atmospheric extinction
atmospheric extinction The loss of starlight in passing through the Earth's atmosphere. Most of the loss arises from
Rayleigh scattering by molecules of nitrogen and oxygen. At certain wavelengths there is
selective absorption from molecules of oxygen, ozone, and water vapour. Particles of dust and industrial pollutants can also contribute to extinction by
Mie scattering. Atmospheric extinction is proportional to the
airmass and the atmospheric pressure. At sea level and in a perfectly clear sky a star 80° from the zenith appears 1 mag. fainter than it would at the zenith. This in turn is 0.3 mag. fainter than if no atmosphere were present. These figures apply only to visual observations; in blue light, the extinction is greater, while in red light it is less. This is why the Sun and Moon in particular appear red when near the horizon.
atmospheric extinction
zenith distance ° | Extinction (relative to zenith) mag. |
|---|
85 | 1.75 |
80 | 1.00 |
75 | 0.65 |
70 | 0.45 |
60 | 0.25 |
50 | 0.10 |
40 | 0.05 |
Cite this article
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Permafrost: A Guide to Frozen Ground in Transition.(Book Review)
Magazine article from: Northern Review; 6/22/2005; ; 700+ words
; Permafrost: A Guide to Frozen Ground in Transition...the public. His latest contribution, Permafrost: A Guide to Frozen Ground in Transition...resource managers, and land use planners. Permafrost is an engaging and delightful exploration...
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 "Wisconsin State Journal (Madison, WI)")
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THAWING PERMAFROST MAY HEAT THINGS UP GASES RELEASED A SLOW-MOTION TIME BOMB'.(FRONT)
Newspaper article from: Wisconsin State Journal (Madison, WI); 9/7/2006; 700+ words
; ...soil are bubbling out of the thawing permafrost in amounts far higher than previously...dioxide -- is being released from the permafrost at a rate five times faster than thought...forecast: Warming already under way thaws permafrost, soil that has been continuously frozen...
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Melting Arctic permafrost threatens homes and roads
Newspaper article from: China Daily; 12/22/2005; 700+ words
; ...almost all of the top layer of Arctic permafrost by the end of the century. Scientists...of carbon stored in the soil. If the permafrost does thaw, as our model predicts...major influence on climate." Thawing permafrost is one of several climate "tipping...
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Circum-Arctic map of permafrost and ground ice conditions.
Magazine article from: Arctic; 9/1/1998; 700+ words
; ...Simon W. Muller coined the word permafrost. At first some linguistic purists...Permalift brassieres. But the term permafrost has stuck in English, and here...s team from the International Permafrost Association presents a multitude...
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Permafrost thaw releases much more gas than thought: Scientists worry global warming could become greatly accelerated
Newspaper article from: Charleston Gazette; 9/7/2006; ; 700+ words
; ...soil are bubbling out of the thawing permafrost in amounts far higher than previously...dioxide - is being released from the permafrost at a rate five times faster than thought...forecast: Warming already underway thaws permafrost, soil that has been continuously frozen...
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United States : Surface Permafrost Likely to Vanish in Alaska.
News Wire article from: TendersInfo; 11/9/2009; 700+ words
; ...probably will see most of its surface permafrost vanish by the end of this century...increase. The future of Alaska's permafrost is being closely watched by scientists...Geophysical Institute, discussed evolving permafrost research this week during a teleconference...
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A Place in the Permafrost For the Woolly Mammoth
Newspaper article from: The Washington Post; 10/6/1997; ; 700+ words
; ...as a "she." So for Siberians, permafrost is a lady -- "a wild one," said scientist Tatiana Botulu. "Permafrost may look calm and composed, and...which is dedicated to the study of permafrost, the slab of the Earth's crust...
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Permafrost May Be Shrinking Arctic Lakes
News Wire article from: AP Online; 6/4/2005; ; 700+ words
; ...Siberia and concluded that lakes where permafrost remains frozen are growing. But lakes where permafrost has become mushy are shrinking or disappearing...Arctic lakes are shrinking, and melting permafrost brought on by higher temperatures may...
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EAST LANSING, Mich.: Climate Change and Permafrost Thaw Alter Greenhouse Gas Emissions in Northern Wetlands
News Wire article from: Targeted News Service; 8/8/2007; 700+ words
; ...issued the following press release: Permafrost - the perpetually frozen foundation...and cons when terra firma goes soft. Permafrost serves like a platform underneath vast...are rooted, literally, in melting permafrost in many northern ecosystems. But rising...
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Bad sign for global warming: Thawing permafrost holds vast carbon pool.(Report)
Newspaper article from: NewsRx Health & Science; 9/21/2008; 700+ words
; Permafrost blanketing the northern hemisphere contains...have estimated the carbon contained in permafrost in northeast Siberia. The new research expands that estimate to the rest of the permafrost-covered northern latitudes of Russia...
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permafrost and climate change
Book article from: The Oxford Companion to the Earth
permafrost and climate change Areas of permafrost are usually defined as those regions of the world in which...of thousands of years). The thickest accumulations of permafrost in the world presently occur in north-eastern Siberia...
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permafrost
Book article from: The Oxford Companion to the Earth
permafrost Permafrost is ground that remains at or below 0°C for at least 2 years. About one-quarter of the Earth's land surface is underlain by permafrost, including over half of Canada and Alaska, the Tibetan Plateau...
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Permafrost
Encyclopedia entry from: The Gale Encyclopedia of Science
Permafrost Geologists define permafrost as soil or rock that remains frozen for a time period in excess of two years. The composition of permafrost can vary widely depending on the geology and geomorphology...
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permafrost table
Book article from: A Dictionary of Ecology
permafrost table The upper limit of permafrost . Compare tjaele .
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rock glaciers
Book article from: The Oxford Companion to the Earth
...flows only slowly. A second ‘permafrost model’ explains the slow...necessary. It does, however, demand permafrost conditions (usually seen as a mean...glaciers have been used as indicators of permafrost (or past permafrost if relict features...
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