What does cold smell like?

Just for fun, here's a picture I snapped just north of Medicine Bow, Wyoming last January when I was on my way back to Casper for my flight. The weather had been in negative digits in Laramie all week, and it was far colder out in the flats south of Shirley Basin. I can only guess, but I figure it was around ten or twelve below zero at dusk. 

So, what does this level of cold on a sub-arctic plain smell like?

Vaguely of copper, actually.