How wind direction helped Delhi air quality remain unaffected by Noida explosion

There was no impact on Delhi’s air quality by the dust generated after the demolition of the Supertech twin towers in Noida on Sunday, with north to northwesterly winds blowing it towards Greater Noida and further towards Uttar Pradesh, instead of making its way across the Delhi border, experts said.

The nearest Delhi Pollution Control Committee (DPCC) air quality monitoring stations at Okhla Phase-2, Dr Karni Singh Shooting Range and Patparganj failed to show any spike in the PM 10 concentration from 3pm onwards and forecast by the India Meteorological Department (IMD) shows wind direction is likely to stay northwesterly in the next 24 hours as well.

Dust, which comprises of coarser particles, is generally known to increase the local PM 10 concentration as opposed to PM 2.5. Dust storms over the past few years have led to Delhi’s AQI reaching ‘very poor’ or ‘severe’ in summer months too, largely on account of high PM 10 levels. However, DPCC readings from Patparganj, the nearest continuous ambient air quality monitoring station (CAAQMS) in east Delhi only showed a minimal increase following the demolition. The hourly PM 10 concentration at the station increased from 130 micrograms per cubic metre at 2pm to a reading of 149 micrograms per cubic metre at 3pm, before dropping back down to 132 micrograms per cubic metre at 4pm.

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Over towards south Delhi, the nearest CAAQMS across the border is Okhla-Phase II, which showed a slight drop in PM 10 from 2pm onwards, indicating there was no impact of the controlled implosion. The PM 10 concentration dipped from a reading of 138 micrograms per cubic metre at 2pm, to a reading of 132 micrograms per cubic metre at 3pm and a further drop down to 118 micrograms per cubic metre at 4pm.

“Wind direction is north to northwesterly and following the explosion, the dust began to gradually blow towards Greater Noida. Wind direction is likely to stay northwesterly till at least Monday afternoon and after that, it may switch to easterly, however, even then, Delhi is unlikely to be impacted by this dust as a change in wind direction generally leads to calm winds,” said Mahesh Palawat, vice president at Skymet meteorology.

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According to IMD, Delhi’s wind direction is likely to stay northwesterly for the majority of the next three days, with it also forecasting light rain in parts of Delhi on Monday. “Wind speed on Sunday was strong, but it was northwesterly and therefore, will not impact Delhi much. Rain is also expected in Delhi on Monday, so any dust in the air even towards Delhi is likely to settle and there will not be any impact of this event,” said a met official.

Delhi’s air quality index (AQI) was, meanwhile, recorded in the ‘moderate’ category on Sunday, with an AQI reading over a 24-hour period recorded at 119 as per Central Pollution Control Board’s daily national bulletin, which is released at 4pm. This was slightly higher than the average 24-hour reading of 105 (moderate) on Saturday.

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According to the ‘Early Warning System For Delhi’ developed by the Ministry of Earth Sciences (MoES), air quality is unlikely to deteriorate over the next few days.

“The air quality over Delhi is likely to remain in the ‘moderate category’ on Sunday and Monday. The air quality is then likely to improve but remain in the ‘moderate’ to ‘satisfactory’ category on Tuesday and will improve to the ‘satisfactory’ category on Wednesday,” the forecast issued by the MoES-developed system states.