Part 5—Analyze Relationships Between Datasets

Step 1 – Select Three Maps for Analysis

Select the April 2009 Reflected Shortwave Radiation Map for Analysis

  1. Go to the NASA Earth Observations (NEO) website and display the Energy Dataset, Reflected Shortwave Radiation image for April 1, 2009 to April 30, 2009. Click on the Energy tab under the map to display the Energy Datasets. Then select the Reflected Shortwave Radiation dataset.
  2. In the Search Results section, select the the April 1 to April 30, 2009 image for analysis by clicking the appropriate "+" button to expand its field. Click View to display the image.
  3. AnalysisBox with Albedo Click Analyze this image to add it to the Analysis box.

    2 analyse this image albedo
  4. You should now see one image listed in the Analysis box.
  5. If you wish to change one or more of your selections for analysis, click Remove just below the item you want to deselect, and then go back to the Search Results section to find the map you want to add.

Select the April 2009 Snow Cover Map for Analysis

  1. To select another image for analysis, click on the Land tab under the map to display the Land Datasets. Then select the Snow Cover (MODIS) dataset.
  2. AnalysisBox with Albedo and Snow In the Search Results section, select the April 1 to May 1, 2009 image for analysis by clicking the appropriate "+" button to expand its field. Click View to display the image.
  3. Click Analyze this image to add it to the Analysis box.
    snow cover analyze image
  4. You should now have two images in the Analysis box.

Select the April 2009 Land Surface Temperature Map for Analysis

  1. To select another image for analysis, click on the Land tab under the map to display the Land Datasets. Then select the Land Surface Temperature (Day) (MODIS) dataset.

  2. analysis box filled In the Search Results section, select the the April 1 to April 30, 2009 image for analysis by clicking the appropriate "+" button to expand its field. Click View to display the image.


  3. Click Analyze this image to add it to the Analysis box.
    6 analyse this image land surface temp
  4. There should now be three images listed in the Analysis box.

Step 2 – Launch and Configure Analysis

Once the three images of reflected shortwave radiation, snow cover, and land surface temperature are in the Analysis box, it becomes possible to analyze the relationship between these variables.
  1. From the Analysis box where the three images are listed, Click configure/launch analysis. A new Analysis window will open.
  2. Click the Select Area tab. Use the Pointer tool (in the upper-left hand corner) to click and drag a box in the map around North America and Greenland. Click Select to save your region of interest.
    1. Click the Select Area tab.
      select are opening screen
    2. Click and Drag to select the area. Then click the blue Select button. You will get a message that your selection has been saved.
      select area in configure analysis

Step 3 – Animate the Maps or Step Through Them

  1. Click the Mode tab. In this window, select animation. Then click Launch analysis at the bottom of this window. A new window will open. The new window is the Image Composite Explorer or ICE tool.
  2. In the new window, the three images that were selected appear as thumbnails across the top. Click the Step button to the right of the large map to move through the animation, frame by frame. Observe the relationships between the three images.

Step 4 – Plot a Transect South to North

How do reflected shortwave radiation, snow cover, and temperature change as one moves north across a continent? The Plot transect button in NEO allows one to simultaneously visually and graphically explore this relationship.

  1. While still in the Analysis window, prepare the images for analysis. In order to be able to see familiar landmarks, use the Step button to move through the images so that the Land Surface Temperature image is the one that is in view.
  2. Click the Plot transect button.
  3. Click and drag from South to North on the map. Experiment with different areas. Notice that as you move the cursor, a graph is generated.
  4. Click and drag the cursor from Texas to the area in Canada just to the left (West) of Hudson Bay in Canada.
    South to North transect annotated small
  5. Observe the relationship between the three variables in the plotted graph. Summarize these relationships.
    As reflected shortwave radiation increases, so does snow cover. Conversely, as reflected shortwave radiation and snow cover increase, land surface temperature drops. While there are areas where this may not be absolute, the relationship between the three is solid.

Step 5 – Plot a Transect West to East

In order to emphasize the relationship between snow cover and reflected shortwave radiation are independent of latitude, plot a transect from West to East. In this case it is best to have Snow Cover as the top image.
  1. Use the Step button to move through the images so that the Snow Cover image is in view.
  2. Click and drag another transect, this time from West to East, in a snow covered area of Canada.
  3. What is the relationship between the extent of Snow Cover and Reflected Shortwave Radiation?
  4. While the second graph, comparing snow cover and reflected radiation, is a "noisier" graph, the two lines still move in concert. The more snow cover, the more reflected solar radiation. Snow has a very high albedo, especially clean white snow. Snow that is dirty from dust or soot, has a lower albedo, or ability to reflect shortwave radiation, and it actually absorbs sunlight which can cause increased melting.

Step 6 – Reflect on the Relationships

Scientists think of snow and ice cover similar to a mirror on the surface of the Earth. As global snow cover decreases due to global warming, it is likely that the Earth's temperatures will also increase, triggering further changes in snow cover. This is what is known as a positive feedback loopFeedback Loop Snow Ice Albedo . The consequences of decreasing snow cover include negative impacts on the both the human and animal populations of the Arctic regions. One way humans are affected is through reduced runoff from snow melt. This runoff often provides much needed water for drinking and agriculture. Furthermore, decreases in snow cover, may lead to less opportunities for winter recreation, such as skiing.

In the animal environment, the impacts are even more threatening. Decreases in snow cover negatively impact many of the animals of the Arctic including musk ox, reindeer, vole, and lemming. All of these animals have adapted to the winter habitat. The smaller animals such as lemmings and voles depend on snow to provide them with food storage locations, habitat for burrowing and critical insulation. As the population of these species declines, it can trigger a cascading impact throughout the entire delicate Arctic food web.

So while a possible decrease in severe and dangerous winter storms may be a benefit for some of the inhabitants of Northern climates, overall, the changes in the "ways of winter" will likely be negative for the Earth systems as we know them. To learn more about changes predicted for Global snow cover, read the full report on the Global Outlook for Ice and Snow from the United Nations Environment Programme.


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