temperature inversion

noun1

1. •
   An atmospheric condition in which a cooler layer of air lies below a warmer layer of air that functions as a "ceiling" for the cooler layer, interfering with normal atmospheric circulation and trapping pollutants.

   • It's possible that a temperature inversion—a layer of warm air lying on top of a layer of cold air—is causing the sounds of the sonic booms to be carried inland, he said. — 1993