2.1 Consider This:  Ozone Levels Above Your House

What are the current ozone levels in the stratosphere? NASA can provide you with values. In fact, if a satellite is sending back data as you read this, you may be able to get today’s ozone level in the strato-sphere right above where you live.

1. NASA provides satellite data. Click on your location on the world map or enter your specific latitude and longitude to find the total column ozone amount at your location for today. Request an earlier date if today’s data are not available. As you will learn later in the chapter, 320 Dobson units is the average ozone level over the northern U.S. How does your value compare with the average?
2. Again use NASA to obtain ozone values for some other parts of the world. How do they compare with the value for your location?

2.18 Consider This:  UV Index Forecasts

The UV Index indicates the amount of UV radiation reaching the Earth’s surface at solar noon (1 p.m. daylight time).

1. The UV Index depends on the latitude, the day of the year, time of day, amount of ozone above the city, elevation, and the predicted cloud cover. How is the UV index affected by each of these?
2. The UV Index Forecast is available compliments of a satellite launched by the National Oceanographic and Atmospheric Administration (NOAA).. Account for the range of values that you see on today’s map of the U.S.
3. Surfaces such as snow, sand, and water intensify your exposure to UV radiation, because they reflect it back at you. What outdoor activities might increase your risk from exposure?

2.20 Consider This:  Bronze by Choice - Tanning Salons

The indoor tanning industry maintains a constant public relations campaign that highlights positive news about indoor tanning, promoting it as part of a healthy lifestyle. Countering these claims are the studies published in scientific journals that support the view of dermatologists that there is no such thing as a "safe tan." Investigate at least two web sites that present each point of view and list the specific claims made by each side of this issue. Based on your findings, what criteria would you use to decide whether or not a person desiring a tan should go to an indoor tanning salon?

2.21 Consider This:  Purple Octobers

NASA satellites provide stratospheric ozone data over time that can be tabulated in a number of ways, including global images, Antarctica ozone minima, and size of the ozone hole.

1. Using the web site, look first at the global imgages centered on Antarctica. Describe what is happening with the passage of time.
2. Now look at the graphs that show the minimum ozone levels and the size of the region affected. What information does each plot give you?
3. Use the information from all three views to write a description of what is meant by the term "ozone hole." In your statement, include references to the region of the globe, area affected, amount of ozone, and time.

2.23 Consider This:  Up and Down the Latitudes

In an earlier exercise, you used the Web to get stratospheric ozone data at a location of your choice (presumably above your head). Now go to NASA’s archive of satellite data on stratospheric ozone levels to find out how the values have varied between 1979 and 1992 over the lower Northern Hemisphere latitudes. You may wish to coordinate your efforts with other students, so that together you cover a range of years.

1. Obtain values of stratospheric ozone levels at latitudes from+45 degrees north to +0 (the equator) for the year of your choice. Enter -90° west (the middle of the United States) as the longitude and use the satellite Nimbus-7 and a June 15 date. Obtain readings 5° apart. Make a table of the stratospheric ozone values and compute the average.
2. Compare with others in your class data over these 13 years. Note that you may not always be able to use the average as a meaningful comparison, because satellite data may be missing at some latitudes.

2.24 Consider This:  A New Proposal - The Deep Space Connection

Two Canadian scientists proposed that high-energy radiation, sometimes called "cosmic rays", from deep space may be responsible for releasing chlorine free radicals from CFCs in the stratosphere. A publication in the August 13, 2001, issue of Physical Review Letters suggests that these cosmic rays can penetrate ice clouds, knocking electrons loose. These energetic electrons interact with CFCs to liberate the active chlorine atoms. How does this new proposal differ from our current understanding of the mechanism for production of chlorine free radicals?

2.27 Consider This:  Comparison of Northern Hemisphere Ozone Maps

Figure 2.22 shows total ozone detected in the Northern Hemisphere in March 2001. Another way to present this information is to map the total ozone percent difference between March 2001 and the March average from 1979-86. The NOAA Climate Prediction Center provides such a map. Compare these two maps and offer some possible advantages for using each type of map.