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  Activity #11
Comparing Vegetation to Landcover Classification (Jan 1998–Dec 1998)

In this activity, you can view the Earth from the unique perspective of outer space. You will examine monthly snapshots (or global datasets) of our planet’s surface and atmosphere. During this activity, you will investigate complex interactions of the Earth’s lands and life by looking for patterns and changes over time in the planet’s vegetation productivity as a function of landcover. You will make connections to global environmental issues.

 
Vegetation palette   Landcover palette

 

The animation will play through once automatically. To replay, click the play button. To step through frames individually, use the left and right arrows on the bottom right corner of the animation box or the left and right arrows on the keyboard.

Background:
To measure and map the density of green vegetation across the Earth’s landscapes, scientists use satellite sensors that observe the distinct wavelengths of visible and near-infrared sunlight that is absorbed and reflected by the plants. Calculating the ratio of the visible and near-infrared light reflected back up to the sensor yields a number from minus one (-1) to plus one (+1). The result of this calculation is called the Normalized Difference Vegetation Index, or NDVI. An NDVI value of zero means no green vegetation and close to +1 (0.8 - 0.9) indicates the highest possible density of green leaves.

Scientists now have a modified green vegetation data set called FASIR NDVI. In short, FASIR NDVI is a highly corrected global data set composited into one-month time periods. Scientists removed a variety of erroneous artifacts from the data, ranging from sensor degradation, to volcanic aerosol effects, cloud contamination, short-term atmospheric effects (e.g., water vapor and aerosol effects), sun angle variations, and missing data. These data were collected from January 1982 through December 1990 by the Advanced Very High Resolution Radiometer (AVHRR) flying aboard NOAA-7, NOAA-9, and NOAA-11 satellites. (“FASIR” stands for Fourier-Adjusted, Solar-zenith-angle corrected, Interpolated, Reconstructed data.)

Landcover classification is a description of the type of vegetation growing in an area. Different types of plants (e.g., grasses versus pine trees) reflect uniquely, giving a 'spectral signature'. Scientists use satellites to detect the spectral signature of vegetation and produce landcover classification maps from the data. Landcover classification data has applications in urban planning, natural resources management, wildlife biology, and forestry. (Data produced by the University of Maryland)

Questions:

  1. As you carefully observe the animation, you see that the amount of green vegetation changes with the seasons. Notice that the changes in green vegetation are dramatic in the Northern Hemisphere. Use the landcover data sets to determine why there is a difference between the two hemispheres.
     
     

Links:

  1. Measuring Vegetation (http://Earthobservatory.nasa.gov/Library/MeasuringVegetation/)
     
  2. Modeling Earth’s Land Biosphere (http://Earthobservatory.nasa.gov/Study/Modeling/biosphere_modeling.html)
     
  3. Growing Data (http://Earthobservatory.nasa.gov/Study/GrowingData/)
     
  4. Mission: Biomes http://earthobservatory.nasa.gov(/Laboratory/Biome/)
     

next activity (#12): Comparing UV radiation exposure to ozone during the month of October 2000
previous activity (#10): Comparing 4 Km2 fires during the month of August 1999 to fires in the month of February 2000

   
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