Part 2—Explore Population and NO2 Concentrations across the U.S.

Step 1 Add Data Files and Set Navigation Controls

  1. If necessary, launch Google Earth by double-clicking its icon or selecting it from the programs list in the Start menu (PC).
  2. Check that these three files are listed in your Google Earth Temporary Places list:
    • Population Density
    • EOS-Aura-OMI-L3-2010_01_NO2TropCS30.kml - (January 2010 Aura NO2 file)
    • EOS-Aura-OMI-L3-2010_05_NO2TropCS30.kml - (May 2010 Aura NO2 file)
    1. Choose File > Open...

    2. Browse to where you saved the High-Res World Population Density file. (Note: in this case it was given a file name 37291.kmz when it was downloaded; your file name may be different.)
    3. Select the file and click Open.

    4. Do the same for the two Aura data files.

    If you were unable to download the data files to use in this chapter, use this completed and saved Google Earth project file. Aura NO2 and Population.kmz (KMZ File 1014kB Nov15 11) Right-click on the file name and choose either "Save Link As..." (Mac) or Save target As... (PC) to download the file to your Documents folder or Desktop.

  3. Make sure that Google Earth's navigation controls are available by choosing View > Show Navigation and selecting Always.
  4. Use the navigation controls to view North America and zoom in so it almost fills your screen.

    Slide the zoom function slider upward to zoom in on an area.

Step 2 Explore the Population Density Data

  1. In Google Earth, deselect the checkboxes for the two NO2 datasets to turn them off.
  2. In your list of Places, click the Population Density data layer to activate it. When you do this its name will be highlighted in the list.
  3. Adjust the transparency bar slider to see how you can see some of the features of the land through the population colors.
  4. Use the legend at right to understand what the population image is showing. Note: there is also a similar legend in the layer.
    • Which color on the map shows the most crowded places?

      Dark brown. The darker the color in the Population data layer, the greater the number of people living within each square kilometer.

      Notice the dark brown color for Chicago, Denver, and Minneapolis indicating a high population density.

    • From the map, which region of the contiguous U.S. has the highest population density?
      Population is greatest in the northeast and throughout the eastern half of the country.

Step 3 Explore the NO2 Concentration Data for January

  1. Deselect the Population Density layer, then select (turn-on) the January 2010 NO2 data layer, the one with the date of _2010_01_ in its title.

  2. The image above is the color scale for the Aura NO2 data images. Look at the images of NO2 and answer the following questions:
    • Which colors indicate relatively high nitrogen dioxide concentrations?

      Yellow, orange and red indicate relatively high concentrations, while green and blue indicate relatively low levels of NO2.

    • Which region of the contiguous U.S. has the highest concentrations of NO2?
      The eastern half of the United States has noticeably greater NO2 concentrations than the western half.
  3. Adjust the transparency bar for the January 2010 NO2 data layer so that you can see some of the features of the land through the colors.

Step 4 Seasonal Effect on NO2 Concentration

  1. Leave the January 2010 NO2 data layer on and check the May 2010 NO2 data layer to turn it on as well.
    Image CC
  2. Use the transparency slider to look for differences in the two data layers. You can also examine the differences between January and May by repeatedly turning the top one in the list on and off to "flip" between them.
    • What differences do you observe in NO2 concentrations between May and January in the eastern half of the country?
      The eastern half of the United States had greater NO2 concentrations in January 2010 than in May 2010 in these two images shown below.

      January 2010.

      May 2010.

    • Hypothesize one or more possible explanations for the difference you observed.
      • People in the east use more electric heaters and furnaces in January than they do in May. The greater NO2 concentrations in January might be produced through direct burning of natural gas in furnaces and the burning of coal at power plants.
      • More people in the east ride their bikes in May than in January. The lower NO2 concentrations in May could be from fewer people driving their cars.

Step 5 Explore the Relationship between NO2 Concentration and Population

  1. Deselect all layers except the Population Density layer. Slide the transparency bar all the way to the right to make that layer fully opaque (not transparent).
  2. Keep the Population Density layer on and also turn on the January 2010 NO2 data layer. Use the transparency slider and "flipping" technique to see how the two parameters are related.

    Because the population density and the NO2 concentration layers both use dark colors for high values, it may be difficult to see the data in both images at once. You may want to slide the transparency bar slowly all the way to the left and then back to the right.

    Another option is to activate the January 2010 data layer and adjust its transparency so that you can see the Population Density layer through it.

  3. Based on your observations, describe the relationship between population density and NO2 concentration.
    Areas with a higher population densities have higher NO2 concentrations.

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