Air quality may dip this week, foggy mornings to return

An anti-cyclonic circulation is likely to form from Wednesday night and south-easterly winds are likely to gush in which will lead to drop in wind speed, said a Met official

The Capital’s air quality, which was ‘very poor’ on Sunday, may deteriorate from Wednesday for a brief period, scientists from the Central Pollution Control Board (CPCB) said.

On Sunday, the minimum temperature was 5.7 degrees Celsius while the maximum temperature hovered around 25 degrees Celsius. (Sushil Kumar/HT Photo)

On Sunday the Air Quality Index (AQI) of Delhi was 358 just one notch higher than Saturday’s 357. An AQI value between 300 and 400 on a scale of 0 – 500 is considered as ‘very poor’.

“An anti-cyclonic circulation is likely to form from Wednesday night. South-easterly winds are likely to gush in. As a result, wind speed would drop and moisture levels would shoot up,” said a senior official of the regional weather forecasting centre.

Over the past two days, Delhi benefitted from strong winds blowing at 15 km /hour. Winds help flush out the pollutants and the air quality improved from ‘very poor’ category to ‘poor’ category on Friday.

“Low wind speed and increasing moisture levels could result in a spike in pollution. While moisture trap the pollutants, the low velocity wind is not able to flush them out. As a result, pollutants accumulate,” said D Saha, head of the air quality laboratory at CPCB.

Temperature

Met officials have forecast that there won’t be any drastic change in temperature. On Monday morning, minimum temperature in was recorded at 6 degree Celsius with the maximum at 25 degree Celsius. India Meteorological Department has predicted moderate fog during the day.

New Agency ANI reported that a total of 39 trains, arriving in Delhi, were delayed, while four were rescheduled and 13 got cancelled. According to Delhi airport website, six flights were delayed on Monday.

On Sunday, the minimum temperature was 5.7 degrees Celsius, two degrees below the climatic normal. With a clear sky and lot of sunshine, the maximum temperature hovered around 25 degrees Celsius, which was five degrees higher than usual this time of the year.

Low wind speed and moisture could trigger foggy mornings and low visibility.

“Even though at present we are witnessing some shallow fog in the morning hours with visibility around 700-800m, there could be some moderate fog on Thursday because of these changes in the weather parameters. Visibility could drop to less than 500m,” Saha added.

A senior MeT official said that this, however, won’t affect flight schedules.“The anti-cyclonic circulation won’t last more than a day or two. We expect the winds to pick speed from Friday again,” said the Met official.