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

GS Paper 1

Syllabus: Geographical phenomenon and their environmental impacts


Source: IE 

Direction: The article mainly highlights how local winds like sea breezes could influence the pollution level of a place.

 Context: Over the last month, air quality in India’s financial hub, Mumbai, has been noticeably worse than in prior years, giving Mumbaikars a taste of what people in Delhi have become used to at this time of year.

 Background: Since December 5, the AQI in Mumbai has consistently been in the “very poor” range (AQI > 300), according to the SAFAR (System of Air Quality and Weather Forecasting and Research) network.

 Why is this unusual?

  • This is not the first time Mumbai’s air has been so toxic, but it has never lasted more than 1-2 days.
  • Though Mumbai generates pollutants in equivalent amounts as compared to Delhi, it has an important location advantage.
    • Mumbai’s relatively clean air is the result of strong sea breezes that sweep air pollutants away from the land.


Reasons for this unusual pattern:

  • Change in flow patterns: In Mumbai, winds move from land to sea for a few days and then from sea to land and this cyclic pattern usually repeats every 3-4 days.
    • When the wind is not moving away from the land, air pollutants accumulate over the city. But then the wind direction changes, and it all gets cleaned.
    • This cycle is delayed this year. Instead of repeating every 3-4 days, it is happening after a week, even 10 days.
    • Even when the wind direction turns favourable, the lack of adequate speed means that the air is not entirely cleaned.

Probable causes:

  • Though the meteorological reasons behind this change needed to be probed, this can be attributed to some unusual global events like the third consecutive year of La Niña.
    • La Nina is an abnormal cooling of the Pacific Ocean that impacts weather events across the world.
  • More construction activities: Large infrastructure projects, like the Mumbai Metro or the Coastal Road Project, could be generating significantly higher amounts of pollutants.
    • This could be possible, as Mumbai is currently witnessing a rise in PM10 (particulate matter of the size of 10 micrometres or smaller) levels as well.


About SAFAR:

●        It is an initiative of the Union Ministry of Earth Sciences (MoES) launched in 2010 (for Delhi) for greater metropolitan cities to provide –

○        Location-specific information on air quality in near real-time and

○        It’s forecast 1-3 days in advance.

●        It is developed by the Indian Institute of Tropical Meteorology, Pune, and is operationalised by the India Meteorological Department (IMD).

●        SAFAR framework considers almost all pollutant levels – PM10, 1, 2.5, CO, NOx, SO2, Volatile Organic Compounds, etc., to compile the Air Quality Index (AQI).

●        It promotes public awareness by educating the public, encouraging self-mitigation, and assisting policymakers in developing mitigation policies.


Insta Links:

Land and Sea Breezes


Mains Links:

Q. Explain local winds and how they impact the weather condition of a region? (250 words)


Prelims Links:

Consider the following statements:

  1. The air pressure is highest at sea level and decreases with height.
  2. In nature, the air always moves from high-pressure areas to low-pressure areas.
  3. Low-pressure systems are usually characterised by dry and settled weather.

Which of the above statements is/are correct?

    1. 1, 2
    2. 1, 3
    3. 2, 3
    4. 1, 2 and 3

Solution: 1)

Air pressure is defined as the pressure exerted by the weight of air on the earth’s surface. As we go up the layers of the atmosphere, the pressure falls rapidly.

In areas where the temperature is high the air gets heated and rises. This creates a low-pressure area. Low pressure is associated with cloudy skies and wet weather.

  • In areas having lower temperatures, the air is cold. It is therefore heavy.
  • Heavy air sinks and creates a high-pressure area. High pressure is associated with clear and sunny skies.
  • In nature, the air always moves from high-pressure areas to low-pressure areas.