How does air pollution affect monsoon rains in India?
The adverse effects of air pollution on human health are well-established. Now, scientists agree that pollutants interfere with the differential heating of land and sea and reduce the country-wide rainfall by at least 10 per cent and also cause extreme weather events like unusually heavy rainfall.
Mechanism of cloud formation
- Clouds are made of water droplets or ice crystals that are so small and light they are able to stay in the air.
- The water or ice that make up clouds travels into the sky within air as water vapour. Water vapour gets into air mainly by evaporation as some of the liquid water from the ocean, lakes, and rivers turns into water vapor and travels in the air.
- When air rises in the atmosphere it gets cooler and is under less pressure. When air cools, it’s not able to hold all of the water vapor it once was. Air also can’t hold as much water when air pressure drops. The vapour becomes small water droplets or ice crystals and a cloud is formed.
Effects of air Pollution on Monsoon:
- Excess aerosols, suspended solid particles like dust, smoke and industrial effluents, in the atmosphere change cloud patterns, its shape, size and other properties like temperature, which in turn result in variability in rainfall over the Indian sub-continent during the monsoon season.
- “Air pollution does not allow the landmass to warm up to the required levels. Due to the presence of pollutants, heating of land takes place at a slower rate. For instance, the required surface temperature is 40°C (degrees celsius), while the presence of air pollution will result in restricting temperature up to 38°C or 39°C.”
- Atmospheric water forms deposits on naturally occurring particles, like dust, to form clouds. But if there is pollution in the atmosphere, the water is bound to deposit on more particles.
- Spread thin, the water forms smaller droplets, which in turn take longer to coalesce and form raindrops. In fact, rain may not ever happen, because if the clouds last longer they can end up moving to drier air zones and evaporating.
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