Delhi’s air quality registers as poor, thin chances of any improvement soon

Last updated on February 17th, 2023 at 12:59 pm

Tuesday air quality in Delhi recorded further deterioration of “very poor” category for majority of the day. This was primarily due to change in weather conditions which made it unfavourable. Wind speed over the capital recorded a drop to near zero between Monday 7 pm and Tuesday 8 am. The temperature during night was recorded as 19.8C by India Meteorological Department. These change in weather conditions led to a fall in atmospheric mixing layer or the vertical height which has pollutants suspended. This led the particulate matter concentration of 2.5 micrometers (PM 2.5) and 10 micrometers (PM 10) to exceed double mark overnight. These fine particles when suspended in air can pose hazard of entering bloodstream through breathing.

Data released by Central Pollution Control Board (CPCB), Delhi on Tuesday recorded the AQI (average quality index) as 300 which was on ‘poor’ and ‘very poor’ levels.

In Delhi, the development of strong surface-level inversion and sudden calm wind conditions led to a low ventilation coefficient and accumulation of pollutants near the surface

SAFAR air quality

Central Government’s SAFAR air quality and weather forecasting system said in a forecast, “In Delhi, the development of strong surface-level inversion and sudden calm wind conditions led to a low ventilation coefficient and accumulation of pollutants near the surface.”

To understand the forecast in details, inversion can be defined as when surface temperature is lower than that at a higher altitude. This caps air’s upward movement and thereby disrupts diffusion of pollutants that are trapped near surface. Similarly, ventilation coefficient (VC) is sum of mixing layer and average wind speed. A VC below 6000 sqm/second is not favourable to allow dispersion of pollutants. The forecast in Delhi is to register this VC till Thursday.

Delhi government official said, “All the industries have been running on CNG, there is no sudden surge of vehicles on road and traffic congestion is also not very high. We are also constantly monitoring dust emissions at construction sites and imposing fines for non-compliance of norms.”

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Similar air quality is to be expected for next couple of days in Delhi due to calm wind condition during night time.