Delhiites woke up to a biting cold wave with fog on Monday morning even as parts of the national capital received light showers. The minimum temperature recorded in the city stood at 8.6 degrees Celsius, according to the Safdarjung Observatory, a notch below the seasonal average while the maximum settled at a chilly 20 degrees Celsius. Palam weather station recorded a rainfall of 0.4 mm. Other stations, including Safdarjung, Lodhi Road, Ridge, and Aya Nagar recorded trace amounts of rainfall as of 8.30 am.
However, the light rain failed to improve the Air Quality Index (AQI) in the capital which remained in the 'severe' category for the second straight day at 406 indicating the persistent air pollution issue faced by the capital. The air quality index was in the severe category despite implementation of the stage IV of the Graded Response Action Plan (GRAP) to curb air pollution.
Initially, there was a glimmer of reprieve in the morning when the AQI showed mild improvement, moving to the higher range of the "Very Poor" category. However, this improvement was short-lived, as the air quality worsened to "Severe" again by the afternoon. Typically, rainfall is seen as a natural cleanser of the atmosphere, helping to wash out pollutants and improve air quality. However, Monday's weather conditions were not conducive to this process. The rainfall was too light to have a substantial impact on the entrenched pollutants. One of the contributing factors to this situation was the relatively calm wind speeds that did little to disperse the pollutants.
The air pollution in Delhi was— over 74. 4 times — the limit prescribed by the World Health Organisation (WHO) in the morning. The overall level of PM2.5 (a chief pollutant) in Delhi was 372 micrograms per cubic meter as compared to 311 micrograms per cubic meter on Sunday afternoon.
The overall level of Particulate Matter under 10 microns was 570 as compared to 457 micrograms per cubic meter a day before.
The level of Nitrogen dioxide (NO2) was recorded 69.7 micrograms per cubic meter, as against the World Health Organization’s (WHO) limit being far stricter at 25µg/m3. According to SAFAR-India, Alipur station read an AQI of 437, while Anand Vihar recorded 443, Ashok Vihar 460, Bawana 475, Burari Crossing 445, Dwarka Sector 8 393, IGI Airport 357, ITO 414, Jahangirpuri 453, Jawaharlal Nehru Stadium 405, Mandir Marg 403, Mundka 446, Najafgarh 372, Narela 428, North Campus DU 416, Okhla Phase 2 428, Punjabi Bagh 424, RK Puram 429, Rohini 468, Siri Fort 422, Sonia Vihar 456, Vivek Vihar 438, and Wazirpur 464 among others. Notably, air quality in Dwarka-Sector 8 and Najafgarh hovered just below the ‘severe' threshold.
The Decision Support System (DSS) of the Delhi Air Quality Management has not been updated since December 21.
The ventilation index lower than 6000 m2/s with average wind speed less than 10 kmph is unfavourable for dispersion of pollutants.
However, December 24 and 25 are expected to witness mainly clear skies. On both the days, the IMD predicted smog/moderate fog in most of the places and dense fog in isolated places in the mornings. Smog/shallow fog conditions are expected on both the nights.
