Unique Space Image of Alabama Tornado Tracks May 16, 2011: NASA has released a   
   unique satellite image tracing the damage of a monster EF-4 tornado that tore   
   through Tuscaloosa, Alabama, on April 27th. It combines visible and infrared   
   data to reveal damage unseen in conventional photographs.   
       
   "This is the first time we've used the ASTER instrument to track the wake of a   
   super-outbreak of tornadoes," says NASA meteorologist Gary Jedlovec of the   
   Marshall Space Flight Center in Huntsville, AL.   
   [...]   
   An ASTER visible-IR image of tornado damage near Tuscaloosa, AL. [larger image]   
       
   In the picture, captured just days after the storm, pink represents vegetation   
   and aqua is the absence of vegetation. The tornado ripped up everything in its   
   path, scouring the Earth's surface with its terrible force. The "tearing up"   
   of vegetation makes the tornado's track stand out as a wide swath of aqua.   
       
   "This image and others like it are helping us study the torn landscape to   
   determine just how huge and powerful these twisters were and to assess the   
   damage they inflicted," says Jedlovec.   
       
   ASTER, short for Advanced Spaceborne Thermal Emission and Reflection   
   Radiometer, orbits Earth onboard NASA's Terra spacecraft. Its data products   
   include digital elevation maps from stereo images; surface temperatures;   
   vegetation maps; cloud and sea ice data; and more. Last spring the instrument   
   helped track the movement of the oil spill in the Gulf of Mexico.   
   [...]   
   Ground survey teams have a lot to contend with. [Youtube video] To detect the   
   scars left by the twisters, ASTER senses the visible and infrared energy   
   reflected from the planet's surface. Destruction like crushed houses, torn and   
   snapped trees, and uprooted crops are evident in the multi-wavelength images.   
       
   "A demolished house, debris and soil scattered on vegetated surfaces, and   
   damaged trees and crops all change the pattern of reflected radiation measured   
   by the satellite," explains Jedlovec. "We can analyze these patterns to help   
   storm survey teams evaluate the damage."   
       
   Ground teams conducting field surveys of tornado damage must try to pinpoint   
   where the twisters touched down, how long they stayed on the ground, and the   
   force of their winds. But doing this from ground level can be tricky. Some   
   places are nearly impossible to reach by foot or car. Also, in remote areas,   
   damage often goes unreported, so survey teams don't know to look there.   
       
   This is where satellites can help.   
       
   "To get an accurate picture survey teams need to look everywhere that   
   sustained damage - even unreported areas. Satellite sensors detect damage in   
   rural areas, wilderness areas, and other unpopulated areas. Only with that   
   knowledge can surveyors determine the true track of a tornado."   
       
   Otherwise, says Jedlovec, a twister could have flattened a single dwelling in   
   a remote location, killing everyone inside, and no one would know.   
   [...]   
   Another sample of ASTER tornado data showing three nearly-parallel tracks of   
   destruction. [large image] [annotated composite image]   
       
   Less critical but still important are home owners' insurance issues. To   
   evaluate claims submitted by storm victims, insurance companies rely on   
   National Weather Service storm reports based on the field surveys.   
       
   "Let's say you live in a remote area," says Jedlovec. "If there's no record of   
   a storm passing over your area, you could be out of luck."   
       
   Jedlovec and colleagues are working now to produce satellite images of other   
   areas ravaged by the historic outbreak of tornadoes.   
       
   "We want to help the storm victims any way we can."   
       
   Author: Dauna Coulter | Editor: Dr. Tony Phillips | Credit: Science@NASA   
       
   More Information   
   ASTER Home Page   
       
   Terra Home Page   
       
   Gary Jedlovec heads up the SPoRT (Short-term Prediction and Research   
   Transition) project at the Marshall Space Flight Center in Huntsville,   
   Alabama, a city that was spared the worst of the damage, though an EF-5   
   tornado just missed it, destroying communities only a few miles away.   
       
   SPoRT personnel created the NASA images in this story using data provided   
   courtesy of NASA Goddard Space Flight Center, the Land Processes Distributed   
   Active Archive Center, Japan's Earth Remote Sensing Data Analysis Center, the   
   Ministry of Economy, Trade and Industry, along with the Japan Research   
   Observation System Organization.   
   [...]   
   The ASTER image in this story came from an observation on May 4, 2011 at 11:45   
   A.M. local time (1645 UTC), and shows the tornado track was roughly 80.3 miles   
   (129.2 kilometers) long and up to 1.5 miles (2.4 kilometers) wide.   
       
   For more information on using remote sensing to track tornado damage paths,   
   see this paper by Jedlovec.   
       
       
   Regards,   
       
   Roger   
      
   --- D'Bridge 3.61   
    * Origin: NCS BBS (1:3828/7)