How change in wind direction helped improve Delhi’s AQI, marginally

As per data recorded by the Delhi Pollution Control Committee’s AQI monitors and the India Meteorological Department (IMD), the concentration of particulate matter improved significantly during the day and with the wind changing direction from north to northeast. A temperature of 32.1 degrees Celsius, normal for this time of the year, and clear skies also lent a helping hand.

Air quality improved even as the number of farm fires in Punjab rose from 152 on Monday to 360 on Tuesday, and from 29 to 70 in Haryana, according to the Indian Agricultural Research Institute (IARI) monitoring data.

The predominant direction of winds in Delhi is northwesterly post-monsoon. These winds bring dust and smoke to the city when stubble is being burnt in Haryana and Punjab. A change in wind direction means these pollutants are not carried into the city. A dip in temperature also means that pollutants accumulate in the air easily. Several monitoring stations in the city saw the concentration of PM 2.5 and PM 10 dip to below acceptable limits for several hours.

At India Gate, for example, the PM 2.5 concentration was 35 microgrammes per cubic metre at 5 pm against acceptable limits of 60 microgrammes per cubic metre. In the evening, however, as Dussehra celebrations started across the city, the AQI started dipping, with the same location recording a PM 2.5 concentration of 114 microgrammes per cubic metre.

Similar spikes were seen across several parts of the city.

At Jawaharlal Nehru Stadium, the PM 2.5 concentration increased from 28 to 66 microgrammes per cubic metre between 5 pm and 8 pm. At Dwarka, the increase was from 35 to 114 microgrammes per cubic metre.

According to the IMD forecast, the wind direction is expected to shift between north and south easterly and northwesterly starting Thursday, which could prove helpful to Delhi.