What characterizes a downburst?

A downburst is characterized by a severe downward rush of air that can produce damaging winds upon reaching the ground. This phenomenon occurs when a column of air becomes rapidly cooled by precipitation or evaporative cooling, causing it to sink. When this cold, dense air reaches the surface, it spreads out, often resulting in intense horizontal winds that can cause significant damage to structures, vegetation, and aircraft during takeoff and landing.

The other options do not accurately describe a downburst. Gentle upward air movements are characteristic of other phenomena, such as thermals or updrafts, rather than the downward motion of a downburst. A constant horizontal wind flow does not characterize a downburst, as it specifically involves strong, turbulent air rushing downward and then outwards, not consistent horizontal winds. Finally, a gradual decrease in air pressure might relate to different meteorological concepts but does not depict the rapid and intense nature of the air movement associated with a downburst.