Behind Mumbai’s unusually foul air, changes in wind pattern

Subject: Geography

Context:

Over the last one month, the air quality of the financial capital is distinctly poorer compared to previous year.

Prolonged bad air quality in Mumbai-

SAFAR app is showing the overall air quality index (AQI) in Delhi is 249 (poor) while that in Mumbai is 309 (Very poor).
Mumbai has an locational advantage- its relatively cleaner air is due to strong sea breezes which sweeps the pollutant away from the land surface.
Earlier Mumbai has seen the rise in air pollutants but this time the phase of bad air quality is perticularly prolonged.

Probable reason for bad air quality-

Slower wind speed- Wind speed in mumbai is relatively slower this year, reducing its ability to sweep away pollutants.
Change in flow pattern-
- Generally, In Mumbai, the wind flows from land to sea for a few days and then from sea to land. This cycle gets repeated every 3-4 days.
- When the wind flows from land to sea, it sweeps away the pollutants.
- But this year, the cycle is getting delayed from 3-4 days to more than 10 days. This led to large scale accumulation of air pollutants over the city.
Rise in PM 10 pollutant suggests the cause of bad air quality could be large scale increases in construction activities. As PM2.5 mostly comes from vehicular or Industrial emissions of power plants, while PM10 comes from large scale construction activities.