This phenomenon caused by differences in air temperature that is in the same area at different temperatures and stray them is absorbed into one of the locations.
This phenomenon is caused by differences in air temperature distribution in the same area is patchy and the temperature difference between them being sucked into a certain position, very special.
This phenomenon arises from the difference of air temperature distribution in the same area is inadequate, and the temperature difference is absorbed into those in any position, a position is very special.