Delhi’s air quality to deteriorate over two days due to adverse weather conditions

The air quality in the national Capital slipped back to the ‘very poor’ category on Monday after remaining in the ‘poor’ zone for two days. The air is likely to deteriorate over the next two days, Met officials predicted.

The Air Quality Index (AQI) value was recorded on Monday to be 336. On Saturday and Sunday it was recorded to be 249 and 261 respectively. On a scale of 0-500, AQI values between 201 and 300 are considered to be ‘poor’, values between 301 and 400 are considered to be ‘very poor’.

The Union government’s pollution forecasting agencies said that the air quality is likely to deteriorate further over the next two days, due to adverse meteorological conditions. Chances of breaching the ‘severe’ mark (AQI levels above 401) are, however, less this time, according to scientists.

“Strong winds had helped the pollution levels to go down over the weekend. But now that the winds are slowing down the pollution level is expected to shoot up again gradually,” said a scientist from the Central Pollution Control Board (CPCB).

This, however, is not the first time this season that air quality in Delhi will deteriorate due to adverse meteorological conditions. The AQI has been toggling between ‘poor’ and ‘very poor’ over the past few days.

“While on one hand the wind speed is expected to reduce to less than 10 km per hour, westerly winds are bringing in moisture. The air is getting heavier and slower which is why pollutants from local sources are getting trapped and pollution levels are rising,” said a scientist from Safar, a pollution forecasting agency under the Union government.

Till Saturday, strong winds with a speed of nearly 20km/hour were blowing over the city. Sometimes the wind gusts shot up to 36km per hour clearing the pollutants. According to scientists from the Indian Institute of Tropical Meteorology, a wind speed of 10km/hour is favourable for Delhi.

Ventilation index, which determines how fast pollutants are dispersed, is also very low, scientists said. While a ventilation index of around 6,000 sqm/second helps Delhi get rid of pollutants, the ventilation index has come down to 1,500 sqm/second.

The minimum temperature, recorded just before sunrise on Monday, stood at 10.5 degrees Celsius. It was one degree below normal. The minimum temperature had dropped to 10.4 degrees Celsius on Sunday making it the coldest day of the season so far.

“The night temperature could go up by two to three degrees over the next few days and there may be shallow-to-moderate fog in the morning,” said an official of the India Meteorological Department.