Wiktionary
nuclear airburst
n. the explosion of a nuclear weapon at such an altitude that the fireball remains above the ground
Usage examples of "nuclear airburst".
He must have been caught within the line-of-sight of a nuclear airburst, at a range short enough to cause those burns.
It wasn't actually a bunker, but whoever had made the construction plans for the place had evidently thought that the control room should have the same sort of protection as those at the Leninsk Cosmodrome, or maybe he'd thought that the mountain might someday be subjected to a nuclear airburst attack.