‘Poor’ AQI as westerly winds blow dust over city

Mumbai Air quality in the city has plummeted over the past week, with the System of Air Quality and Weather Forecasting And Research’s (SAFAR) network of monitors recording an air quality index (AQI) of 252, which is in the ‘poor’ category, on Friday evening.

However, this is a slight improvement from earlier in the day, when the AQI had settled at 309, indicating ‘very poor’ air quality.

Officials attributed the worsening AQI to prevailing weather systems. “Westerly winds are blowing dust over Mumbai and the Konkan region, which have been brought from the Thar desert and beyond. Because of prevailing weather systems, including higher than normal temperatures in north India and arrival of monsoon over the Andaman Sea, there is a lot of humidity in the air, which is holding the dust back and pushing up pollution levels,” said Gufran Beig, project director, SAFAR.

However, Beig clarified that the ongoing pollution spell is not a dust storm event. “Air quality has been worsening steadily for the last few days. It’s the result of a transitional phase between seasons, which will subside soon. Winds may become strong enough to disperse the suspended particles,” he added.

Mumbai’s air quality had last shown such deterioration in late February, when the third successive dust storm to affect Mumbai in one month had emerged from the west of the city on February 24. The dust was highly widespread and engulfed the entire Arabian Sea, as shown by satellite imagery. The incursion of dust into Mumbai was gradual due to slow but consistent westerly winds, which were the result of a western disturbance which had recently passed over north India.

Meanwhile, temperatures in the city remained normal, with a daytime maximum reading of 33.4 degrees Celsius on Friday, and minimum nighttime reading of 29 degrees Celsius, two degrees above normal. As per the IMD’s seven-day forecast for the city, there may be a chance of some pre-monsoon showers around May 25. Day and nighttime temperatures are expected to hover around 34-35 degrees 27-28 degrees, respectively.

An AQI of 100 to 199 is considered ‘moderate’, while 50 to 99 is considered ‘satisfactory’ and below 50 is considered ‘good’. AQI in excess of 200 is considered ‘poor’, above 300 ‘very poor’, above 400 ‘severe’ and above 500 is considered ‘severe+’.