Mumbai’s air quality improves with ‘wind reversal’ impact

Girgaon Chowpatty is covered in smog on Tuesday. Pic/Sameer Markande

Experts state that Mumbai's AQI has improved due to the impact of ‘wind reversal'. The AQI readings by the System of Air Quality and Weather Forecasting and Research (SAFAR) and Central Pollution Control Board's SAMEER app on Monday evening were 140, classified as "moderate."

The city's AQI had been deteriorating due to slow winds and the retention of moisture-retaining pollutants in the air. Over the past week, overall AQI readings in
Mumbai consistently exceeded 170 and 180. However, owing to increased wind speed and reduced moisture content, Monday's AQI dropped below 150.

AQI levels fall within different categories: ‘good' (0-50), ‘satisfactory' (51-100), ‘moderate' (101-200), ‘poor' (201-300), ‘very poor' (301-400), and ‘severe' (beyond 400).

Last week, various parts of the city recorded AQI levels crossing 200. On Friday, the overall Air Quality Index (AQI) for Mumbai reached 180, placing it on the higher end of the moderate category. Experts had anticipated elevated AQI levels until a change in wind direction occurred. They attribute the improved air quality to wind reversal.

Explaining the process, Dr Gufran Beig, a senior scientist and former project director of SAFAR, said, "Mumbai is surrounded by the ocean on three sides, resulting in typically stronger surface winds. Occasionally, the wind reverses direction. When oceanic breezes blow, they are clean and sweep away the city's pollution, improving the AQI. Conversely, when they come from the opposite direction, the AQI deteriorates. Mumbai benefits from cleaner winds from the ocean, significantly improving air quality at intervals of five to eight days."

The AQI at two stations dropped below 100 (satisfactory category). Khindipada, Bhandup West, recorded an AQI value of 80, followed by Mazgaon (92) and Byculla (95). Except for Chembur and Shivaji Nagar, Govandi, with AQI values of 286 and 231 respectively on Monday evening, falling into the ‘Poor' category, other stations remained in the ‘moderate' category.

140
Mumbai's AQI reading on Monday