Part 2—Select NEO Data and Explore NEO Interface

Step 1 – Select and Display a Map of the NEO Dataset Aerosol Optical Thickness (AOT)

Go to the NASA Earth Observations (NEO) homepage . The NEO website will open in a new browser window. Be sure to use a Web browser that is both Flash and Java enabled. NEO organizes datasets into five categories: Ocean, Atmosphere, Energy, Land, and Life.

Step 2 – Access and Learn about Aerosol Optical Thickness Data

  1. Click the Atmosphere tab just below the image. Locate the Aerosol Optical Thickness (MODIS) dataset in the list and select it.

  2. Click View to be sure you are displaying the map for the date you wish.

  3. Each of these images represents a "composite" picture that shows the "monthly average" measurements of aerosol concentration. What does this mean?

    Satellites that go over the poles in their orbits aren't far enough away from Earth to take a picture of the whole planet at one time. Instead, they take measurements of the part of the planet that is directly beneath them on each orbit. Measurements are made along a strip centered on satellites' ground tracks. Scientists take the measurements from all the individual ground tracks or swaths and digitally stitch them together into one composite image. This way, we can see measurements for the whole Earth at once. In this case, measurements taken over an entire month are used to make the image. For locations that the satellite passed over more than once during the month, all the values for each location are averaged.
  4. Notice the color legend below the Aerosol Optical Thickness image. Examine it to understand what the colors on the map mean. Areas where no measurements were taken are shown in black.
    • Where in the world do you see the highest values?
    • What areas have the lowest values?
    • What do you know about those areas?
    • Why do you think these areas have high or low values?
  5. To learn more about the Aerosol Optical Thickness dataset, click the About this dataset link to the left of the color bar.
  6. Note the different levels of information about the dataset. Use the Less Detail | More Detail links or the short, medium, and long page icons to toggle between less complex and more complex explanations.

  7. Find the answers to the following questions within the description.
    • What are aerosols? What are they composed of?
    • What are the major sources of aerosols?
    • Are aerosols evenly distributed throughout the atmosphere? If not, why not?
    • Why is it important for scientists and policy makers to understand the role of particulates in the atmosphere?
    • What NASA instrument (sensor) gathers information on aerosols? What does the sensor measure in the atmosphere to determine the amount of aerosols?
    • The MODIS instrument is the aerosol optical thickness sensor. It measures how much light is prevented from reaching Earth. The values range from 0 to 1. So low numbers like 0.1 allow most light through, and a 1 allows no light. Aerosols are tiny solid or liquid particles, which can be dust, smoke, seasalts, factory or car pollution. These particles affect visibility, human health, and climate change. Aerosols are from constant sources like cars in cities or erratic sources like a volcanic eruption or forest fire.

  8. Close the description window when done.

Step 3 – Explore the NEO Map Interface Buttons and Tools

  1. Examine the homepage (Blue Marble) image and learn how to navigate the View. The top three buttons in the upper left allow you to control your view of the image. Click the ? button to find out how the buttons and tools work. Then use them to zoom in on a place that you know. When you click the ? button, you get a pop-up box with all the buttons and tools described. Click the X in the upper right-hand corner to close the Map Widget Help box.

    1. Click the + button to zoom in the View.
    2. Use the Drag tool to pan (move) around.
    3. When you are done, use the - button to zoom out or the = button to zoom to the full extent of the View.

  2. Zoom in on a place you recognize. Look for your school, a near-by lake, or other features you know.
  3. This limitation of not being able to see many details in the image demonstrates the concept of an image's spatial resolution. Each picture element or pixel in the image represents a square area on Earth's surface that is 11 km on each side in this particular image. This is a relatively low spatial resolution image.

Step 4 – Download a Year of Monthly AOT Data

Temporal resolution is a term that describes the time interval of the data. These aerosol data have been averaged over different time periods, so the user has a choice of monthly, 8 day, or 1 day averages. Monthly is a good choice for an overview of a year's patterns. Daily images might be better to view an intermittent event at high resolution, like the spread of a wildfire.
  1. Before you begin, create a folder named AOT2008 to hold the twelve images you will download.
  2. Open the NASA Earth Observations (NEO) homepage .
  3. In the list of Atmosphere datasets, click Aerosol Optical Thickness. This will display the most recent Aerosol Optical Thickness image in the main window, and list available data sets in the Search Results window.
  4. Use Next to find and download the January 1, 2008 to January 31, 2008 image at a resolution of 0.5 degrees and save it as 01_aot2008.jpg. Repeat the process for all twelve months of 2008 until you end up with a total of twelve images, named from 01_ aot2008.jpg to 12_ aot2008.jpg.
    1. Use Next to find the January 1, 2008 to January 31, 2008 dataset and use + and View to display the image. In the Download Options box, change the selection from Full to Resize. Then select a fixed resolution of 0.5 degrees. Click the Get Image button to render the image.

    2. The rendered image opens in a new window. On a PC, right-click on the image and on a Mac, control-click on the image to download and save it. Do not change the file format, keeping the image as a jpeg. Save the image into the AOT2008 folder you created and name it 01_aot2008.jpg.(That's a zero, 1, underscore, etc "01_")

    3. Click the "+ and then View to display the February 1, 2008 to February 28, 2008 image. Use the same procedure as above to Resize, Get Image and save the rendered image with a fixed resolution of 0.5 degrees.
    4. Save the second image, naming it 02_aot2008.jpg in the AOT2008 folder.
    5. Use the Prev button at the bottom of the Search Results to access the remaining months from 2008. You should end up with a total of twelve images, named from 01_ aot2008.jpg to 12_ aot2008.jpg.
  5. You need all 12 images to perform the Part 3, "animation". If you had difficulty obtaining the images from NEO, then download and save the ones here below into your AOT2008 folder. Click the thumbnail to open the full size image in a larger window. Then right-click (or control-click 1-button Mac) to choose file Save Image As... Do not rename the files. Keep them as 01_aot2008.jpg, 02_aot2008.jpg, etc.

  6. Jan 2008 AOT image January 2008

    Feb AOT 2008 February 2008

    Mar AOT 2008 March 2008

    April AOT 2008 April 2008

    Apr AOT 2008 May 2008

    June AOT 2008 June 2008

    July AOT 2008 July 2008

    Aug AOT 2008 August 2008

    Sept AOT 2008 September 2008

    Oct AOT 2008 October 2008

    Nov AOT 2008 November 2008

    Dec AOT 2008 December 2008

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