Three reasons why Mumbai remains under smog blanket

Sub: Geo

Sec: Climatology

Context:

Mumbai has been under a blanket of smog for three consecutive days. Mumbai has been experiencing deteriorating air quality, with the Air Quality Index (AQI) fluctuating between moderate and poor over the past few days.

Factors Contributing to Smog:

Emissions from vehicles, construction sites, industries etc.
Low Humidity and Dry Weather: Mumbai is experiencing low moisture levels, contributing to dry weather and reduced humidity. Low humidity prevents water vapour from forming droplets on which particulate matter (PM) can cling to.
High Vertical and Horizontal Wind Speeds: The layer of pollutant cloud keeps getting pushed higher due to high vertical wind speeds (eddy diffusion) until it reaches the inversion layer which does not allow it to go further up. So, the pollution cloud hangs in the atmosphere just below the inversion layer in the sky, making it look hazy from the ground.

Challenges in AQI Monitoring:

Mumbai’s AQI data may not fully represent the city’s pollution levels as many monitoring stations are located in greener areas, potentially underreporting pollution.
The SAFAR-mobile app, which provides early warnings, is currently non-functional.
Data from Central Pollution Control Board (CPCB) shows disparities.

Air Quality Index:

Launched in 2014 with One Number – One Colour -One Descriptionfor the common man to judge the air quality within his vicinity.
The measurement of air quality is based on eight pollutants, namely: Particulate Matter (PM10), Particulate Matter (PM2.5), Nitrogen Dioxide (NO2), Sulphur Dioxide (SO2), Carbon Monoxide (CO), Ozone (O3), Ammonia (NH3), and Lead (Pb).
Each of these pollutants is given a weight based on a formula. That weight depends on the kind of impact it has on human health.
AQI has six categoriesof air quality. These are: Good, Satisfactory, Moderately Polluted, Poor, Very Poor and Severe.
It has been developed by the CPCB in consultation with IIT-Kanpur and an expert group comprising medical and air-quality professionals.