Apr 22, 1999

Stepping back to get a closer view

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Every day is Earth Day for climate scientists


GHCC researchers will use Landsat 7 images for a closer look at terra firma


April 22, 1999: Even though they deal mostly with water, scientists at the Global Hydrology and Climate Center (GHCC) are looking forward to getting data from a satellite designed to study land.

"Landsat 7 is going to help us out tremendously in urban heat island studies," said Dale Quattrochi, a NASA scientist at the GHCC in Huntsville, Alabama. Quattrochi and Jeff Luvall are the GHCC's lead scientists studying urban heat island phenomenon. The central effort has been the long-term Project ATLANTA (ATlanta Land-use ANalysis: Temperature and Air-quality) which includes a University of Georgia team led by Dr. C.P. Lo. The results of Project Atlanta led to 1998's Urban Heat Island Pilot Project (UHIPP) which conducted similar measurements over Baton Rouge, Sacramento, and Salt Lake City.

Right: An image from the Landsat 5 thermal channel (top) is shows how hot areas (red) correspond with urban areas (gray) in the false-color image of Atlanta (below). Credit: NASA and University of Georgia


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At the core of the urban heat island effect is the fact that the evaporation of water absorbs a large quantity of heat. Plants, and trees in particular, evaporate large amounts of water from their leaves. Trees are also very effective in shading the ground, thus preventing the heating of the surface by sunlight.


On the other hand, asphalt, concrete, and other manmade materials are very effective at absorbing light and reradiating it as infrared radiation that raises the temperature of the air. In turn, that makes air-conditioning systems work harder, even after sunset.


Dr. Dale Quattrochi, one of the lead scientists on the urban heat island study, was recognized as a world leader in the field of thermal infrared remote sensing by the Association of American Geographers' Remote Sensing Specialty Group. Quattrochi received the group's Outstanding Contributions Medal for 1999 at the group's annual convention in Hawaii. The Outstanding Contributions Medal is the only award presented in the remote sensing field by the AAG. Quattrochi is one of only two NASA or non-academic researchers to receive the award since its inception in 1980. Quattrochi earned a doctorate in geography from the University of Utah in Salt Lake City, a master's degree from the University of Tennessee in Knoxville and a bachelor's degree from Ohio University in Athens.
Luvall, Quattrochi, and the Project ATLANTA team - especially Lo, who produced the Landsat maps of land use change and heat island change through time - have used these satellite data as an integral part of our project to relate land use changes with aircraft data collected over Atlanta in 1997.

"Landsat 7's 15-meter-resolution black-and-white images will be very useful in combining with digital data to give us a better idea of what happens on the ground," Quattrochi said.

The thermal infrared channel on Landsat 7's Enhanced Thematic Mapper will see details as small as 60 meters (188 feet) on the ground as compared to 120 meters (376 feet) with prior Landsats' thermal channels.

"It's a great improvement," Luvall said. "It will give us a temporal distribution across the years and the seasons" to show trends in urban heating. The scientists still need to use aircraft, as in 1998's UHIPP, for detailed images to pinpoint individual heat sources. Aircraft are also needed to provide images to show heat storage the night immediately after a daytime observation since Landsat's orbit does not provide that sort of coverage.




Red dots show the urbanization of Atlanta and environs in a period of almost two decades. The images are derived from the Landsat Multispectral Scanners. Landsat imagery helps scientists track city growth in urban heat island studies.


Links to larger 640x605-pixel, 52K GIF. Credit: NASA and University of Georgia


Landsat 7 will also help scientists look into the past so we can chart the future better.

Left: Landsat images help reveal an ancient causeway (faint diagonal line) and temples (white dots) at Mirador, Guatemala. Credit: NASA

"Landsat 7 will be used with other remote sensing techniques to address issues in Mayan archeology and to monitor the effects of increasing deforestation in the area," said NASA archaeologist Tom Sever.The Peten, northern Guatemala, was inhabited by a population of several million Maya before their collapse in the 9th century A.D. The seventh and eight centuries were a time of crowning glory for millions of Maya; by 930 A.D. only a few scattered houses remained, testifying to one of the greatest disasters in human history. What is known is that at the time of their collapse the Maya had cut down most of their trees.


Web Links
NASA Earth Science Enterprise captures the spirit of exploration and focuses it on our own plan
The Landsat home page includes information on the mission and the satellite.
Cities Getting Ready for Next Heat Wave - Results applied from Urban Heat Island Pilot Project. Nov 20, 1998 story.
Project ATLANTA home page includes technical details on the study, including a description of the ATLAS sensor.
Remote sensing archaeology research at NASA.
After centuries of regeneration the Peten now represent the largest remaining tropical forest in Central America but is experiencing rapid deforestation in the wake of an invasion of settlers. The successful adaptive techniques of the indigenous population are being abandoned in favor of the destructive techniques of monoculture - raising a single crop - and cattle raising.

"Already, images from earlier Landsats have helped us track the loss of rain forests to farmers and loggers," Sever said. "It has also helped us recover several archaeological sites. Landsat 7's enhanced capabilities will be of great benefit to our efforts to answer questions about the past in order to protect the resources of the future."


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Other Earth-science satellite launches for 1999
  • May: GOES-L will be the 12th Geostationary Operational Environmental Satellite. Its cameras watch half the globe, giving scientists a broad view of developing weather.
  • May: QuikSCAT is a quick flight of the backup for the wind scatterometer instrument lost when Japan's Midori satellite failed in late 1997. The scatterometer measures microwave energy reflected back to the satellite to determine wave height.
  • July: Terra is the flagship of the Earth Observing System, a series of spacecraft that represent the next landmark steps in NASA's leadership role to observe the Earth from the unique vantage point of space. Focused on key measurements identified by a consensus of U.S. and international scientists, Terra will enable new research into the ways that Earth's land, oceans, air, ice, and life function as a total environmental system.
  • September: Shuttle Radar Topography Mission (carried on the STS-99 Space Shuttle mission) is an international project spearheaded by the National Imagery and Mapping Agency and NASA, with participation of the German Aerospace Center DLR. This radar system will gather data that will result in the most accurate and complete topographic map of the Earth's surface that has ever been assembled.
  • October: The Active Cavity Radiometer Irradiance Monitor will measure Total Solar Irradiance (TSI), the dominant source of energy in Earth's climate. The ACRIM III instrument is third in a series of long-term solar-monitoring tools extending back to 1980.
  • December: NOAA-L continues a series of NOAA Polar Operational Environmental Satellites (POES) started in the spring of 1998 with the launch of NOAA-K. Operating at lower altitude than the GOES series, the NOAA series satellites trade the global view for twice-daily close-ups of most spots on Earth
  • December: Earth Observing-1 is the front runner satellite in NASA's New Millennium Program Earth Observing to develop and validate instruments and technologies for space-based Earth observations with new, unique spatial, spectral and temporal characteristics.


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Author: Dave Dooling
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NASA Official: Ron Koczor