Dense fog in Delhi; air quality remains ‘very poor’

The minimum temperature on Tuesday is likely to be at 6°C while maximum temperature is predicted to reach 22°C while the air quality levels of the city were in very poor category at 7:00am

Delhi is likely to see dense fog in the morning with mainly clear sky during the day on Tuesday, the India Meteorological Department (IMD) said.

IMD also forecasts the maximum temperature to dip further in the coming days. (File image | Representative)

The minimum temperature on Tuesday is likely to be at 6°C while maximum temperature is predicted to reach 22°C while the air quality levels of the city were in very poor category at 7:00am.

The minimum temperature on Monday was 7.2°C, one notch below normal and maximum temperature was 23.2°C -- one degree above normal.

The humidity levels over the last 24 hours have varied between 49% to 97%.

On Monday, the national Capital saw first dense fog spell of the of the season.

IMD has also issued a yellow alert until December 23 now, forecasting moderate to dense fog to continue in Delhi. While dense fog is expected on Tuesday and Wednesday morning, moderate to dense fog is expected on Thursday.

On Friday, the IMD forecasts dense fog once again in the morning.

A yellow alert is generally issued to inform the public about a weather phenomenon.

IMD also forecasts the maximum temperature to dip further in the coming days. While the maximum is likely to bring around 22°C on both Tuesday and Wednesday, it will be around 21°C on Thursday.

Fog is termed as ‘smog’ when pollution levels are already high, and the pollutants combine with moisture to reduce visibility. This happens when the moisture in the air traps pollutants closer to the surface, and the low temperature and calm winds make it difficult for the pollutants to disperse.

Experts said while the overall weather phenomenon across the Indo-Gangetic plains where visibility dipped below 200 metres can be classified as dense fog formation, in Delhi-NCR, pollution levels were already fairly high and this entails there was actually smog that was prevalent across NCR.

On the pollution front, Delhi’s air quality was in the very poor category on Tuesday morning. Data from the central pollution control board showed that the hourly air quality index (AQI) at 7am stood at 382.

On Monday, the average 24-hour AQI had been 410, which is in the ‘severe’ category.

An AQI between zero and 50 is considered ‘good’, 51 and 100 ‘satisfactory’, 101 and 200 ‘moderate’, 201 and 300 ‘poor’, 301 and 400 ‘very poor’, and 401 and 500 ‘severe’.

On Tuesday, the union ministry of earth science’s air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (Safar) said, “The overall air quality index indicates very poor air quality due to the occurrence of radiative fog as a result of low temperature and nearly saturated (more than 95%) relative humidity. Fine particles (size less than 2.5 micrometer) contribute around 56% to PM10.”

SAFAR has added that for the next 3 days, surface wind speed (8 to 16 km/hour) and temperature (between the minimum of 7°C and maximum of 23°C) are likely to increase the air quality index. Mixing layer height is likely to be around 1.0 km that helps dilution of pollutants. Air quality is likely to deteriorate for the next 3 days due to relatively low temperatures and moderate wind speed resulting in weak to moderate dispersion of pollutants”.