The Commission for Air Quality Management (CAQM) for the National Capital Region (NCR) on Wednesday decided to roll back the stringent Stage-IV restrictions of the Graded Response Action Plan (GRAP). This move came as the region's Air Quality Index (AQI) showed significant improvement, dropping from the severe category into the very poor range, largely due to favourable weather conditions.
Why Were The Restrictions Lifted?
The decision was taken after the AQI in Delhi witnessed a marked improvement from the night of December 23. The commission officially recorded the AQI at 271 on December 24, which falls under the 'poor' category. This was a substantial drop from the severe level of 412 recorded just a day earlier.
The CAQM sub-committee cited forecasts from the India Meteorological Department (IMD) and the Indian Institute of Tropical Meteorology (IITM) indicating that the air quality is likely to remain between 'poor' and 'very poor' in the coming days. Given the "disruptive nature of restrictions under Stage-IV" which affect a large section of the public and stakeholders, the panel unanimously decided to revoke this stage.
Immediate Impact on Travel and Construction
The immediate effect of this rollback is that BS-IV compliant petrol light motor vehicles (LMVs) from other states will now be permitted to enter Delhi. However, it is crucial to note that all restrictions under the preceding GRAP Stage-III remain firmly in place across Delhi-NCR.
This means bans on non-essential construction activities, the operation of BS-III petrol and BS-IV diesel LMVs within the region, and other associated curbs continue to be enforced. The commission's action is a graded response, scaling back only the most severe level of restrictions as the situation shows signs of improvement.
Role of Weather in Clearing the Smog
The dramatic improvement in air quality is primarily attributed to meteorological factors rather than pollution control measures. The IMD reported that strong, dry winds with a peak speed of around 22 kmph from the south-west and westerly directions helped disperse accumulated pollutants effectively.
An IMD official noted that while dense fog with visibility as low as 100 metres was recorded at Palam between 2 am and 5 am, conditions improved later, with visibility reaching 400 metres at Safdarjung by 6:30 am. The dry wind was a key factor, as humidity and fog typically trap impurities close to the ground.
This weather pattern also led to a sharp decline in the concentration of harmful PM2.5 particles. Data from the Delhi Pollution Control Committee (DPCC) showed hourly PM2.5 levels plummeting to as low as 11 micrograms per cubic metre in some areas. Analysts, including Manoj Kumar from the Centre for Research on Energy and Clean Air (CREA), pointed out that this reduction was "attributable to... stronger winds, rather than GRAP measures."
The city also experienced a rise in temperature, with the minimum at 10.2 degrees Celsius and the maximum reaching 25.2 degrees Celsius, aiding in better atmospheric ventilation.
What Happens Next?
The situation remains dynamic and heavily dependent on weather patterns. The CAQM's decision is contingent on continued forecasts of moderate wind speed, which prevents pollutant stagnation. Authorities will continue to monitor the AQI closely, and the GRAP stages are designed to be re-imposed if the air quality deteriorates back to the 'severe+' category.
The lifting of Stage-IV brings temporary relief, especially for inter-state transport, but the persistence of Stage-III rules underscores that the pollution battle is far from over. The episode highlights the critical, yet unpredictable, role that favourable meteorological conditions play in providing respite from Delhi's chronic winter air pollution crisis.
