Daily Archives: July 14, 2014

We have made reference a few times in this column to the areal extent of cold air over the Northern Hemisphere as a measure of wintertime severity, that is, the geographic reach of air of a certain temperature.

Specifically, we have reported on the 23-degree air at 1 mile above the ground (where the atmospheric pressure is just 85 percent of its near-surface value). By mid-July it is impossible to find air that cold at that elevation in the Northern Hemisphere. Continue reading →