Delhi logs cleanest Feb in 9 years, coldest since 2008 | Latest News Delhi - Hindustan Times

Delhi logs cleanest Feb in 9 years, coldest since 2008

Feb 29, 2024 05:58 AM IST

Strong surface winds and rain, both help settle or disperse pollutants in the atmosphere, leading to cleaner air

The Capital has recorded its cleanest February in nine years — owing to strong surface winds cruising through the city combined with intermittent spells of rain — according to data from the Central Pollution Control Board.

At Central Park in Connaught Place on Wednesday. (Sanjeev Verma/HT Photo)
At Central Park in Connaught Place on Wednesday. (Sanjeev Verma/HT Photo)

For the majority of the month, northwesterly winds blowing through the Capital curtailed the average monthly minimum temperature from rising and capped it at 9.2 degrees Celsius (°C) — the lowest for Delhi since February 2008, when it was 8.4°C, the India Meteorological Department (IMD) said.

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The average air quality index for February settled at a reading of 220 (poor) — data accounted for till February 28 showed — since AQI was launched in April 2015. The monthly average minimum temperature was 1.4°C below the long-period average (LPA) of the month.

Meanwhile, the average monthly maximum temperature was recorded at 24°C — 0.2°C below the LPA and Delhi’s lowest for the month since 2019 (22.5°C).

Weather officials said that four western disturbances were recorded this month, with a majority of the rainfall — 26.5mm — on the first day of the month. February so far has recorded 32.5mm, which is the highest for the month since 48.8mm in February 2014.

“We had four western disturbances, but only the first one was active, which impacted Delhi on January 31 and February 1. The second impacted between February 4 and 5, the third around February 20 and the latest on February 27. The last three were fairly weak and only brought a drizzle, but kept wind speed high, particularly during the day,” said Kuldeep Srivastava, scientist at IMD

Strong surface winds and rain, both help settle or disperse pollutants in the atmosphere, leading to cleaner air. CPCB data showed the average AQI for Delhi in February has been 237 in 2023; 225 in 2022; 288 in 2021; 241 in 2020; 242 in 2019; 243 in 2018; 267 in 2017 and 293 in 2016. AQI between 201 and 300 is categorised as poor. The 301-400 range is considered very poor and 401-500 severe. The AQI above 500 falls under the severe plus category.

Srivastava also said the spell between February 7 and 18 was largely characterised by clear skies — a factor that makes day-time temperatures high and the nights cold. “During this period, we had warm days and cold nights, as there were hardly any clouds to trap heat at night. We also had colder northwesterly winds blowing at that time,” he said.

During these spells, Delhi’s minimum temperature dropped to a low of 5.2°C on February 10, which was five degrees below normal and the lowest February minimum since it was 4.6°C on February 10, 2014. Delhi also recorded another spell of cold nights between February 22 and 26, when the minimum dipped to 7.6°C on February 24.

Mahesh Palawat, vice president at Skymet said despite active western disturbances, Delhi primarily saw rain in the first week of the month. For the remainder of the month, Delhi was largely influenced by strong winds. “We saw large parts of northwest India receive snowfall and rain in February. After fresh snow, cold northwesterly winds often lead to a drop in minimum temperature. Delhi also had clear skies for large chunks of the month, including between February 22 and 26, which led to a late dip in minimum temperature,” he said.

Dipankar Saha, former head of CPCB’s air laboratory said Delhi’s air depended on meteorological conditions once again this winter. “In the absence of strong winds in November, December and even January, we had relatively poor air. That changed in February and accordingly, the average AQI has been lower,” he said, adding that NCR needed to put in greater efforts to reduce background emissions.

The average AQI in January was 354 – the highest since January 2016, when it was 370. In December, the average AQI was 348 – Delhi’s highest since December 2018 (360) and in November, it was 373, Delhi’s highest since November 2021 (376).

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