The air quality in the national capital region witnessed a significant improvement on Wednesday, leading authorities to roll back the most stringent anti-pollution curbs. The Commission for Air Quality Management (CAQM) revoked the Graded Response Action Plan (GRAP) Stage-IV restrictions after the Air Quality Index (AQI) dropped from the severe category into the very poor range.
Winds Bring Relief, Restrictions Eased
The decision to lift GRAP Stage-IV was taken as the AQI for Delhi was recorded at 271, in the 'poor' category, on December 24. This marked a drastic improvement from the 412 AQI recorded a day earlier. The commission cited forecasts from the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) indicating that the AQI is likely to remain between 'poor' and 'very poor' in the coming days.
The primary driver behind this improvement was identified as strong, dry winds that swept across the region. An IMD official noted that the peak wind speed reached 22 kmph in the south-west direction around 2 pm. These dry winds helped disperse accumulated pollutants, unlike humid or foggy conditions which tend to trap impurities.
What Changes Now?
With the immediate revocation of GRAP Stage-IV, BS-IV compliant petrol light motor vehicles (LMVs) from other states are now permitted to enter Delhi. However, it is crucial to note that all restrictions under GRAP Stage-III remain firmly in place across the Delhi-NCR. These include bans on non-essential construction work and the operation of BS-III petrol and BS-IV diesel LMVs within the region.
The CAQM stated that the decision considered the "disruptive nature of restrictions under Stage-IV" which impact a large number of stakeholders and the general public.
Meteorological Factors at Play
The improvement in air quality was accompanied by better visibility and a rise in temperatures. While dense fog in the early morning hours reduced visibility to as low as 100 meters at Palam between 2 am and 5 am, it improved to 400 meters at Safdarjung by 6:30 am and continued to get better through the day.
The city's minimum temperature settled at 10.2 degrees Celsius, with a maximum of 25.2 degrees Celsius. Analysts pointed out that the sharp reduction in PM2.5 levels—which fell to as low as 11 micrograms per cubic metre at some monitoring stations—was more attributable to stronger winds and better ventilation than to the GRAP measures themselves.
While the respite offers temporary relief, authorities continue to enforce GRAP-III measures, and the situation remains under close watch as meteorological conditions evolve.
