Why are winters in Delhi so polluted?
Winter air in Delhi can get really polluted. The AQI is dangerously unhealthy. Why is this so? Why is this only happening during winter and not during summer? Take a moment to think about this.
Cool air sinks because cool air is denser than hot air. As it is compressed, it is heavier and thus sinks. The opposite thing happens with hot air. In the summers, because the ground is really hot, all the air close to it will rise taking the pollution with it. However, in winter months, the exact opposite happens and the pollutants get trapped close to the ground thus creating a huge layer of polluted air next to the ground.
There are multiple ways to visualise it- the most prominent being these two:
Take a water tank approximately 20cm * 30cm * 1cm and make a make-shift waterproof division between them. Pour hot water on one side- let there be a few drops of red food coloring added to this warm water. Pour cold water on the other side- let there be a few drops of blue food colouring added to this cold water. The colour of food colouring can be different as long as you can differentiate between the hot and cold water. Now, with a jerk, pull out the divider out and let the water mix. You can see the hot water (red water) come to the top while the cold water (blue water) come to the top.
The second way to do this is by taking 4 identical bottles. Fill 2 with hot red water and 2 with cold blue water (again colour doesn't matter as long as you can see the difference) to the brim. Now put a playing card (any waterproof card will work) on top of a hot water bottle and tip it over to put it on top of a cold water bottle. Put them brim to brim and pull the playing card out. Do the same thing again but here put the cold water bottle on top of the hot water bottle. You can see that in both the pairs the cold water stays down and the hot water comes up.
So next time you are in Delhi in the winter months think about why the poisonous air is blanketing Delhi. (My bad, think about that after you flee from Delhi) :-)
Cool air sinks because cool air is denser than hot air. As it is compressed, it is heavier and thus sinks. The opposite thing happens with hot air. In the summers, because the ground is really hot, all the air close to it will rise taking the pollution with it. However, in winter months, the exact opposite happens and the pollutants get trapped close to the ground thus creating a huge layer of polluted air next to the ground.
There are multiple ways to visualise it- the most prominent being these two:
Take a water tank approximately 20cm * 30cm * 1cm and make a make-shift waterproof division between them. Pour hot water on one side- let there be a few drops of red food coloring added to this warm water. Pour cold water on the other side- let there be a few drops of blue food colouring added to this cold water. The colour of food colouring can be different as long as you can differentiate between the hot and cold water. Now, with a jerk, pull out the divider out and let the water mix. You can see the hot water (red water) come to the top while the cold water (blue water) come to the top.
The second way to do this is by taking 4 identical bottles. Fill 2 with hot red water and 2 with cold blue water (again colour doesn't matter as long as you can see the difference) to the brim. Now put a playing card (any waterproof card will work) on top of a hot water bottle and tip it over to put it on top of a cold water bottle. Put them brim to brim and pull the playing card out. Do the same thing again but here put the cold water bottle on top of the hot water bottle. You can see that in both the pairs the cold water stays down and the hot water comes up.
So next time you are in Delhi in the winter months think about why the poisonous air is blanketing Delhi. (My bad, think about that after you flee from Delhi) :-)
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