Delhi's Air Quality Inches To Severe For The First Time This Season, Spike In Farm Fires To Blame
As the number of farm fires burning in Punjab has gone up, it has added to the woes of Delhiites who have been breathing toxic air for the past couple of weeks.
On Thursday, the national capital's overall air quality inched closer to the ¡°severe¡± category for the first time this season.
Delhi recorded an air quality index (AQI) of 397 at 11:00 am on Thursday. The 24-hour average AQI was 297 on Wednesday, 312 on Tuesday, 353 on Monday, 349 on Sunday, 345 on Saturday and 366 on Friday.
An AQI between 0 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'.
The air quality dropped significantly on Thursday after a marginal reduction the previous day.
According to the authorities, the primary reason for the drop is winds and a spike in farm fires.
The central government's Air Quality Early Warning System for Delhi said a significant increase in the number of ¡°fire points¡± was observed over Punjab (around 3,000), Haryana and Uttar Pradesh, on Wednesday, which is likely to impact the air quality of Delhi-NCR and other parts of northwest India.
NASA's satellite imagery showed a large, dense cluster of fires that covered most parts of Punjab and some regions of Haryana.
According to the Ministry of Earth Sciences' air quality monitor, SAFAR, the share of stubble burning in Delhi's PM2.5 concentration was 36 per cent on Thursday, the maximum so far this season, double of the 18 per cent on Wednesday.
It was 23 per cent on Tuesday, 16 per cent on Monday, 19 per cent on Sunday and 9 per cent on Saturday.
SAFAR said accumulation of locally generated pollutants and increased external intrusion due to north-north westerly boundary level winds from regions where stubble is burnt, will be major factors for the increase in PM2.5 levels.
"Extremely calm surface and boundary layer winds along with the low nighttime boundary layer height resulted in low ventilation...practically stagnant, no dispersion condition has resulted in the current situation,¡± SAFAR said.
A senior scientist at the India Meteorological Department (IMD) said the wind speed dipped on Wednesday which allowed accumulation of pollutants.
According to IMD, the predominant wind direction was northerly and the maximum wind speed was 8 kilometers per hour. The minimum temperature was recorded at 12.5 degrees Celsius - the lowest in this season so far.
Calm winds and low temperatures trap pollutants close to the ground, while favorable wind speed helps in their dispersion.
