Delhi’s AQI improves to ‘moderate’; drizzle likely in national capital tomorrow

The temporary change in wind directions has raised the night-time temperature, with the possibility of a drizzle in parts of Delhi on Tuesday

After two consecutive “poor” air days, the Capital’s pollution levels significantly improved to reach the “moderate” category on Sunday, thanks to a shift in wind directions—from northwestern to southwestern—the India Meteorological Department said. However, weather officials also attributed the improvement in air quality to Stage I of the Graded Response Action Plan (Grap) measures being implemented, when the air quality had hit the “poor” mark on Friday.

Smog in the early hours at Kartavya Path in New Delhi on Sunday. (Sanchit Khanna/HT Photo)

An IMD official said the temporary change in wind directions has made the skies cloudy and raised the night-time temperature, with the possibility of a drizzle in parts of Delhi on Tuesday.

The 24-hour average air quality index (AQI) was recorded at 164 on Sunday, which was 216 (poor) on Saturday—a notable 50-point drop, according to data from the Central Pollution Control Board (CPCB).

Officials said that though this meant that Stage 1 Grap measures could now be removed, the Commission for Air Quality Management (CAQM) said it would not do so, since the implementation of Grap was one of the reasons behind the improvement in air quality.

Meanwhile, air quality in the national capital region largely remained in the “moderate” zone on Sunday except for Greater Noida, which recorded an AQI reading of 249 (poor). Noida recorded 147, Ghaziabad 154 and Gurugram 171 (all moderate), according to CPCB.

“It appears that Stage I of Grap and the control measures have played a role in this improvement. Stage-I needs to remain in place to allow such air quality to continue to prevail in the region,” said VK Soni, scientist at IMD and part of the CAQM’s sub-committee that implements Grap.

Twenty-seven measures fall under Stage 1 of Grap, which were rolled out by CAQM on Friday including barring unregistered construction sites, taking strict action against visibly polluting vehicles, and stepping up PUC checks, among other things.

Forecast by the Early Warning System (EWS) for Delhi, a forecasting model under the ministry of earth sciences, showed that AQI will likely remain in the “moderate” zone till Tuesday, before returning to “poor” once again by Wednesday.

Before Sunday, Delhi had been recording cold northwesterly winds, which not only aided in the transportation of smoke from the farm fields in Punjab and Haryana, where stubble-burnng has begun, but also helped bring down the mercury. On Sunday, following a change in wind direction, the minimum temperature rose and was recorded at 23.1 degrees Celsius (°C), which was two degrees above normal for this time of the year. It was 20.9°C on Saturday and 18.6°C a day earlier.

Delhi’s maximum was recorded at 36.5°C—two degrees above normal.

“We expect the minimum to remain around 23-24°C till Tuesday. From Wednesday, northwesterly winds will return and the minimum is expected to drop again,” said the official.