Noida: After a week of clear skies and rain that kept pollution levels in check, air quality in Noida, Greater Noida, and Ghaziabad worsened sharply over the weekend as temperatures dipped, trapping pollutants close to the ground. A smog layer lingered over Noida's skyline well into the afternoon -- possibly the first this season. Reduced wind speed, coupled with ongoing construction emissions, also added to the pollutants, with air quality slipping from the moderate to the poor category across the region.According to the Central Pollution Control Board's (CPCB) 4pm readings on Saturday, Noida's Air Quality Index (AQI) rose to 225 from 188 a day earlier, while Ghaziabad recorded 242, up from 176 on Thursday. Greater Noida, where the AQI had already fallen to 203 on Friday, saw a further deterioration to 280. In Delhi, air quality hovered on the edge of the poor range at 199, a steep rise from Friday's 170.In Noida, Sector 125 reported the highest AQI at 316 -- classified as very poor -- while Sector 116 and Sector 1 recorded 221 and 218 respectively, both in the poor range. Sector 62, however, remained moderate with an AQI of 149. Greater Noida's Knowledge Park 3 station logged 295, and Knowledge Park 5, which covers the city's western sectors, recorded 268 -- both in the poor category. Ghaziabad followed a similar pattern. Loni topped the list at 341 (very poor), while Vasundhara, Sanjay Nagar, and Indirapuram registered 238, 235, and 213 respectively, all under poor range.An analysis of CPCB data shows that during the first 10 days of Oct, Noida's air quality largely remained between satisfactory and moderate, dipping to poor only once -- on Oct 1. Greater Noida recorded one 'poor' day in the same period, while Ghaziabad recorded none. Last year, however, Noida saw two poor days, Greater Noida one, and Ghaziabad three during the same stretch.Experts said changing weather conditions have worsened the situation. The Indian Institute of Tropical Meteorology (IITM) reported clear skies on Saturday with northwesterly winds blowing at 10-15 kmph in the afternoon but dropping below 8 kmph by nightfall -- limiting pollutant dispersion.The maximum temperature settled at 29.9°C, four degrees below normal. The minimum was 20°C.After the decline in the region's air quality, the Commission for Air Quality Management (CAQM) held a review meeting on Saturday. Sources said the CAQM decided not to impose stage I of the Graded Response Action Plan (GRAP) as the AQI didn't turn poor on Saturday. The commission will again review the air quality conditions on Sunday. Last week, it had directed NCR states to keep a check on stubble burning.On Saturday, satellites detected 64 farm fires in six states. Of these, 42 were in UP, 14 in Punjab, six in MP, and one each in Haryana and Rajasthan, according to the satellite data compiled by Indian Agricultural Research Institute. Though stubble burning has started in north India, the contribution of paddy residue burning to Delhi-NCR's air quality has remained negligible.According to the Decision Support System (DSS), which estimates the contribution of local and regional sources of pollution in the region's PM2.5, the share of farm fires in Delhi's air was just 0.34% on Friday.DSS estimated that the highest contributor on Saturday was Delhi's transport sector (19.1%), followed by 10.8% of emissions coming from Sonipat and 4.8% of emissions each from Jhajjar and Delhi residential respectively. residential.The Air Quality Early Warning System for Delhi (EWS), under the Union Ministry of Earth Sciences, has forecast that the city's air quality is likely to remain in the 'poor' category till Tuesady.Experts have urged authorities to intensify emission-control measures. Anumita Roychowdhury of the Centre for Science and Environment said stronger, source-specific preventive action is needed ahead of the pollution season. Former CPCB scientist Dipankar Saha added that weakening meteorological conditions after the monsoon trap emissions near the ground, worsening air across the Indo-Gangetic plains.