Delhi: Dusty winds push air quality into poor zone, rain likely from June 12

India Meteorological Department (IMD) said such dry and dusty conditions are likely to continue on Wednesday and Thursday as well. But some relief is likely from June 12, when a fresh western disturbance is expected to trigger rain in the city.

After experiencing a long spell of good air days, courtesy the Covid-19 lockdown, the effects of two cyclones and numerous western disturbances, Delhi’s air quality slipped into the ”poor” category on air quality index (AQI) on Tuesday with dust carrying south-westerly winds sweeping across the city at speeds ranging from 30-40 kmph.

As dusty winds continued to impact Delhi’s air quality throughout Tuesday, the average reading of PM10 was 244.2ug/m3 at 4pm, as compared to 160ug/m3 on Monday evening.

India Meteorological Department (IMD) said such dry and dusty conditions are likely to continue on Wednesday and Thursday as well. But some relief is likely from June 12, when a fresh western disturbance is expected to trigger rain in the city.

According to the Central Pollution Control Board (CPCB), the overall air quality in Delhi on the AQI scale was 205 or ”poor”, a step-up from Monday’s AQI of 180 or “moderate”. On a scale of 0 to 500, a reading between 100-200 is considered moderate, while that between 200 and 300 is considered poor.

A senior IMD official said dry and dusty conditions are expected to prevail over the entire north-west India till June 10. “Winds carrying dust from the Thar Desert are blowing over Delhi, Haryana and parts of Uttar Pradesh. Through satellite images, we can see a layer of dust hanging low over the region. Similar conditions are expected till June 10, which means that pollution levels, especially the levels of PM10 (particulate matter with a diameter less than 10 micrometres), are likely to deteriorate further in the next two days,” the official said, asking not to be named.

As dusty winds continued to impact Delhi’s air quality throughout Tuesday, the average reading of PM10 was 244.2ug/m3 at 4pm, as compared to 160ug/m3 on Monday evening. Localised recordings from Delhi localities also showed that the predominant pollutant in most areas was PM10.

CPCB’s hourly average recordings show that around 7pm, the pollution levels at two monitoring stations -- Chandni Chowk and ITO -- had already touched the “very poor” zone (a reading between 300 and 400 on AQI scale), with the PM10 readings breaching the 300ug/m3 mark, as against the national permissible limit of 100ug/m3.

Delhi experienced a long spell of good air, thanks to the Covid-19 lockdown, the impact of two major cyclonic storms and the higher than normal western disturbances. CPCB data shows that before Tuesday, Delhi witnessed ”poor” air quality on May 23, when the average AQI had dipped to 237.

IMD forecast also said after a spell of dry and dusty weather, Delhi is likely to receive another bout of rain from June 12 under the impact of a western disturbance. “On June 12, we might receive light rain in isolated pockets, but on June 13 most parts of the city are expected to get rain,” the IMD forecasters said.

Delhi on Tuesday recorded a maximum temperature of 41.7 degrees Celsius at the Safdarjung observatory, which is considered the official marker for the city. The minimum temperature was 28.6 degrees Celsius.

“We have a forecast of the temperatures rising further tomorrow (Wednesday) and reaching around 42 degrees Celsius. But after June 12, the temperature will start dropping and we are expecting it to go below 40 degrees Celsius,” said Kuldeep Srivastava, head of IMD’s regional weather forecasting centre.

Despite the high-temperature forecast, Met officials said Delhi is unlikely to record a heatwave this season. In the plains, heatwave days are recorded when two things happen – when the maximum temperature crosses 40 degrees Celsius, and when the day temperature exceeds the region’s normal maximum temperature by 4.5 degrees Celsius. A severe heatwave is declared when there is a departure of 6.5 degrees Celsius or above from normal temperatures.