civil twilight"The period between astronomical sunrise or sunset and the time when the sun's unrefracted center is at elevation h0 = −6°.
CIVIL TWILIGHT The time between the moment of sunset, when the sun's apparent upper edge is just at the horizon, until the center of the sun is 6° directly below the horizon. Related term: twilight ...
civil twilight—See twilight.
clear air turbulence (abbreviated CAT)—Turbulence encountered in air where no clouds are present; more popularly applied to high level turbulence associated with wind shear.
Civil twilight refers to the interval of incomplete darkness that occurs when the sun's center is approximately 6 degrees below the horizon. The amount of light is still sufficient to carry on outdoor work without the aid of artificial light.
Civil Twilight - The period of time before sunrise and after sunset when the sun is not more than 6° below the horizon.
Nautical Twilight - The period of time before sunrise and after sunset when the sun is not more than 12° below the horizon.
The time after civil twilight, when the brighter stars used for celestial navigation have appeared and the horizon may still be seen.
The average time of civil twilight, which is the time between civil dawn and sunrise in the morning, and between sunset and civil dusk in the evening.
Twister
In the United States, a colloquial term for a tornado.
NAUTICAL TWILIGHT The time after civil twilight, when the brighter stars used for celestial navigation have appeared and the horizon may still be seen.
Cirrus Cloud:Couds which are between 18,000 & 30,000 feet. Are wispy and consist of ice crystals.
Circulation: A continuous movement of air.
Civil Twilight: When the sun is no more than 6 Degs. below the horizon before sunrise and after sunset.
 See also: Twilight, Light, Weather, Cloud, Clouds
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