The deep freeze gripping much of the US has been blamed on a polar vortex. Here's what that means.
from BBC News - World https://bbc.in/2Sex5LW
from BBC News - World https://bbc.in/2Sex5LW
Polar vortex: What is it and how does it happen?
![Polar vortex: What is it and how does it happen?]()
Reviewed by TUNI ON LINE CENTER AMBIKAPUR
on
जनवरी 31, 2019
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