Dust carrying winds push AQI to very poor, minimum temp highest this year
High-velocity winds, carrying dust from the deserts of Rajasthan, continued to blow over Delhi on Wednesday, pushing the air quality in the national capital into the “very poor” category for the first time since this February. The layer of dust over Delhi-NCR also kept the night temperature from falling, with the result that Wednesday recorded a minimum temperature of 31.4 degrees Celsius, the highest so far this year, the India Meteorological Department (IMD) said.
Central Pollution Control Board (CPCB) recordings show that on Wednesday, the overall air quality index (AQI) in Delhi was 305, categorised as ”very poor” on the AQI scale. On Tuesday, the average AQI was 205, in the “poor” category. On the AQI scale of 0 to 500, a reading between 200-300 is rated as “poor”, while that between 300-400 is classified as “very poor”.
IMD scientists said dusty south-westerly winds have been blowing through the national capital since Tuesday, spiking pollution levels. Pollution recordings confirmed that PM10 (coarse particulate matter with a diameter less than 10 micrometres) was the primary pollutant in Wednesday’s foul air.
At 5pm Wednesday, the PM10 level peaked at 384ug/m3, over three times higher than the acceptable standard of 100ug/m3 in India.
Experts said now that Delhi is on its way to unlocking the economy, focus should be on managing pollution sources to prevent such spikes.
Tanushree Ganguly, programme lead, Council on Energy, Environment and Water (CEEW) said, “Cities across the country need to tackle dispersed sources of pollution such as open burning of waste, dust from construction sites and unpaved roads. Pollution control boards and urban local bodies should have dedicated field inspection teams to identify such sources and ensure that they are addressed. Secondly, we need robust citizen grievance redressal mechanisms. The Green Delhi app is a great move but citizens should be encouraged to use it more actively.”
Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said, “Post-noon on Wednesday, the dust film over Delhi cleared up a bit, but since pollution observatories take a 24-hour average of pollutants, an improvement will be visible on the charts only on Thursday.”
Srivastava also pointed out that this layer of dust as well as clouds were keeping the minimum temperature higher than normal.
The Safdarjung weather station, which is considered the official marker for the entire city, recorded a minimum temperature of 31.4 degrees Celsius on Wednesday, which was four degrees above what is considered normal for this time of the year. The maximum temperature was 42.2 degrees Celsius, three degrees above normal.
“The layer of dust and the clouds trapped the heat from the surface and did not allow the ground to cool off. This kept the minimum temperature high. Wednesday’s is the highest minimum temperature that Delhi has recorded this year,” Srivastava said.
The IMD forecast, however, said that Delhi will get rain from June 12, bringing some relief from the simmering heat. Under the impact of a low-pressure system, which is forming north of the Bay of Bengal, the wind direction over Delhi will change to easterly from late Friday night, which will result in light rainfall in parts of Delhi and NCR.
From Sunday, the intensity of rainfall will increase and, as a result, the temperature will also fall to below 40 degrees Celsius.
“We are expecting moderate rainfall across Delhi while parts of NCR may receive heavy showers. From June 12, the temperature will start decreasing again,” a senior IMD official confirmed.