|Thermal inversion and pollution|
|Wednesday, 13 June 2007, Written by Julien|
The last few days were really bad in Beijing, with grey sky and heavy smog. It is mainly due to thermal inversion.
You might have heard of convection. This is a natural phenomena that creates circulation in fluids from temperature differences. It is convection that creates bubbling when heating water. It happens because cold water is heavier than warm water.
Normally speaking, the same thing happens in the atmosphere, and the air heated by the ground tends to be replaced by fresh air from above. That is great to clean polluted air.
However, in some cases, air in altitude is warmer than air on the ground, so the convection cannot occur. Air stays and pollution accumulates! That's what happened those last days.
Today, the wind is back, so pollution has been taken away, air is fresher and the smog is partly gone!
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