Changing Ozone Levels in the Earth's Atmosphere By Tony Marcino, Bill Miller, and Jo Ann Mulvany ABSTRACT Topics such as "Ozone Hole," chlorofluorocarbons, skin cancer, global warming, and ozone depletion have become modern day buzz words. Recent focus on the Antarctic "ozone hole" has generated a need for students to examine ozone data so that they can evaluate the nature of changing ozone levels. Examination of this data will allow students to make wiser decisions concerning the use and misuse of the environment. This activity uses data on ozone concentration gathered by the TOMS sensor on the Nimbus 7 satellite. In doing this exercise students will: access data from the JEdI B disc, plot the data on a latitude longitude grid supplied with the activity, draw isolines through the gridded data, and then practice on a sample exercise. Subsequently, students will work in groups to explore the data base and develop a model depicting global concentrations of ozone. Title: Changing Ozone Levels in the Earth's Atmosphere 2061 Theme: Change, Patterns of Change, Scale Major Concepts: Change, Patterns of Change, Global Change, Mapping, Computations Process: Mapping models, Computations, Cooperative learning, Data analysis Attitudes: Global awareness, Demand for verification, Respect for data Disciplines:Geography, Mathematics, Science Grade Level:Middle School-High School Key Word Search: BACKGROUND INFORMATION NASA has been measuring ozone from space for more than 10 years using an instrument called TOMS (Total Ozone Mapping Spectrometer). TOMS is on the Nimbus 7 satellite which is in a south-north polar orbit so that it is always close to local noon/midnight beneath the satellite. TOMS measures ozone by measuring the ultraviolet sunlight scattered from the Earth's atmosphere. Since ozone absorbs the ultraviolet light (protecting us from sunburn), the more ozone that is present, the less scattered light TOMS will observe. Ozone is inferred from the ratio of two wavelengths, 312 nm (nanometers) and 331 nm for instance, where one wavelength is strongly absorbed by ozone while the other is only weakly absorbed. Atmospheric ozone is produced at the surface as a pollutant and by natural processes in the stratosphere. The TOMS instrument measures both, but the data are primarily a measure of stratospheric ozone since the surface ozone does not rise to the stratosphere. Ozone in the stratosphere is considered "good" because it protects us from sunburn. Ozone near the surface is considered "bad" because it damages the lungs. The JEdI B disc contains planetary ozone data for one day a year (October 7) for 10 years (1979 through l988). In addition the disc contains worldwide data for every day from September 1 through October 31 for l987 only. These data are recorded in Dobson units, defined as a milli-atmosphere-centimeter of ozone. Values between 300-400 Dobson units are considered average. When values fall below 250, ozone is considered low; high values exceed 400. The ozone values are printed in a table which lists the values within a specific region of the world. This region covers 11 degrees of latitude and 11.25 degrees of longitude and is centered around the latitude and longitude specified by the user. OBJECTIVES CONTENT: Students will analyze variations in global ozone levels and describe how those levels have changed over a 10 year period. PROCESS: Students will construct ozone level models and develop skills in data grid analysis through the application of basic computational skills. MATERIALS: JEdI CD-ROM B disc, mercator world map, colored pencils PROCEDURE Access the Data 1. Insert the JEdI B disc in the CD-ROM drive. With the C:\> prompt on your screen, type L: and hit [Enter]. 2. At the L:\> prompt type PROGRAMS\DOS\TOMS\DOCS\PROG and hit [Enter]. 3. At Main Menu Option type R and hit [Enter] to read the data Ozone Data for 87/10/07 - Washington, D.C. 1. At the date prompt type 87/10/07 [Enter] to designate the sample data date. 2. Type +39 -77 [Enter] to designate the center of the data grid area (Washington, DC) (+=north latitude, -=west longitude). Plotting the 87/10/07 - WASHINGTON, D.C., Data 1. Use the displayed data to complete the plotting of the Dobson unit data points on Figure 1 [F9]. 