Light rain expected in Delhi, pollution levels remain very poor

The city recorded a minimum temperature of 7°C while the maximum temperature was expected to be around 20°C

Light rain was expected in Delhi on Thursday even as the fog continued to blanket the city in the morning while air pollution levels remained in the “very poor” category.

Dense fog has resulted in low visibility in Delhi for days. (Hindustan Times)

The city recorded a minimum temperature of 7°C while the maximum temperature was expected to be around 20°C. On Wednesday, the minimum temperature was 5.2°C, two notches below the normal, and a maximum of 21.4°C, a degree above the normal.

According to the Central Pollution Control Board (CPCB), the hourly air quality index (AQI) was 345 at 7am on Thursday. The average 24-hour AQI was 308 at 4pm on Wednesday.

An AQI between zero and 50 is considered good, 51 and 100 satisfactory, 101 and 200 moderate, 201 and 300 poor, 301 and 400 very poor, and 401 and 500 severe. The AQI in the poor category leads to breathing discomfort for most people on prolonged exposure.

On Thursday, the monitoring agency System of Air Quality and Weather Forecasting and Research (Safar) said fine particles (size < 2.5 micrometer) contributed ~ 64% to PM10. “For the next 3 days, surface wind speed (12 to 16 km/h) and temperature (Max 18-20 deg C; Min 8-9 deg C) are likely to improve air quality. Mixing layer height is likely to be ~ 1.0 km that causes moderate ventilation of pollutants.”

The air quality was likely to improve but remain “very poor” for the next three days due to low temperatures (which help the accumulation of pollutants) and moderate surface winds (that cause moderate dispersion of pollutants). “Morning fog is likely at isolated places. Wind flow from northwest region experiencing subsided cold wave is likely to increase the temperature for next 3 days that improves air quality.”