Temperature Inversion

A layer of the atmosphere where temperature increases with altitude rather than decreasing at the normal lapse rate. Inversions act as a cap that traps pollutants, haze, fog, and smoke below the inversion level, often resulting in poor visibility near the surface. They are commonly caused by surface radiational cooling on clear, calm nights or by warm air overriding cold air at a frontal boundary. Pilots climbing through an inversion layer will notice a rapid improvement in visibility and a wind shift, while below the inversion, conditions can be deceptively hazy or foggy.