Dust storm in West Asia is making Mumbai air quality worse

Girgaon Chowpatty is shrouded in haze on December 29. Pic/Shadab Khan

While Mumbai is already grappling with the effects of localised pollution and winter moisture, both of which are deteriorating air quality, dust travelling from West Asia appears to be adding to Mumbaikars' woes. A dust storm originating in Iran, Afghanistan and Pakistan is exacerbating the city's already poor air quality, resulting in haze and low visibility. Experts note that a similar phenomenon occurred thrice in 2022, each time worsening the city's air quality.

On Friday, December 27, Mumbai recorded an overall Air Quality Index (AQI) of Navy Nagar in Colaba recorded an AQI of 302 (very poor) in the morning, it gradually dropped to 265 (poor) in the afternoon. At around 5 pm, other stations which recorded poor AQI in Mumbai and MMR included Borivli East (207), Malad west (265) Mazagaon (207). Meanwhile, the Maharashtra Pollution Control Board (MPCB) AQI monitoring station at Siddhivinayak Nagar in Ulhasnagar recorded an AQI value of 303 (very poor).

Buildings are veiled by smog at Girgoan on Sunday. Pic/Shadab Khan

The situation worsened further with more areas recording poor AQI values on Saturday when Borivli East (IITM) recorded an AQI value of 299 followed by Byculla (279), Deonar (203), Mazagaon (284), Malad West (253), Navy Nagar-Colaba (286), Siddharth Nagar- Worli (271), Again, on Sunday evening, while Mumbai's overall AQI remained in the moderate category at 198, several monitoring stations across the city recorded poor to very poor levels (see box).

Phenomenon explained

Dr Gufran Beig, chair-professor at the National Institute of Advanced Sciences (NIAS), said: "There are multiple dust storms emerging from border areas of Iran and Afghanistan towards the Arabian sea and eventually trying to intrude into the coastal region led by Mumbai. Meteosat dust imaging and our model output are showing some dust intrusion to the Arabian Sea from Afghanistan and Pakistan towards Mumbai. But not very significant due to winter heavy air which tends to resist longer movement. It may contribute less than 50 micrograms of PM10 to Mumbai. Heavier air allows it to descend lower. The effect will be more visible in the upper sky and less so on the ground."

Beig said that the impact of dust storms leading to deteriorating air quality in Indian cities, Mumbai in this case is not common during winter months, but a similar phenomenon was witnessed thrice in 2022 between January and February.

"The source of these dust storms is invariably desert regions in the Gulf, Iran, Afghanistan and Pakistan. Storms that occur in June and July don't typically affect Mumbai or neighbouring areas because of the Indian monsoon. In spring and summer, though, factors like high temperatures, atmospheric instability, strong northwesterly winds, and thunderstorms create ideal conditions for dust storms and subsequent pollution events. During this period, upper-level winds over the Arabian Sea become significantly stronger, allowing dust particles to travel faster. In regions stretching from Afghanistan, Pakistan and Iran to the Thar desert in Rajasthan, dust lifting becomes widespread and intense, evolving into full-fledged dust storms," Beig explained.

Impact of storm

Climatologist Rajesh Kapadia of the private weather blog Vagaries of the Weather told mid-day that Mumbai has experienced intense smog for the past eight days, with various theories circulating, ranging from construction pollution to excessive gas releases. However, Kapadia emphasised a meteorological explanation, noting that neither construction, repair work nor gas burning began specifically on December 20, nor were these activities banned before that date.

According to Kapadia, a severe dust storm developed around December 20 over Iraq and gradually moved eastward. Meteorologically, a strong anticyclone at 3.1 km and 5.8 km altitudes was centred over the Arabian Peninsula, bringing powerful winds over Gujarat and into Maharashtra from the Arabian Sea - effectively drawing dust into its circulation. Under normal conditions, air closer to the ground is warmer, while higher altitudes are cooler. During a temperature inversion, this pattern inverts, trapping colder surface air (and any suspended particles) beneath a layer of warmer air. As a result, the moist dust settled closer to ground level in Mumbai and its surrounding regions.

Certain urban areas in Mumbai saw heavier deposition due to local topography. Despite the discomfort caused by this smog, manifesting as reduced visibility and breathing difficulties, air quality in many places remained "moderate" rather than "severe." Kapadia attributes this partly to the nature of the dust and partly to the fact that it was "sucked in" by the anticyclone. He adds that the dust patch in West Asia appeared even larger on satellite images as of December 29, raising concerns that the current situation might persist or intensify.

‘It's not unusual'

Sunil Kamble, director of the India Meteorological Department in Mumbai, said, "Winter haze over many parts of the city reduces visibility because northerly or easterly winds push pollutants in. Under normal circumstances, the sea breeze would disperse these pollutants, but in its absence, suspended particles remain in the air, creating a haze blanket. Although there is a dust storm in West Asia, it's not an unusual phenomenon, and we need more study before linking it directly to Mumbai's worsening air quality. Meanwhile, local sources of pollution such as construction dust, garbage burning and vehicular emissions continue to be significant factors. The IMD regularly shares weather updates with local civic and government bodies, farmers and the defence forces. Since the BMC itself monitors air quality and visibility around the clock, it's essential that the public receives timely updates."

Independent weather enthusiast Rushikesh Agre, popularly known as ‘Mumbai Rains' on X, wrote on Sunday, "Things are likely to improve from December 30 and December 31 for Mumbai. AQI levels will come down by next week. Please take precautions, wear masks if possible."

AQI on December 29
Mumbai (overall) 198
Borivli East (IITM) 274
Byculla (BMC) 300
Kherwadi (MPCB) 246
Malad West (IITM) 274
Mazagaon (IITM) 227
Navy Nagar (IITM) 316
Shivaji Nagar (BMC) 231
Siddharth Nagar (IITM) 296