Post-Diwali air quality conditions in Delhi: What to expect

November 1, the day after Diwali, will present more favourable meteorological conditions for dispersing pollutants. With expected high daytime temperatures reaching around 35 degrees Celsius and night temperatures at about 20 degrees, there is potential for aiding the dispersion of particulate matter.

In Short

• Delhi's post-Diwali weather may aid pollutant dispersion
• High daytime temperatures of 35 degrees expected to help
• Low wind speeds on Thursday night may hinder dispersal

Just as Diwali approaches, there is a keen interest in understanding how the prevailing weather conditions will affect pollution levels in Delhi, keeping in mind the worsening air quality levels due to the bursting of firecrackers. While the city's overall meteorological conditions offer a mixed outlook, a detailed analysis, however, provides some insights and predictions.

November 1, the day after Diwali, will present more favourable meteorological conditions for dispersing pollutants. With expected high daytime temperatures reaching around 35 degrees Celsius and night temperatures at about 20 degrees, there is potential for aiding the dispersion of particulate matter.

The heat during the day can enhance the dispersal processes, allowing pollutants to dissipate more effectively than usual.

However, Thursday night and Friday morning are predicted to pose challenges for air quality management. The relatively calm wind speeds, expected to be around 8 km/h, are insufficient for the swift dispersal of pollutants, likely allowing pollution from fireworks to linger until the wind speed picks up to 16 km/h later in the morning.

In addition to the temperature and wind speed, two critical factors influencing pollutant dispersal are the mixing depth and the ventilation index.

Fortunately, Delhi's mixing depth on Thursday is anticipated to be about 2,280 meters. This indicates that pollutants will mix higher in the atmosphere, which can aid in preventing the concentration of pollutants near the ground.

Moreover, the ventilation index is projected to be 21000 m²/s, significantly above the favourable threshold of 6000 m²/s, suggesting a robust potential for pollutant dispersion.

So, while the Diwali night might see temporary pollution accumulation, the following day holds promise for a better air quality outlook in Delhi. The combination of predicted meteorological factors offers some respite, urging residents to remain hopeful yet cautious.

DELHI RECORDS 2ND HOTTEST DAY IN OCTOBER

On Wednesday, the eve of Diwali, Delhi recorded the second-hottest day this month.

The national capital registered the second-highest maximum temperature of October at 36.1 degrees Celsius, 5.1 degrees above normal, according to the India Meteorological Department (IMD).

The highest temperature of the month was recorded on October 19 at 36.2 degrees Celsius.

Meanwhile, the city's 24-hour average Air Quality Index (AQI) was recorded at 307 at 4 pm on Wednesday, according to data from the Central Pollution Control Board (CPCB).

Out of the 40 monitoring stations, two -- Anand Vihar and Mundka -- were in the "severe" category with AQI levels above 400.

On Thursday, the IMD forecast mist in the morning with a clear sky during the day.

The maximum and minimum temperatures are expected to settle around 36 degrees Celsius and 21 degrees, respectively.

(With inputs from PTI)