Rainfall pushes up temperature, Delhi's air quality improves

6 months ago 26
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Two back-to-back days of rainfall in Delhi pushed the temperature up on Monday, giving relief from the biting cold in the city over the past few weeks, and sent pollution levels down, giving residents the cleanest air in 38 days.

The minimum temperature lodged on Monday at Safdarjung Observatory, which is considered representative for Delhi, was 11.4 degrees Celsius, four notches above normal and the highest in the last 22 days, according to Indian Meteorological Department (IMD). The maximum temperature was 22.6 degrees Celsius, three notches above normal.

Weather scientists said the cloud cover in city helped bring the temperature up as clouds trap some of the outgoing infrared radiation and radiate it back downward, warming the ground. The inclement weather in the city is likely to persist till Wednesday, with moderate rains and thunderstorm likely on Tuesday as well, IMD scientists said.

“There was a hailstorm in neighbouring areas of Delhi as per our radar images. Similar weather will continue on Tuesday,” said Kuldeep Shrivastava, head, regional weather forecasting system.

On Monday, Delhi recorded an air quality index (AQI) of 151, placing it in “moderate” category — a substantial improvement compared to the past three days. On January 1, Delhi’s AQI was in 441, placing it in the “severe” zone; while it was 443 on January 2, also in “severe” category; and it was 354 on January 3 in “very poor” category.

Read more| 40mm rain in 36 hrs throws Delhi out of gear, more likely today: IMD

This was the first time since December 14, 2020, that the air in the city was in the “moderate” category (AQI of 160) and the cleanest air that Delhi has breathed since November 27, when the AQI touched 137.

Dense fog enveloped the city in the morning, with the visibility dropping to around 50 metres at Safdarjung.

Officials at Delhi’s Indira Gandhi International Airport, however, said that the morning fog had no impact on flight operations on Monday. As many as 14 flights scheduled to depart from Delhi for Srinagar were cancelled due of poor weather conditions in Srinagar, while four flights scheduled to arrive at Delhi from Srinagar had to be cancelled as the flights could not take off from Srinagar, the official added.

Experts said that the rain and strong winds through Monday played a crucial role in bringing the pollution down.

“The pollution has been washed away after intense rain on Sunday. Strong winds today blowing at 15 to 20 kmph hasn’t allowed accumulation of pollutants. We are expecting air quality to remain in ‘moderate’ to ‘poor’ category till January 9. This is because wind speed is likely to remain moderate, which will help disperse pollutants continuously,” said VK Soni, scientist at IMD’s air quality division.

Several parts of north India witnessed light to moderate rains due to a western disturbance and above-normal temperatures on Monday, the IMD said. Several parts of northwest India are continuing to receive widespread and heavy rain with thunderstorms and lightning. There is likely to be hailstorms at many places on Tuesday, IMD said.

“There is western disturbance as a cyclonic circulation over central Pakistan. There is a lot of moisture incursion due to southesterlies and a confluence or interaction of southwesterly and southeasterly winds is causing extreme weather. There is also an induced cyclonic circulation over Rajasthan. Our radar images are showing a lot of rain and thunderstorm over Punjab, Jammu and Kashmir, east Rajasthan and Haryana. There may have been hailstorm also. Similar weather will persist tomorrow (Tuesday) but the spatial distribution and intensity may reduce from Wednesday,” said K Sathi Devi, head, national weather forecasting centre.

“The next western disturbance, which is likely to approach the region around January 7, will not bring much rain to the plains because it’s a feeble system. Its impact will be limited to the hills,” Shrivastava said.

An active western disturbance lies as a middle and upper-level cyclonic circulation over Central Pakistan with its induced cyclonic circulation over southwest Rajasthan and neighbourhood. A north-south zone of wind confluence continues to exist from north Punjab to northeast Arabian Sea, with strong interaction between south westerly winds and and lower level moist southeasterlies. All these meteorological features favourable for rain are likely to persist over the next three days, according to the IMD bulletin on Monday.

Hailstorm in isolated places is likely over Jammu and Kashmir, Ladakh, Gilgit-Baltistan and Muzaffarabad, Himachal Pradesh, Uttarakhand, Punjab, Haryana, Chandigarh and Delhi on January 4 and 5 and over west Uttar Pradesh on January 5. Heavy rain or snowfall is also likely over Jammu & Kashmir, Ladakh, Gilgit-Baltistan & Muzaffarabad on January 4 and 5; over Himachal Pradesh and Uttarakhand on January 5 and isolated heavy rainfall over northern parts of Punjab on January 4 and 5.

A fresh western disturbance is likely to affect western Himalayan Region from January 7. As a result, no significant change in minimum temperatures is likely during the next 2-3 days over northwest India, the bulletin said.

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