Plain English Meaning

When the ground heats up unevenly, warm air rises over the hot spots and cooler air sinks over the cooler spots. This up-and-down movement of air is what makes flying bumpy on a sunny afternoon.

Full Definition

Vertical movements of air caused by uneven heating of the Earth's surface. Surfaces such as pavement, plowed fields, and rocky terrain absorb and release heat faster than water, vegetation, or forested areas. The warmer surfaces heat the air above them, causing that air to rise, while cooler air over adjacent surfaces sinks to replace it. The result is a pattern of rising and descending air columns that produce bumpy, turbulent flight conditions, especially at lower altitudes on warm days.

Context Anchor

Seen in wind and turbulence discussions, especially when flying over sun-heated pavement, dry fields, hillsides, or other surfaces that warm faster than nearby areas.