Aeronautical Terms beginning with V

Vapor pressure

In meteorology, the pressure of water vapor in the atmosphere. Vapor pressure is that part of the total atmospheric pressure due to water vapor and is independent of the other atmospheric gases or vapors.

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Vapor trail

Same as condensation trail—a cloud-like streamer frequently observed to form behind aircraft flying in clear, cold, humid air.

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Veering

Shifting of the wind in a clockwise direction with respect to either space or time; opposite of backing. Commonly used by meteorologists to refer to an anticyclonic shift (clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere).

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Vertical visibility

The distance one can see upward into a surface based obscuration; or the maximum height from which a pilot in flight can recognize the ground through a surface based obscuration.

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Virga

Water or ice particles falling from a cloud, usually in wisps or streaks, and evaporating before reaching the ground.

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Visibility

The greatest distance one can see and identify prominent objects.

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Visual range

Runway visual range. An instrumentally derived horizontal distance a pilot should see down the runway from the approach end; based on either the sighting of high intensity runway lights or on the visual contrast of other objects, whichever yields the greatest visual range.

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Vortex

In meteorology, any rotary flow in the atmosphere.

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Vorticity

Turning of the atmosphere. Vorticity may be imbedded in the total flow and not readily identified by a flow pattern. Types are: absolute, negative, positive, and relative vorticity.

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