The Indian Institute of Tropical Meteorology (IITM) from Sunday resumed sharing data on the sources of pollution contributing to Delhi’s PM2.5 levels through its Decision Support System (DSS), days after the institute initially limited access to the portal.
Meanwhile, Delhi’s air quality deteriorated further on Sunday, with DSS data showing that the city’s transport sector and neighbouring cities in the National Capital Region (NCR) added more pollution to the Capital’s air than smoke from stubble burning did.
To be sure, stubble burning is yet to pick up in the upwind agrarian states, especially Punjab.
Delhi’s air quality index (AQI) worsened to 325 on Sunday, from 303 a day ago, both in the “very poor” category, showed data from the Central Pollution Control Board (CPCB). Sunday’s AQI is the worst so far this season.
Data from DSS will help authorities tailor responses to the city’s spiking levels, said experts.
The two models — System of Air Quality and Weather Forecasting And Research (Safar) and DSS — had temporarily stopped sharing data on air pollution for the country as there were differences between their forecasts and source contribution, IITM had said. However, after criticism from experts that the lack of information was hampering Delhi’s attempts to tackle air pollution at a crucial time, IITM resumed sharing data on the sources of pollution.
Forecasts by its forecasting model, Early Warning System (EWS) for Delhi, said Delhi’s air is likely to remain in “very poor” till November 1, but not touch ‘severe’.
The DSS, which had last shared pollution data on Tuesday, before going behind a lock and requiring a login, said Delhi’s transport sector contributed around 18.48% to Delhi’s PM 2.5 concentration on Sunday, followed by the neighbouring NCR towns of Gautam Buddha Nagar (7.22%) and Gurugram (6.79%). The contribution of stubble burning was 6.7% on the day — despite a rise in farm fires across the northern plains — with Delhi largely being helped by a change in wind direction over the last 48 hours. DSS also said around 20.2% of pollution was coming from unaccounted sources or the “others” category.
It predicted a marginal rise in stubble burning to 11.18% on Monday, and is expected to be at around 9.44% on Tuesday. This will still not be Delhi’s lead contributor, with the transport sector’s contribution to hover around 11.5% over the next two days, while the contribution from Gautam Buddha Nagar could rise to 14.91% on Monday and be around 13.81% on Tuesday.
An IMD official said even though a change in wind direction from northwesterly to southeasterly had reduced the impact of stubble burning, wind speeds too had dropped in the region, therefore allowing pollutants to accumulate. “Wind direction changed to southeasterly from Saturday and winds have been calm at night and slow even during the day. We expect wind direction to remain southeasterly till November 1,” said IMD scientist Kuldeep Srivastava.
On Sunday, Punjab recorded its highest single-day farm fire count of the season. Data from the Indian Agricultural Research Institute (IARI) showed the northern state recorded 1,068 fires. Its previous highest single-day count this season was 766 on October 27. Haryana, meanwhile, recorded 75 fires on the day. Its highest single-day count this season so far came on October 15 (127 fires).
DSS had halted stubble burning contribution data on October 13, before last issuing an update on October 22. On October 24, DSS was put behind a lock, with the website then requiring a login. On October 27, IITM had clarified that “there were differences between the forecasts and source contribution being issued by their two models”, adding this was particularly true when it came to stubble burning contribution.
An IITM official on Sunday said these differences had been rectified, with data to be shared only from one source now, moving ahead, which will be DSS. “The site was restricted for registered use for a brief while to synchronise the information and data of Safar and DSS. Now, data will be available through DSS once more, and it will be the only source that will be used and not Safar,” the official said.
Forecast by the Early Warning System (EWS), which comes under the ministry of earth sciences and is also executed by IITM, showed ‘severe’ air was unlikely in the coming days.
“Delhi’s air quality is likely to be in the ‘very poor’ category from Monday till Wednesday. The outlook for the subsequent six days shows air quality is likely to be between the ‘very poor’ and ‘poor’ category,” said EWS on Sunday.
An AQI of 51 to 100 is classified as ‘satisfactory’, between 101 and 200 is classified as ‘moderate’, between 201 and 300 is classified as ‘poor’, between 301 and 400 is classified as ‘very poor’ and over 400 is ‘severe’ as per the CPCB.
The change in wind direction also led to a slight rise in temperature across the capital. Delhi’s minimum temperature, which was recorded at 14.3 degrees Celsius on Saturday, rose by two degrees to 16.3 on Sunday and that is around the normal mark. Delhi’s maximum was recorded at 33.4 degrees Celsius, two degrees above normal. It was 32.5 degrees on Saturday.
“The change in wind direction has meant the impact of cold northwesterly winds has gone down. The minimum will be around 16 degrees over the next two days and the maximum should hover around 32 degrees,” Srivastava added.