Changing Global Land Surface
 

Terra and Landsat-7 Land Surface Observations
The extent, type, and health of global vegetation will be a key factor in determining the continental climates and the rate of increase of atmospheric carbon dioxide in the near future. To understand the important processes affected by vegetation and how these processes will influence the future state of the Earth, we need to develop improved predictive computer simulation models of the Earth's climate and biosphere. To make these models work realistically we need to know more about the distribution and season changes of the world's vegetation, as well as the exchanges of water and carbon between land vegetation and the atmosphere. The only practical way to do this consistently, continuously, and globally is through satellite remote sensing. Satellite instruments have already been used to detect changes in photosynthetic capacity, vegetation type, and growing season dynamics.

Brazilian Deforestation
Figure 3: Satellite image of deforestation in the Amazon region, taken from the Brazilian state of Para on July 15, 1986. The dark areas are forest, the white is deforested areas, and the gray is re-growth. The pattern of deforestation spreading along roads is obvious in the lower half of the image. Scattered larger clearings can be seen near the center of the image.

Terra and Landsat-7 will provide scientists with powerful tools for monitoring the Earth's biosphere. Terra instruments such as the Moderate-resolution Imaging Spectroradiometer (MODIS) and the Multi-angle Imaging Spectroradiometer (MISR) will provide continuous global coverage, permitting a thorough study of seasonal and inter-annual changes in land vegetation. The high-resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER, aboard Terra) and Enhanced Thematic Mapper (ETM+, aboard Landsat-7) instruments will provide detailed information about selected areas of special interest around the world; for example, areas undergoing intense deforestation (Figure 3). Using the data from these instruments, scientists will use computer models to study the effects of a changing climate on global vegetation and the Earth's biosphere.

Retreat of Muir Glacier
Figure 4: These Landsat images, acquired 13 years apart, show the retreat of the Muir Glacier (arrow) in southeastern Alaska. Between Sep 12, 1973 and Sep 6, 1986, the Muir Glacier retreated to the northwest more than 7 km.

The MODIS and MISR instruments on the Terra satellite will provide global monitoring of snow and ice extent, while the ASTER and ETM+ instruments will yield high-resolution images of snow and ice boundaries and glacier retreat sites (Figure 4). ASTER and ETM+ will also enable us to monitor inland waters, lakes, rivers and floodplains. (Hydrologists and meteorologists currently do not have access to global flood data.) Similarly, changes in the world's coastal zones and coral reefs will be monitored with these high-resolution instruments.

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Changing Global Land Surface
Introduction
The Carbon Cycle
Greenhouse Warming
Plants, Snow & Ice
Terra & Landsat Observations
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