100px|A sky filled with many types of cirrus clouds

Cirrus clouds are atmospheric clouds characterized by thin, wispy strands, often bunched into tufts. They range in color from white to a faint gray and form when water vapor undergoes deposition at altitudes above 5,000 m (16,500 ft) in temperate regions and above 6,100 m (20,000 ft) in tropical regions. They also form from the outflow of tropical cyclones or the anvils of cumulonimbus clouds. Since these cirrus clouds arrive in advance of the frontal system or tropical cyclone, it indicates that the weather conditions may soon deteriorate. While they indicate the arrival of precipitation, cirrus clouds themselves produce only fall streaks (falling ice crystals that evaporate before landing on the ground). Jet stream-powered cirrus clouds can grow long enough to stretch across continents, but they remain only a few kilometers deep. When visible light interacts with the ice crystals in cirrus clouds, it produces glories, sundogs, and fire rainbows. Cirrus clouds raise the temperature of the air beneath them by an average of 10 °C (18 °F). (more...)

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_______________________________ Today's selected anniversaries:

1829:

The Metropolitan Police of Greater London, originally headquartered in Great Scotland Yard, Westminster, was founded. http://en.wikipedia.org/wiki/Metropolitan_Police_Service

1962:

Alouette 1, Canada's first satellite, and the first satellite operated by a country other than the Soviet Union or the United States, was launched. http://en.wikipedia.org/wiki/Alouette_1

1963:

The University of East Anglia was founded in Norwich, England, after talk of establishing such a university in the city began as early as the 19th century. http://en.wikipedia.org/wiki/University_of_East_Anglia

2006:

Gol Transportes Aéreos Flight 1907 collided in mid-air with an Embraer Legacy business jet near Peixoto de Azevedo, Mato Grosso, Brazil, killing 154 total people, and triggering a Brazilian aviation crisis. http://en.wikipedia.org/wiki/Gol_Transportes_A%C3%A9reos_Flight_1907

_____________________________ Wiktionary's word of the day:

abnegate (verb): 1. To deny oneself (something), to renounce or give up (a right, power, claim, privilege or convenience). 2. To deny, to reject (something, for example a truth or a commonly-held belief) http://en.wiktionary.org/wiki/abnegate

___________________________ Wikiquote quote of the day:

The truth is that my work — I was going to say my mission — is to shatter the faith of men here, there, and everywhere, faith in affirmation, faith in negation, and faith in abstention in faith, and this for the sake of faith in faith itself; it is to war against all those who submit, whether it be to Catholicism, or to rationalism, or to agnosticism; it is to make all men live the life of inquietude and passionate desire. --Miguel de Unamuno http://en.wikiquote.org/wiki/Miguel_de_Unamuno