Slight decline in air quality as winds change

Low wind speed and a change in wind direction led to a marginal decline in Delhi’s air quality on Friday. The India Meteorological Department (IMD) forecast said

Low wind speed and a change in wind direction led to a marginal decline in Delhi’s air quality on Friday. The India Meteorological Department (IMD) forecast said Delhi and neighbouring cities are likely to receive light rainfall starting Friday night.

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The Central Pollution Control Board (CPCB) data shows that the overall air quality index (AQI) of Delhi was 295, in the poor category. On Thursday, the AQI was 284, also in the poor category.

Kuldeep Srivastava, head of IMD’s regional weather forecasting centre, said on Friday, the average wind speed was 6kmph, which was not enough to blow away the pollutants. However, with a western disturbance impacting the entire region, the pollution levels are not expected to worsen much over the weekend.

“The wind speed reduced to 6kmph and the direction also changed from north-westerly to easterly on Friday. Some areas in Haryana have received rainfall on Friday afternoon,” said Srivastava.

He said the average wind speed in Delhi is likely to remain around 8-10kmph on Saturday and Sunday, which means that the air quality is likely to remain in the “poor” zone till Monday.

“The western disturbance will pass on Saturday and the wind direction will change back to north-westerly,” he added.

The Union ministry of earth science’ air quality monitoring centre, System of Air Quality and Weather Forecasting and Research (Safar), said under the influence of this western disturbance, isolated to scattered rainfall and better ventilation are expected on Friday and Saturday and the AQI is also likely to further improve to the moderate category or the lower end of poor category.

“However, the respite is not expected to last long. As an aftermath of the western disturbance, high moisture availability and higher air holding capacity will result in the creation of dense fog (mainly during early morning hours). This will lead to a deterioration in air quality from December 14,” the Safar forecast said.

IMD scientists also said from December 14, the temperature is also expected to start falling. On Friday, the minimum temperature recorded at the Safdarjung observatory, which is considered the official marker for the city, was 11.3 degrees Celsius. This was two notches above the season’s normal. The maximum temperature was 25.8 degrees Celsius, three degrees above normal.