Visibility generally refers to the quality of vision through the atmosphere. Technically, this term denotes the greatest distance in a given direction that an observer can just see a prominent dark object against the sky at the horizon with the naked eye. Visibility is a measure commonly used in the observance of weather in the United States. In this context, surface visibility refers to visibility determined from a point on the ground, control tower visibility refers to visibility observed from an airport control tower, and vertical visibility refers to the distance that can be seen vertically into a ground-obscuring medium such as fog or snow.

Visibility is affected by the presence of aerosols or haze in the atmosphere. In the ideal case of a black target on a white background, the target can be seen at close range because it reflects no light to the eye, while the...