calm weather conditions are persisting, during the night in particular, which has not allowed pollutant dispersion.
“Stable weather plus clustered emission hot spots, probably due to slow and congested traffic, lead to the accumulation of pollutants. Air quality is forecasted to improve to the higher-end of the very poor category on January 3-4,” said a senior Safar scientist.
Scientists at the India Meteorological Department (IMD) said that easterly winds have weakened the Western Disturbance (WD) which was expected to trigger high wind speed and light rainfall in the national Capital region.
“The effect of the WD has weakened, hence the lack of rain. The average wind speed too remained around 10kmph, which is not favourable for dispersion of pollutants. Also, wind speed dropping to zero during the night followed by dense fog in the morning allows pollutants to be trapped which, in absence of good wind speed, do not let up and remain suspended in the air,” said Kuldeep Srivastava, head, IMD’s regional weather forecasting centre.
However, light rain is expected around January 6-7, with another WD approaching the northwest region, which will help clear the air, he added.
“Another WD is expected around January 6-7, which will induce rain and snow. It is expected in the western Himalayan region, and will have an impact on Delhi as well,” added Srivastava.
In addition to this, dense fog cover will remain over the next three days, reducing visibility to less than 200 metres in the early hours. Besides, both day and night temperatures are expected to rise over the next two days due to easterly winds blowing over Delhi, he added.
After a record 18-day-long cold spell in December, the city saw a relatively warm day on Thursday with the maximum temperature settling at 23 degrees Celsius, three notches above normal. The night (minimum) temperature, however, remained low at 4.6 degrees Celsius, three notches below normal.