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TEACHERS: Tracking Ozone

In this lesson, students will track the ozone levels over a seven day period, in which an "Ozone Event" has occurred. The students will also track the average weather conditions for the seven day period and create final conclusions about the affect of weather on the formation of ground level ozone.

Students will be able to:
  • track an ozone event in Groton, CT
  • compare weather changes and the subsequent ozone levels
  • make comparisons and determinations about ozone levels
  • utilizing graphing skills




There are several factors involved with the formation of ground level ozone, including:

  • Sunlight/Ultraviolet Radiation: Ground level ozone is produced by a photochemical reaction. A photochemical reaction is a chemical reaction that requires light (in this case sunlight) to provide the energy for the reaction to proceed. During the summer months, the earth is tilted in such a way that the sun's rays are more direct, and more intense. This combination creates longer and warmer days than in the winter months. Ground level ozone is called the "summertime pollutant" because that is the time of year when the energy from the sun is intense enough to trigger the photochemical reaction necessary to produce ground level ozone from NOx and VOCs.
  • Cloud Cover: Cloudless skies create conditions for warmer days to occur. But keep in mind that a completely cloudless sky is not necessary for the photochemical process to start.  The more sunlight available, the more likely the ground level ozone photochemical reaction will occur.
  • Temperature: High temperatures can increase ozone levels by increasing the rate at which the chemical reaction described above occurs.
  • Wind Direction: NOx can travel large distances before reacting to form ozone. For that reason, it creates regional pollution problems, rather than simply affecting the local area where it is emitted. The action of pollutants traveling distances is called transport. Transported pollutants contribute significantly to the presence of ground level ozone in rural areas.
  • Wind Speed: Low wind speeds (less than about 10 mph) are necessary for the accumulation of pollutants and subsequent formation of high concentrations of ozone. At speeds above about 10 mph, pollutants are diluted too rapidly for ozone to accumulate significantly.
  • Volatile Organic Compounds (VOC's): Emissions from human activities include driving, industrial manufacturing, lawn mowing and painting are all sources of hydrocarbons. VOC's are one of the necessary ingredients to the ozone equation.
  • Oxides of Nitrogen (NOx): Nitrogen oxides (NOx), the other chemical precursor of ozone, are produced whenever fossil fuels are burned and are primarily produced by motor vehicles and power plants.

The photochemical reaction that produces ground level ozone requires several factors to be present and tends to occur when a stagnant air mass develops during hot and sunny conditions. The air will not become stagnant if weather systems continue to move through the area and displace the air with cleaner, "fresher" air.



PART 1: Gather the Data
  1. Working as a group, collect the ozone data for Hartford, CT for August 4 - 11, 2001. Note: Scroll down to the 8 Hour Average Peak Concentration image.
    August 4 August 5 August 6 August 7
    August 8 August 9 August 10 August 11

  2. Determine the AQI Color, Air Quality, and Maximum AQI Value for all seven days and enter the data into the table on the Student Worksheet (the first date has already been completed for you).
    • NOTE: To determine the AQI Average value, find the average between the two numbers of the AQI range.  For example, Green has a range of 0 50, with an average, of 25.
  3. In another browser window, or another computer, access the Weather Underground site, and collect the weather information for Hartford, CT . For this lesson, gather the Maximum Temperature, the Wind Speed, and Events for each of the seven days. This information is found in the smaller table at the top of the web page

    Dates and Location: August 4 - 11, 2001 for Hartford, CT

    Date AQI Color Air Quality Max. AQI Value AQI Ave. Value Max. Temp. Wind Speed Events
    August 4 Green Good 50 25 75 F 4 mph Rain
    August 5              
    August ...              

  4. Make the following three bar graphs using the data in your table. Ask your teacher for assistance if you are unsure how to make the graphs.
    1. Ozone v. Time
    2. Temperature v. Time
    3. Wind Speed v. Time

PART 2: Analyze the Data

  • After you have completed the graphs, use the data in the table and the graphs to answer the questions on the Student Worksheet.


  1. Have the students discuss their ideas. Describe the steps, or how would you go about predicting if there will be ground level ozone present in the next few days?


Implementation Tips
This lesson uses archived images, which will offer greater flexibility to prepare for the lesson if you expect network failure, or cannot get into the computer lab.

If there are not enough computers for students, you could:

  • create small working groups
  • project the images and weather data for the class using an LCD projector
  • have a group of students try the activity by just using the newspaper weather report and forecast
  • collaborate with Computer Teacher
  • arrange to take your class or small group of students to the Internet lab to access computers on a regular basis for data collection

If the network is slow or not working, you could:
  • print the images and weather data on overheads and use the overhead project to project the images for the class
  • print and/or photocopy the images and weather data, enough for small student working groups
  • have the students do the activity by just using the newspaper weather report and forecast
  • save data to disk

Please refer to the Graphing Tips and Examples for assistance.

Graphing Cloud Cover/Conditions (Sunlight) - optional
This graph is optional and increases the complexity of the lesson. To graph Cloud Cover versus Time, use the chart below. The chart lists various sky conditions (terminology may be subjective) with a numerical value associated with each condition to ease the students' ability to graph the data.

The Cloud Cover data, gathered from the Weather Underground site, specifically, the "Conditions" column, refers to the Cloud Cover visible in the sky. Cloud Cover is often judged by the scale below and expressed in one of four terms, Clear, Scattered, Broken, and Overcast. For graphing purposes, the terms need to be expressed with a numerical value. In addition to explaining the conversion to your students, it may be necessary to point out that the amount of cloud cover has a direct relationship with the amount of sunlight, and the amount of sunlight has a relationship with the amount of ground level ozone generated during the day.
Cloud Cover/Conditions % Cloud Cover
Clear 0% > 10%
Scattered (includes Partly Cloudy) 10% - 50%
Broken (includes Mostly Cloudy) 50% - 90%
Overcast 90% +


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