How Does the Ozone Layer Change over Time?
ES1708  Annual Global Ozone Variation

The TOMS (Total Ozone Mapping Spectrometer) instrument creates daily images of global ozone. These images can be animated to show changes in the ozone layer over time.

  !   Click the top image to see an animation of monthly ozone images. Step through the animation to observe the chages in ozone levels over both poles through the year.

Ozone is measured by reflected sunlight. The gray bars across the top and bottom of the animations represent areas where data were not collected because the sun was not shining.

NASA
Monthly global ozone levels for 1999.

  !   Click the bottom image to open a second copy of the same movie.

This will allow you to set up monthly comparisons. For example, you may want to compare the January image with the June image by looking at them both on the screen at the same time. Use the animations to answer these questions.

1. During which months does the South Pole have the lowest concentrations of ozone? Estimate the minimum ozone level.

2. During which months does the South Pole have the highest concentrations of ozone? Estimate the maximum ozone level.

3. During which months does the North Pole have the lowest concentrations of ozone? Estimate the minimum ozone level.

4. During which months does the North Pole have the highest concentrations of ozone? Estimate the maximum ozone level.

5. Describe how ozone concentration changes over the North and South Poles through a year. Compare minimum ozone levels for each pole.


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