By Aakanksha Khajuria New Delhi, Oct 23 : Nine of the 36 pollution monitoring station in Delhi showed 'severe' air quality index on Friday, according to the Central Pollution Control Board's data. According to the pollution monitoring agency, AQI in North Delhi's Alipur area was 447, which falls in the 'severe' category, followed by Shadipur, Wazirpur, Jahagirpuri, Mundka, Patparganj, Anand Vihar, Bawana, and Vivek Vihar. Besides these, 26 pollution monitoring station showed 'very poor' reading and one logged moderate air quality index. The overall pollution levels continued to be in the lower end of the 'very poor' category at 372 at noon. Vijay Kumar Sonu, Head of Environment Monitoring and Research Centre at IMD told IANS that "due to calm wind there is no dispersion of pollutants". "The wind speed will, however, pick up from October 26 and would likely result in improvement of AQI," he said. The System of Air Quality and Weather Forecasting and Research, which comes under the aegis of Ministry of Earth Sciences, also stated that the most dominant factor for deterioration is extremely calm surface wind in Delhi, combined with low inversion height followed by moderate stubble related intrusion. "Highly calm surface wind conditions prevail over the Delhi region and is forecast to continue for next two days. It will lead to low ventilation conditions and little dispersion for an extended period and hence accumulation of pollutants near the surface. Further deterioration of AQI is predicted for the next 2 days," the forecasting agency added. SAFAR also stated that there was significant stubble fire count around Haryana, Punjab, and neighbouring regions with the counts at 1,213 on Thursday, slightly less than what was a day before. "However, the boundary layer wind direction is not fully favourable for pollutant transport towards Delhi region, the SAFAR model estimate of stubble burning share in PM2.5 is 17 per cent for today," it added. Neighbouring Gurugram, Ghaziabad, Faridabad, Noida and Greater Noida -- also recorded 'very poor' quality of air. Greater Noida and Noida air is currently the most polluted among all. Nationwide, as many as 18 cities have very poor quality of air. Greater Noida tops the charts at 392, followed by Uttar Pradesh's Baghpat, Noida and Panipat. Shillong recorded the cleanest air in the country. (Aakanksha Khajuria can be contacted at aakanksha.k@ians.in) /IANS