Case Study: Colorado Ozone July 29, 2014


Students learn that ozone varies through the hours of the day and over geographic area depending on the amount of pollution, sunlight, topography, and weather.




  • Note that this case study assumes prior learning about ground-level ozone formation. Dive into this case study once students have completed the Introduction to Air Pollution and Ozone sections of this teaching box.
  • Explain that a field campaign is a large project to collect data which involves many people - sometimes hundreds. During a field campaign researchers work together to collect many different types of data from the same place. Tell students that in this activity they will explore some of the data that was collected during air pollution field campaigns that happened in the Colorado Front Range during the summer of 2014.
  • Have students watch short videos that introduce the FRAPPE and NASA DISCOVER AQ Field Campaigns.

Part 1: Investigate ozone pollution at one location over time.


  • Provide student pairs Student Sheet 1A, a graph of ozone at Chatfield on July 29, 2014, and ask students to identify, on the graph, times:
    • When ozone levels are low
    • When ozone levels increase steadily
    • When ozone exceeds safe levels (over 75 ppb)
    • When ozone levels drop quickly

Interpret observations:

  1. Ask students what they think caused the ozone levels to increase and decrease during a day. Why is ozone low at night? Why does the ozone grow in the morning? Why does it drop quickly at 1:30?
  2. Remind students of the process of ozone formation that they investigated previously. For ozone to grow there needs to be NOx pollution and sunlight. It can grow during the day while the Sun is shining and pollution is accumulating. Ask students what else can impact ozone.
  3. Provide student pairs with Student Sheet 1B and show the weather radar from July 29, 2014.
  4. Ask students if they see any correlation between the weather and the ozone levels (students should notice that ozone starts to climb after sunrise and that afternoon thunderstorms caused ozone to drop in the afternoon.)

Part 2: Compare ozone pollution at three locations.


  • With Student Sheet 2A and Student Sheet 1Ahave students compare the graphs of ozone from three locations (Denver, Aspen Park, and Chatfield) and discuss similarities and differences. Remind students that all three graphs show ozone over the same day, July 29, 2014. Ask students whether all three locations had ozone over safe levels (75 ppb). Students should notice that only Chatfield had levels that high.

Interpret observations:

  1. As a class, brainstorm what could cause ozone to be higher in one area that another. Why is Aspen Park less than Chatfield? Why is Denver less than Chatfield?
  2. Have students investigate the role of topography and wind. Provide students with Student Sheet 2B (area topo map) so that they can see the geographic differences in these three locations. Have students note the wind directions that they reviewed in Part 1 on the map of the three locations. (Aspen Park in in the mountains, above the ozone. Ozone levels in Chatfield are higher than Denver because wind blew ozone, allowing it to pool at the base of the mountains.)