acquired May 26, 2012
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Most of the gases and particles suspended in our atmosphere are invisible to human eyes. But that's not the case with contrails. Look up on a clear day, and there's a good chance you'll see some of these pencil-straight cirrus clouds
crisscrossing the sky. While naturally high levels of humidity cause
cirrus clouds to form, contrails form in the wake of passing aircraft
due to the extra particles and water vapor contained in their exhaust.
Contrails are visible from space as well. At 12:05 p.m. local time (14:35 UTC) on May 26, 2012, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured a view (top) of multiple contrails off the coast of Newfoundland, Canada. The MODIS instrument on the Aqua satellite generated an image (bottom) of the same area nearly two hours later.
The contrails are arrayed in an X-shaped pattern that was likely
caused by commercial aircraft flying west. A cirrus cloud, most likely
of natural origins, is visible on the left of both images. Young
contrails with distinct edges are visible in the older image, but in the
later view the contrails have grown wispier and spread outward as winds
have blown them south and east.
The temperature and humidity of the air affects how long contrails
last. When air is dry, contrails last just seconds or minutes. But when
the air is humid, as was the case here, contrails can be long-lived and
spread outward until they become difficult to distinguish from
naturally occurring cirrus clouds. Satellites have observed clusters of
contrails lasting as long as 14 hours, though most remain visible for
four to six hours.
The long-lived, spreading contrails are of great interest to climate scientists because they reflect sunlight and trap infrared
radiation. A contrail in an otherwise clear sky reduces the amount of
solar radiation that reaches Earth’s surface, while increasing the
amount of infrared radiation absorbed by the atmosphere (as do cirrus
clouds).
These opposing effects make it difficult for scientists to pin down
the effect contrails have on climate. “Overall, contrails create
additional cirrus cloud cover,” noted Patrick Minnis,
a senior scientist at NASA's Langley Research Center. “Current
estimates indicate that contrails have a small warming effect, but the
extent of the additional coverage and the amount of warming remain quite
uncertain.”
In 2004, Minnis published a study
of surface observations that found cirrus cloud cover had increased by 3
percent between 1971 and 1995 over the United States. That's the most
recent estimate available, Minnis pointed out, because the network of
surface instruments his research group used is no longer available.
References
- King, M. (2007) Our Changing Planet: The View from Space. Cambridge University Press.
- Minnis, P. (2004, April 15). Contrails, Cirrus Trends, and Climate. Journal of Climate.
- NASA Langley. (n.d). Contrail Education. Accessed June 1, 2012.
NASA image courtesy Jeff Schmaltz, LANCE MODIS Rapid Response Team, Goddard Space Flight Center. Caption by Adam Voiland.
- Instrument:
- Aqua - MODIS
Ricardo M Marcenaro - Facebook
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Mis blogs son una casa abierta a todas las culturas, religiones y países. Se un seguidor si quieres, con esta acción usted está construyendo una nueva cultura de la tolerancia, la mente y el corazón abiertos para la paz, el amor y el respeto humano.
Gracias :)