2. Designate Washington, DC, by drawing a star at the 39o N, 77o W on Figure 1 [F9]. 3. Complete drawing the isodob lines on Figure 1 [F9]. Assign a color for each Dobson interval band and shade accordingly. Lines connecting points of equal Dobson values are called isodobs. Several isodobs are drawn on Figure 1 at a 20 Dobson value interval. 4. Construct a legend showing Dobson value ranges and the color representing each range. Use an "H" to designate the area of highest value and an "L" to designate the area of lowest Dobson value. Ozone Data for 82/10/07 - Washington, D.C. 1. Now repeat the above procedures for Washington, DC, using October 7, 1982, and plot the data on Figure 2 [F9]. 2. Exit the 1987 data file by typing N [Enter]. 3. At the Main Menu, type R [Enter] to read more data files. 4. At the date prompt, type 82/10/07 [Enter]. 5. When asked for the coordinates, type +39 -77 [Enter]. 6. Record this data on Figure 2 [F9] and complete, using the same procedure used in developing Figure 1 [F9]. Ozone Data for 87/10/07 - Antarctica 1. Return to Main Menu and type the date 87/10/07 and the coordinates -85 +3. 2. Record this data on the Figure 3 [F9] grid. 3. The extent of the "ozone hole" can be examined by analyzing the data in Figures 1 and 2 [F9]. Ozone Data for 82/10/07 - Antarctica 1. Return to Main Menu and type the date 82/10/07 and the coordinates -85 +3. 2. Record this data on the Figure 4 [F9] grid. 3. The extent of the "ozone hole" can be examined by analyzing the data as directed above in Figures 1, 2, 3, and 4 [F9]. ANALYSIS Graph and Data Analysis 1. What is the lowest concentration of ozone in Figure 1 [F9]? 2. What is the highest concentration of ozone in Figure 1 [F9]? 3. What is the lowest concentration of ozone in Figure 2 [F9]? 4. What is the highest concentration of ozone in Figure 2 [F9]? 5. What is the range of Dobson values for Figure 1 [F9]? 6. What is the range of Dobson values for Figure 2 [F9]? 7. How much have Dobson values changed in this area over the last five years? Suggest reasons for the noted change. 8. What is represented by the closeness of the isodobs in certain areas of your grid? 9. In the area of this data grid ,a degree of latitude equals 111 km and a degree of longitude equals 86 km. Calculate the total number of square km represented on this grid. 10. Compare Figure 1 [F9]to a world map. What major cities and states are represented by this grid? 11. Can you make a valid statement about the ozone levels at Washington, D.C.? 12. Can you make a valid statement about the ozone levels at Antarctica? 13. What other data are needed in order to make a strong statement about ozone depletion? 14. What other studies need to be undertaken before a statement can be issued about ozone depletion? CONCLUSION Compare ozone levels in Antarctica with other global areas. What is really meant when referring to the "ozone " List all of the things you know about ozone depletion. List all of the things which you think have yet to be understood about ozone depletions. EXTENSIONS 1. Have students select varying areas to compare ozone values, i.e., rural vs. urban, marine vs. terrestrial, lowland vs. highland. 2. Have class work in groups to prepare a "strip" of Dobson value grids extending from pole to pole. 3. Have class work in groups to prepare a "strip" of Dobson value grids extending around the globe at a specified latitude. 4. Have students write the National Institute of Health for statistics on geographical occurrences of skin cancer; then have students use the ozone database to compare Dobson values of these areas with others. 5. Access the database to get the Dobson values for a specified location over the 10 years for which data has been collected. Average these values and graph the year vs. the average value. Compare this graph to the solar activity data found on the JEdI B disc. 6. Have the students design their own ozone depletion study. REFERENCE Environmental Protection Agency. 1986 Effects of Changes In Stratospheric Ozone and Global Climate, Volume 1: Overview. Sources and Resources Dr. Richard Mc Peters, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771. National Institute of Health, 9000 Rockville Pike, Bethesda, MD 20892.