Click on image for higher resolution version (JPL).
For the second time this month, Iceland's Eyjafjallajokull volcano (pronounced "Aya-fyatla-jo-kutl") erupted. The latest eruption, on Wed., April 14, spewed a cloud of ash into the atmosphere and is disrupting air travel in Northern Europe and around the world.
The Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite flew over the volcano at 1:30 p.m. local time (13:29:24 UTC, or 6:29:24 a.m. PDT) on April 15, capturing this false-color infrared image, as well as a visible image of the ash plume. The images show the ash cloud (in blue) enveloping Iceland and moving eastward over the Shetland Islands and onward to Europe. The ash clouds appear to be at an altitude of 3,658 meters (12,000 feet).
NASA works with other agencies on using satellite observations to aid in the detection and monitoring of aviation hazards caused by volcanic ash. More information on this NASA program is at: http://science.larc.nasa.gov/asap/research-ash.html. The ingestion of ash particles from such clouds can result in engine failure for aircraft.
Because infrared radiation does not penetrate through clouds, AIRS infrared images show either the temperature of the cloud tops or the surface of Earth in cloud-free regions. The lowest temperatures (in purple) are associated with high, cold cloud tops. In cloud-free areas the AIRS instrument will receive the infrared radiation from the surface of the Earth, resulting in the warmest temperatures (orange/red).
The AIRS instrument suite contains a sensor that captures radiation in four bands of the visible/near-infrared portion of the electromagnetic spectrum. Data from three of these bands are combined to create "visible" images similar to a snapshot taken with your camera.
AIRS, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena. More information about AIRS can be found at http://airs.jpl.nasa.gov.