Delhi breathes three consecutive days of satisfactory air for the first time this year

The national capital breathed three consecutive days of “satisfactory” air for the first time this year, from March 5 to March 7, according to data from the national

The national capital breathed three consecutive days of “satisfactory” air for the first time this year, from March 5 to March 7, according to data from the national anti-pollution body. It is also the first time that March has seen “satisfactory” (till Monday) air since the Central Pollution Control Board (CPCB) starting making air quality data public, in May 2015.

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Satisfactory air, according to the CPCB’s air quality index (AQI), will have a value from 51 to 100 and will cause “minor breathing discomfort to sensitive people”. It is the second-best category of air quality, the first being “good” with an AQI of 0 to 50.

Air quality in the city has ranged between “moderate (AQI value 101 to 200)” and “satisfactory” over the past nine days, owing to frequent spells of rain and strong surface winds that helped cleanse the air of particulate matter, government agencies said.

Delhi received over 30mm of rain over 48 hours, between March 5 and 6.

On Monday, as per the CPCB’s daily 4pm bulletin, the 24-hour average AQI was 123, in the “moderate” category. It was 164 on Sunday, also in the “moderate” zone.

The city saw light rain on March 1, and the AQI was recorded at 90 (“satisfactory”), after which it fell to “poor” for two days. It again improved from March 4, after another spell of light rain and thunder.

According to CPCB officials, the frequent spells of rain this month have helped wash away pollutants. “This is the first time since 2017 that the first nine days of March have had three ‘satisfactory’ air days. Usually air quality in March fluctuates between poor and moderate, as wind speed is good during this time. This year, however, a good spell of rain helped keep the air quality in check at a stretch,” said VK Shukla, head of CPCB’s air quality laboratory.

Scientists at the India Meteorological Department (IMD) attributed the clean air spell to the frequent western disturbances (WDs) that have hit Delhi this year. “It is not even mid-March and two WDs have already hit Delhi, while a third one is expected to approach from Tuesday night and result in rainfall and gusty winds on March 12-13. Last year during this time, winds were good, but it did not rain as much. This time, the rains have been widespread, across all of northwestern India, which helped cleanse the atmosphere of pollutants for a long time,” said Kuldeep Srivastava, head, IMD’s regional weather forecasting centre.

Air quality is likely to remain between the moderate and satisfactory categories for the remainder of this week. On March 13, good rainfall and gusty winds up of 30-35kmph are likely. The wind speed started picking pace from Monday itself when the average speed was 20kmph, favourable for the dispersal of pollutants, he added.

The rain and winds also brought the mercury down. On Monday the maximum (day) temperature was 25.2 degrees Celsius, three notches below normal while the minimum (night) settled at 12.4 degrees Celsius, two notches below normal.

“The temperatures are likely to remain below the average till at least March 15 due to expected rain and thunder,” Srivastava added.