Minimum mercury in Delhi may dip to 6°C this weekend: IMD
According to the Central Pollution Control Board’s daily 4pm bulletin, the Capital’s Air Quality Index (AQI) deteriorated to the upper end of the “very poor” category, with a reading of 369.
Delhi’s minimum temperature fell to 7.3 degrees Celsius on Tuesday – three degrees below normal and the lowest so far this season, the Met department said, forecasting a further dip to around 6 degrees Celsius by Sunday.
According to the Central Pollution Control Board’s daily 4pm bulletin, the Capital’s Air Quality Index (AQI) deteriorated to the upper end of the “very poor” category, with a reading of 369--the highest AQI reading since November 8 (372, very poor). Delhi AQI reading was 333 (very poor)on Monday.
Experts attributed the decline in Delhi’s air quality on Tuesday to a combination of low temperatures and calm winds. Met officials said the wind is calm because a fresh western disturbance is due to influence Delhi-NCR on December 1 and 2 (Thursday and Friday), with shallow fog expected in the region Wednesday onwards.
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“When a western disturbance approaches, there is a change in wind direction. Wind becomes calm before the western disturbance hits the region. Wind speed will once again pick up from Wednesday but there will be no drop in temperature for two or three days,” said RK Jenamani, scientist at India Meteorological Department (IMD), adding this western disturbance will also increase the moisture content in the air, leading to shallow fog in the early hours.
“Until now, there was no fog as there was very little moisture in the air. Compared to northwesterly winds which are dry and cold, southeasterly winds are warmer, but bring moisture,” he added.
While calm winds on Tuesday allowed local pollutants to accumulate, the wind speed is expected to pick up to around 6-8kmph on Wednesday.
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“Meteorological conditions are highly unfavourable for the dispersion of pollutants. However, the air quality is likely to be improve slightly, but remain in the ‘very poor’ category on November 30 and December 1, before deteriorating once again on December 2, 2022,” said the Early Warning System for Delhi, a forecasting system under the ministry of earth sciences.
The CPCB classifies an AQI between 0-50 as ‘good’, between 51 and 100 as ‘satisfactory’, between 101 and 200 as ‘moderate’, between 201 and 300 as ‘poor’, between 301 and 400 as ‘very poor’ and over 400 as ‘severe’.
Delhi last recorded “severe” air on November 4, when Delhi’s AQI was 447. Since then, Delhi’s AQI has remained below 400, largely on account of relatively favourable meteorological conditions.