New Delhi, Nov 10 (IANS): Smog covering the national capital over the last few days was just the start. Scientists say the city is expected to witness a more severe pollution after Diwali Nov 13 with likelihood of western disturbance coinciding with smoke caused by firecrackers.

Scientists at the India Meteorological Department (IMD) running the SAFAR (System of Air Quality Forecasting and Research) -- India's first air quality prediction system -- found that there is likelihood of westerly disturbance from Nov 12-13.

"The western disturbance will lead to further reduction of temperature in the capital. Hence, what is really alarming is that if westerly disturbance coincides with pollution due to Diwali, we may see pollution more severe than last week's," said Gufran Beig, SAFAR programme director at Indian Institute of Tropical Meteorology in Pune.

Delhi was under the grip of smog for almost two weeks (Oct 27-Nov 8) which elevated the level of fine particulate matters (PM2.5 and PM10) to a dangerously high level, affecting people with asthma and other breathing disorders.

"The air quality index (AQI), which crossed a critical (very unhealthy) level of 500 and peaked Nov 7 to 920, has suddenly dropped to around 350 (very poor level) Nov 9," said Sunil Peshin, head of IMD's Environmental Monitoring Research Centre.

According to Peshin, the smog was caused by long range transport of pollution caused by burning of crop residue in Punjab and Haryana.

"Delhi cannot afford to have two extreme pollution episodes back-to-back. If we wish to avoid another such episode, we should minimise use of firecrackers that give rise to huge smoke," said Beig.