Preface: What is my latitude and longitude?
DIRECTIONS: Read each instruction carefully

-Before we begin this activity, it is important to know the latitude and longitude of where you
live. If you know your latitude and longitude in degrees, write it in the boxes below. If you
don’t know it, use an atlas.

Latitude: Longitude:


If you don’t know your latitude / longitude, or to be more precise, try...
Step 1- Go to http://www.mit.edu:8001/geo
Step 2- Enter the name of your town
Step 3- Enter your latitude and longitude in degrees above.

Section 1: How much ozone is above my head?
DIRECTIONS: Read each instruction carefully

-Between your head and outer space is a layer of gas called ozone. As you have already learned, ozone
protects you from harmful sun rays.

1. If you were able to take a giant net and collect all the ozone that is DIRECTLY above your head, how
thick would the layer of gas be?
Take a guess... Make sure your answer is metric! ___________________

2. Convert your answer to #1 in mm, and multiply by 100 _________________

-You just converted your answer to DOBSON UNITS (DU)!
-A Dobson Unit is defined as a .01mm layer of ozone at 0C and 1atm pressure. (Simply put, it is how big the ozone layer would be at the surface and 32°F).

To better explain Dobson Unit, consider this graph:

3. Practice converting between DU and mm of ozone at 1atm / 0 degrees C:
(a) If I had 20mm-worth of ozone above my head, what is that in DU? ______DU
(b) How thick in km would 5000 DU of ozone be? __________________km

4. FIND OUT HOW MUCH OZONE WAS ABOVE YOUR HEAD YESTERDAY:
Step 1- Go to http://jwocky.gsfc.nasa.gov/ozone_overhead.html
Step 2- Enter YESTERDAY’S date
Step 3- Enter the latitude and longitude. (NOTE: You must enter
NEGATIVE numbers for SOUTHERN latitudes and
WESTERN longitudes)
Step 4- Press “Submit” and write the answer below.
_______________________ DU

5. With a ruler below, draw the thickness of the ozone over your head yesterday.

6a. How close were you to your original guess in question #1? ____________ DU
b. Why do you think they were different, and are you surprised?

SECTION 2: How does ozone change above your head?
DIRECTIONS: Read each instruction carefully.

-Ozone amounts are not stable, they change!

7a. Guess how long it takes ozone amounts to change about 5DU.
_____________________________________________________________
b. Guess the range of DU in one year above your head. (Simply guess what the lowest amount would be,
and subtract that from the highest amount).
___________ DU

8. Let’s find out exactly how ozone changes above your head. Use the website given in question 4 to
complete the table below. (The ozone amount for yesterday is simply your answer for question 5.)

DATE Ozone amount (DU) Change from yesterday
Yesterday ( / / )
2 days ago ( / / )
3 days ago ( / / )
Last week ( / / )
Last month ( / / )
2 mths ago ( / / )
3 mths ago ( / / )
6 mths ago ( / / )
9 mths ago ( / / )
1 year ago ( / / )

9a. Does ozone change more or less frequently than you thought in question 7?
b. Is the ozone change more or less severe than your guess in question 7?

10a. Although we have a rough idea of how ozone changes above your head, why is the chart above
probably not the best way of finding the highest and lowest ozone values within the past year?
b. What would a scientist have to do to figure out the real range of ozone values within the last year?

SECTION 3: How do we get ozone data?
DIRECTIONS: Read each instruction carefully.

Step 1- Go to http://jwocky.gsfc.nasa.gov/sat.html
Step 2- Read about the satellites (and look at their pictures) to
answer the questions

11. What satellites gave us these pictures of the ozone layer, AND what years did they supply data?
Fill in the chart below.

12. Which satellite gave you the ozone information from yesterday?
13. How high is this satellite’s orbit today? __________________
14. How long does it take this satellite to orbit the Earth? ____________
15. What was unique about how the most recent satellite from July 1996 was launched?

SECTION 4- Ozone changes all over the world--The ozone hole
DIRECTIONS: Read each instruction carefully

-Every part of the globe has different amounts of ozone above it.
-By the mid 1980’s, ozone amounts over Antarctica were so low, that
scientists called it the “ozone hole”.

Step 1- Go to http://jwocky.gsfc.nasa.gov/eptoms/ep.html
Step 2- Find the most recent ozone hole animation (Antarctica).
Step 3- Watch the animation (replay it if you need to) and
answer these questions.

NOTE: The black spaces are missing data, not a lack of ozone!!

16. What dates does the ozone hole seem its biggest and worse? _____________
17a. What appears to be the lowest ozone value given (roughly)? __________DU
b. How thick would this layer be at surface pressure? ________mm
c. Use a ruler to draw that thickness in the space below...

18. Where is the lowest value on the last date of the animation?_______________

Step 1- Note the last date, and approximate the latitude and
longitude in degrees of the area you found in question 18.
(HINT: If you need help with the latitude and longitude values, you
can “cheat” by using http://jwocky.gsfc.nasa.gov/latlon.html )
Step 2- Go to http://jwocky.gsfc.nasa.gov/ozone_overhead.html
Step 3- Enter the latitude, longitude and date to find out the
EXACT lowest ozone value.

19. What is the exact ozone value? ______________DU

Step 1- Go back to http://jwocky.gsfc.nasa.gov/eptoms/ep.html
Step 2- Find the most recent Northern Hemisphere low ozone
animation and play it.

20a. Is the low ozone over the North Pole worse than the South Pole? ____
b. Is the low ozone over either pole MORE than the low ozone over your head?
c. How do you know for sure?