From 78 to over 200: Why did Delhi's air become unbreathable again?

Delhi's air quality deteriorated yet again on Saturday, with the city's Air Quality Index (AQI) climbing from around 78 to 222 in 24 hours, according to AQI.in data at 11:31 am on October 31.The rise comes after a brief improvement following rainfall and stronger winds earlier in the week that cleared the air and dropped pollution levels across the capital. Haze is seen over the Yamuna river, in New Delhi. (Photo: PTI) The latest readings show pollution building up again, despite rain across most parts of the capital over the past 24 hours.Data from AQI.in showed pollution levels climbing steadily through Saturday afternoon and evening, reaching their highest levels around midnight before easing during the early morning hours. However, the improvement did not last as the index began rising again on Saturday morning, crossing 220 by 11:31 am. A graph illustrating Delhi's AQI in the last 24 hours. (Photo: AQI.in) RAIN AND WINDS BROUGHT ONLY TEMPORARY RELIEFThe India Meteorological Department's (IMD) latest weather bulletin provides some clues about the changing conditions. Delhi received very light to light rainfall at most places during the preceding 24 hours. Safdarjung, the city's primary weather station, recorded 4.2 mm of rain, while other areas, including Lodi Road and Ayanagar, also received rainfall.Winds were southwesterly, reaching speeds of 15-25 kmph and gusting up to 35 kmph during the day.Such conditions can help disperse pollutants, while rainfall can wash some pollution particles out of the air. Commuters walk past amid low visibility due to a thick layer of smog. (Photo: PTI) However, wind speeds had eased considerably by Saturday morning. The IMD recorded southwesterly winds at just 6 kmph at 8:30 am.The change in wind conditions may have contributed to the renewed pollution build-up, although weather is not the only factor. Vehicle emissions, construction dust, industrial pollution and other sources continue to add pollutants to the air.CLEAR SKIES, WARMER DAYS AHEADThe weather outlook offers little prospect of another respite as a spell of rain is largely unexpected.The IMD has forecast mainly clear skies over Delhi for the coming days, with no rainfall expected until at least November 6. A satellite image shows the weather systems over the Indian subcontinent. (Photo: IMD) Northwesterly winds are likely to reach 15-25 kmph during the afternoon on November 1, before generally remaining between 15 and 20 kmph over the following days.Maximum temperatures are also expected to rise by 3-5°C over the next five days. Delhi's maximum temperature at Safdarjung was 20.7°C on Friday, 10.3 degrees below normal.While stronger afternoon winds could help disperse some pollutants, the absence of rain means the city will have to contend with its existing pollution sources.Whether air quality improves will depend on how these emissions interact with changing wind and weather conditions.- Ends