Part 3—Zoom In for a Closer Look

Step 1 – Reduce the Time Frame of the Graph from Two Years to One

Most of the graphs in Part 2 showed data across a two-year time frame. This was helpful for looking at patterns that repeat on an annual cycle. In this part of the challenge you will use various date features to zoom in for a more detailed look at the data sets and the relationships that exist among them.

  1. Use the Plot Date Range slider function and type-in selection boxes to set the date range for the just the year 1999. (1999-01-01 to 1999-12-31)

  2. Some patterns should now be easier to see, and you'll be able to get a better sense of what the year was like. Examine the image while considering the following questions:
    • At approximately what date in 1999 did the maximum air temperature start to regularly reach above 12 degrees C?
    • At approximately what date in 1999 did the maximum air temperature start to frequently rise above 30 degrees C?
    • At approximately what date did the soil moisture at 10 cm first drop below .22 g/g?
    • At approximately what date did the soil moisture at 90 cm first drop below .22 g/g?

Step 2 – Change the Time Frame to Limit the Graph to January, February, and March, 1999

Reduce the time frame again to include only the months of January, February, and March.

  1. Change the ending month from December (=12) to March (=03). To achieve this you can either use the type-in dialog boxes, or the calendar function, to make these changes.
  2. Plot the graph.
  3. Use the printer icon, located in the upper-right corner of the graph image, to print it and save it for use in the last step.

  4. Examine the image while considering the following questions.
    • On approximately how many days does the maximum air temperature get above freezing?
    • During this three-month period, how much change do you notice in the soil moisture content at a depth of 10 cm below the surface? At 90 cm below the surface?

Step 3 – Change the Time Frame to Limit the Graph to April, May, and June, 1999

Reduce the time frame again to include only the months of April, May, and June 1999

  1. Change the starting month to April (=04) and the ending Month to June (=06); change the ending day from 30 to 31.
  2. Plot the graph.
  3. Use the printer icon, located in the upper-right corner of the graph image, to print it and save it for use in the last step.


  4. Examine the image while considering the following questions.
    • Between the end of April and approximately May 19, describe what happens to soil moisture content at 10 cm. Look at the rainfall pattern between April 25 and May 19. Does this help explain the change in soil moisture at 10 cm?
    • On approximately May 19 and again on May 22 there is a sharp rise in soil moisture content at 10 cm. Why do you think this happened?
    • What happens to the soil moisture content at 90 cm during the second half of June? How do you explain this change?
    • In addition to the data in the graph, can you think of any other natural changes that happen in the northern US during this time that might help explain the decrease in soil moisture content?

Step 4 – Change the Time Frame to Limit the Graph to July, August, and September, 1999

  1. Reduce the time frame again to select only the months of July, August, and September 1999
  2. Plot the graph.
  3. Print it and save it for use in the last step.


  4. Examine the image while considering the following questions.
    • What patterns or trends do you see in the Maximum Temperature across these three months? How do they compare with the maximum temperature patterns or trends where you live?
    • For a period of almost two weeks in July, no soil moisture data was collected. What assumption would you make about the soil moisture at 10 cm during that period of time, and what would be the basis of that assumption?
    • During late July (and possibly for most of July), soil moisture at 10 cm is quite steady, when compared to the changes that occur throughout much of August. How would you explain this?

Step 5 – Change the Time Frame to Limit the Graph to October, November, and December, 1999

  1. Reduce the time frame again to select only the months of October, November, and December 1999
  2. Plot the graph.
  3. Print it and save it for use in the last step.
  4. Examine the image above while considering the following question.
    • Compare the graph for the last three months of 1999 with the graph for the first three months of 1999. In what ways are they similar? In what ways do they differ?

Step 6 – Connect the Three-Month Graphs to Construct a Large Full-Year Graph

Trim the print-outs of the graphs so that they don't overlap, and tape them together to create a single, long graph that shows all of 1999. Then, compare this 4-sheet graph with the graph that shows all of 1999 on a single sheet.


Examine the image while considering the following questions.

  • Do the two graphs give you different impressions? Is having both better than having just one or the other?
  • Use one or both graphs to help you write a summary of how Maximum Air Temperature, Soil Moisture at 10 and 90 cm, and Rainfall vary across the year in Greenville, PA, and how they influence one another.

Once data is available in graphic form, aspects of Earth's complex system can start to become more obvious; patterns and relationships that may be difficult to notice without the graphs will start to emerge. For example, one might have guessed that soil moisture was greater in months when more rain occurred, which are the warmer months for Greenville, PA. Having the data makes it clear that soil moisture is actually greater in the cold months.

In Greenville, the natural vegetation is less active or dormant in the winter. Deciduous trees lose their leaves. The ground freezes and can become covered with snow or ice. There is less solar energy. In the warmer months, there are three natural changes that can reduce soil moisture. Increased solar energy thaws the soil and at some point causes evaporation. Trees and other vegetation become active, draw water out of the soil, and release it into the air. This is called transpiration. Finally, wind can increase both evaporation and transpiration.