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The Research Experience for Teachers Program
Introduction/Motivation:
What is the Ozone Hole?
Source: NASA Ozone Hole Watch and Science Education Resource Center at Carleton College
The "ozone hole" is an area where the amount of ozone is depleting in the stratosphere.
Generally, the hole begins to appear during the spring (August – October) in Anartica. The
effects of the ozone hole aren't limited to Antarctica. On the graph they appear has dark blue
and purple color.
Risks for Humans
“The most immediate danger the ozone hole poses for humans is that with less ozone in the
atmosphere, more ultraviolet (UV) energy or UV rays reaches Earth's surface.” UV rays can
damage the eyes, causing cataracts, and can cause skin cancer of humans. It is important to
put on sunscreen when you are out in the sun for a long period of time to protect your skin.
You should also wear sunglasses to protect your eyes from the UV rays. Do you know of any
other dangers of the UV rays?
Materials List:
•
ImageJ software
•
Excel Software
•
Southpole and Northpole ozone images (Associated files)
Procedure:
Background:
Through looking at images of the Ozone hole over the South Pole (Antarctic region), you will
learn how the Ozone hole changes year to year. You will analyze images of the hole during its
maximum month, October, to see if and how it has changed over the past ten years. Using
ImageJ, you'll highlight and measure the area of the hole each year, then export your results to a
spreadsheet application and produce a graph of your measurements.
The images show the amount of ozone overhead, measured in Dubson Units (DU). The ozone
hole is defined as the area where the total amount of ozone is less than 220 DU. The color scale
in the images has a limit at 225 DU, so you will use that value as the threshold value for the
ozone hole.
Preparation:
You need to make sure that ImageJ and Excel or similar spreadsheet software are
available on your computer. You will also need the images that are included in the
associated files.
Lab Activity:
1. Save the image files (.TIF), these are images from 1996-2005, in a Folder that you will name
as South pole ozone.
2. Open Imagej
3. In Image J Click File>Import>Image Sequence>South pole ozone folder>Click on the
first image>Okay to default settings. This will stack your images in order. You can flip
through using the slider at the bottom or use the > , < key.
4. Remove the continent outlines select Process > Noise > Despeckle, Yes
5. Can you identify the ozone hole in the images? Do not make any changes yet!
6. Select Image > Adjust > Threshold this will specify the range of pixels.
7. Check the box for Dark Background. Drag the bottom slider so that pixels representing ozone
measurement of 225 and lower are RED and pixels of higher ozone levels remain unchanged
close the window. You should see on the bottom scale that from 100 to 225 should be
covered in red that will correspond to your image. Close window. (If when you click dark
background and the background becomes completing red, uncheck the dark background, the
background around the picture should be white like the screenshot below).
8. On the ImageJ toolbar click the wand (tracing) tool and click it just left on the group of red
pixels on the image that represent the ozone hole. You should see a yellow line around the
red pixels representing the ozone layer.
9. Click Analyze > Measure you will see your results in the results window.
10. Complete steps 8 and 9 for the remainder of the images. To move to the next image either
use the slider at the bottom or use the >, < key.
11. Save the Results by choosing the Results window. File > Save As keep as Results.xls.
Data Analysis Procedure:
1. Open Excel
2. Open the File Results.xls Go through the text import wizard, do not change anything
until step 3 of the wizard. You will set the first column as text.
3. Change the first column header to Year.
a. Change 1-10 in the first column to the years (1996 to 2005).
4. Highlight the first 2 columns, insert Area Chart.
5. Save your results.
Graphical Analysis:
1. Did the size of the ozone hole increase, decrease, or stay the same over the 9 years?
What might account for the changes?
2. Compare the South Pole ozone hole to the Northpole ozone hole. Save your results of the
south pole ozone and send it to your teacher. What differences did you notice between the
South and North Poles ozone hole?
3. Using the South Pole pictures compare the images of August 1, 1996, September 1, 1996,
October 1, 1996. Save your results and submit to your teachers. What was the difference
between August to October ozone holes?
4. What are the dangers of UV rays other than the examples mentioned?
Reference(s):
NASA Ozone Hole Watch
National Geographic Whatever Happened to the Ozone Hole?:
http://news.nationalgeographic.com/news/2010/05/100505-science-environment-ozone-hole-25years/
Ozone Images
https://ozoneaq.gsfc.nasa.gov/data/ozone/