Strong winds keep Delhi’s AQI in ‘moderate’ for 2nd day

The IMD has issued a yellow alert for Tuesday, forecasting one to two spells of light rain during the day, with gusty winds of up to 40km/hr – which will also keep Delhi’s air quality in check.

Strong northwesterly winds continued in the city on Sunday, improving the air quality to record the cleanest January air in Delhi in four years, as per data by the Central Pollution Control Board (CPCB).

Delhi witnesses improved air quality with cloudy skies seen at Samalkha t-point area on Sunday. (Parveen Kumar/HT PHOTO)

The 24-hour average air quality index (AQI) was in the “moderate” category on Sunday, with the 4pm reading at 153, an improvement from Saturday’s 4pm reading of 193.

However, forecast by the Centre’s Air Quality Early Warning System (EWS) for Delhi, shows the AQI is likely to dip to “poor” on Monday, before returning to “moderate” by Wednesday. “Delhi’s AQI is likely to be in the ‘poor’ category from January 26-27. It is likely to be in the ‘moderate’ category on January 28,” said the EWS in its daily bulletin. Between January 29 and February 3, the AQI will oscillate between “moderate” and “poor” zones, the system mentioned.

Further, the India Meteorological Department (IMD) has issued a yellow alert for Tuesday, forecasting one to two spells of light rain in the city during the day, with gusty winds of up to 40km/hr – which will also keep Delhi’s air quality in check.

The CPCB classifies air quality as “moderate” when the AQI is between 101 and 200, “poor” between 201 and 300, and “very poor” between 301 and 400. Beyond 400, air quality is termed “severe”.

The respite comes after a three day streak of 400+ AQI just last week, from January 17 to 19. The latest western disturbance and rain on January 23 provided relief from high pollution levels.

In December, similarly, Delhi saw alarming pollution levels, with five “severe” air days. There were three such days in November. Typically, meteorological conditions start to become favourable for dispersion of pollutants from February onwards, as temperature starts to rise.

Meanwhile, the impact of the western disturbance from January 22-24, is still being felt in the region, with icy-cold northwesterly winds blowing from the freshly snow-capped upper Himalayan region, towards the plains.

Delhi’s minimum temperature stood at 6.6 degrees Celsius (°C) on Sunday – a notch below normal and down from 7.6°C on Saturday. The minimum is expected to hover around 4-6°C on Monday as cold northwesterly winds continue, before rising once again and hovering between 8-10°C on Tuesday, experts said.

“When a western disturbance approaches, it causes a change in wind direction, to warmer easterly winds. Overcast skies also lead to a rise in minimum temperature and a dip in maximum temperature,” said Mahesh Palawat, vice president at Skymet.

Fresh spell of snowfall is expected through this western disturbance, resulting in a dip in minimum temperature across the plains from January 29, Palawat said.

Delhi’s maximum temperature stood at 18.5°C on Sunday – two degrees below normal for this time of the year. It was 18.2°C on Saturday. The maximum is expected to hover between 19-21°C on Monday, before dipping to 18-20°C on Tuesday.