Delhi breathes clean air, rain helps wash away pollutants

New Delhi:

Delhi on Thursday breathed the cleanest air since October 2 as the air quality improved further in the ‘moderate’ category, according to the Central Pollution Control Board’s (CPCB) 4 pm bulletin and further to the ‘satisfactory’ zone by the evening.

While scattered rainfall and gusty winds accompanied with hail in parts in the national capital region washed pollutants away, it resulted in a significant drop in the mercury, making it the coldest day of the season so far.

The city is expected to breathe relatively clean over the next few days owing to the impact of light rain over the past 24 hours. The air quality may, however, dip slightly on November 30, government agencies said.

Scientists at the India Meteorological Department (IMD) said the cumulative effect of rain in NCR helped clean the air. “Even though Delhi received only traces over the past two days, continued rainfall in neighbouring regions such as Haryana, Greater Noida and Ghaziabad did not allow intrusion of pollutants,” a senior IMD scientist said.

The average wind speed was 25-30 kmph, which went up to 35 kmph for a few hours in the day, which helped clean the air, he said.

The air quality index (AQI) was 106, as against 134 the previous day. By 6 pm, the AQI was even better and was recorded in double digits at 90 in the ‘satisfactory’ zone and 83 by 8.30pm. Previously, the AQI was in ‘satisfactory’ zone on October 5, with an AQI reading of 98. On October 2, the AQI was 90.

According to IMD, while Safdarjung Observatory, representative for Delhi’s weather, recorded only ‘traces’ of rain, Delhi Ridge received 3 mm rainfall and Palam got 0.8 mm rain.

Continued rainfall resulted in a sharp drop in the day temperature, recorded at 22 degrees Celsius, four notches below normal --- coldest of the season. On Wednesday, the day temperature was 27.4 degrees C.

“The normal day temperature for this time of the year is around 25 degrees C. It was mainly rain and gusty winds that brought the mercury down,” said Kuldeep Srivastava, head, IMD’s regional weather forecasting centre.

However, the night temperature was 16.2 degrees C, six notches above normal, mainly because of cloud layer. Met officials explained that when there is a layer of clouds at night, the minimum temperature does not fall. However, clouds and rain in the daytime result in a drop in the maximum temperature.

The night temperature, however, is expected to drop to 10 degrees C on December 1.

The System of Air Quality and Weather Forecasting and Research (Safar), ministry of earth science’s weather and air quality monitoring wing, too has forecast that air quality may dip slightly on November 29-30.

“Widespread rain and gusty winds did not allow pollutants to travel to Delhi. The share of crop residue burning in neighbouring states of Punjab and Haryana to overall Delhi pollution was not significant,” said a SAFAR scientist.