"The Missing Link"

WEB SHEET

Before you begin-Make sure you have:

(1) A Pencil

(2) A blank WEB ANSWER SHEET

PREFACE- Calibration

SECTION 1- How do you measure ozone from the ground?

SECTION 2- How do satellites measure ozone data?

SECTION 3- How do we know the satellite is correct?

SECTION 4- The case of the missing data

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Preface: Calibration

DIRECTIONS: Read every instruction carefully. Put your answers to questions on the answer sheet.

When your teacher tells you to, on your answer sheet, write down the Room clock time, Your time, and then answer the questions on your answer sheet.

-What you will do, is calibrate your time to the room time.
-Scientists must do this frequently in order to make sure data is correct!!!

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SECTION 1: How do you measure ozone from the ground?

DIRECTIONS: Read every instruction carefully. Put your answers to questions on the answer sheet.

-Between your head and outer space is a layer of gas called ozone. As you have already learned, ozone protects you from harmful UV sun rays.
-Ozone is measured in Dobson Units.
-1 Dobson Unit = 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).
For a more thorough explanation, go to http://jwocky.gsfc.nasa.gov/dobson.html
-Scientists on the Earth can use ground instrument to measure ozone from the surface. Actually, it really measures the amount of UV being absorbed by the atmosphere. Then, it calculates how much ozone must be present to absorb it (in DU).
-Measurements are usually taken near noon local time.
-There are roughly 350 of these stations located around the world.

Photo courtesy of L.J.B. McArthur at http://www.tor.ec.gc.ca/woudc/bdms/

Brewer Ozone Measuring Instrument

LET'S GET ONE PIECE OF DATA...

EXAMPLE: What was the ozone reading for Wallops Island, VA on Jan. 30, 1987?

Step 1- Click on---> http://www.tor.ec.gc.ca/woudc/stations/stations.htm ...now we have a clickable map.
Step 2- Click on North America
Step 3- Choose the United States of America
Step 4- Scroll down to "Wallops Island"

Now, we know the station number is #107

Step 5- Close the NEW window by clicking on the box in the upper left. DON'T CLOSE THIS WINDOW!!!

Step 6- Click on---> ftp://woudc:woudc*@ftp.tor.ec.gc.ca/wodc/archive/tot/stn107.tot

Step 7- Scroll down until you see 87/01/30 (this is Jan 30, 1987)

Now, we know that the ozone amount was 331 DU.

1. What is the ozone reading for Wallops Is, Va (st. 107) on Jan 30, 1989?

2. What is the ozone reading for Huancayo, Peru (st. 110) on 2/22/64?

3a. What station number is BelgranoII, Antarctica (Italy-Argentina)? Use the information above to help you.
b. What was the ozone reading there on 10/1/92?
c. What was the ozone reading there on 12/12/92?
d. How much did the ozone change over that 70 day time span?
e. What do you think caused the reading on 10/1/92?

CLOSE the new window!!!

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SECTION 2: How do satellites measure ozone data?

DIRECTIONS: Read each instruction carefully. Put answers to questions on your answer sheet.

- A satellite is just like a ground instrument, however, they are viewing the measurements from above in space.

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

4. When did these satellites supply data? Fill in the remainder of the chart on your answer sheet..

Step 3- CLOSE the NEW window!

- NIMBUS-7, METEOR-3, and ADEOS TOMS have given us ozone information above different cities as well.

EXAMPLE: What was the ozone reading above Arosa, Switzerland on 1/1/80?

SINCE IT WAS 1980, WE NEED TO USE NIMBUS 7 (other's weren't launched yet!)

Step 1- Go to TOMS homepage (http://jwocky.gsfc.nasa.gov/main.html)
Step 2- Click on "Ozone Archive" at the top.
Step 3- Click on "NIMBUS-7"
Step 4- Click on "Overpass Data for 371 ground sites
Step 5- Click on "Arosa, Switzerland"
**If you wanted another city, you would simply select it**

NOTE: Dates are written in the left-most column as year, followed by the day# of the year. For example, "80001" is Day 1 of 1980 (Jan 1). "86059" is Day 59 of 1986 (Feb. 28).

The columns are written:
YRDAY ?? ????? LAT LON OZONE

Now, we know the answer is 343 DU

5. What is the ozone amount over Arosa, Switzerland on Jan 10, 1979?
6. What is the ozone amount over Athens, Greece on Feb 1, 1979?
7. What is the highest ozone amount recorded in Athens, Greece in 1980?

Close the NEW window.

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SECTION 3: How do we know the satellite is correct?

DIRECTIONS: Read each instruction carefully. Fill in the answers to questions on the answer sheet.

-Above, we have accessed satellite data, and ground data.
-All ground stations are calibrated to Station 83 (Boulder, Colorado). Every Summer from May-August, this station is taken to a high-altitude observatory in Mauna Loa, Hawaii to be recalibrated.

Courtesy: http://mloserv.mlo.hawaii.gov/

-TOMS instruments on satellites are calibrated by comparing them to the ground instruments. Let's look at a general example.

Click HERE and answer the questions below.

8. The blue line is the data taken from Arosa. The green line is TOMS data.
a. How does TOMS compare to Arosa? ( higher lower exact )
b. What are the similarities the two instruments have?

9. Think of one reason why they may not EXACTLY match.

Close the NEW window.

-Usually, as long as one instrument is consistently higher, lower, or close to the other, we consider the instruments calibrated.
-In general, in order to calibrate it properly, we need to AVERAGE the data over a period of time. This helps scientists come up with how the ozone (or other data) is changing over long periods of time.
-It is also important to look at the TRENDS and make sure that they match. When ground instruments show a decline in ozone, the satellite should measure a decline as well.

10. Let's look in a little more detail. Using the ground data, and the NIMBUS satellite for Cairo, Egypt, complete the chart on your answer sheet and answer the questions: You will need to go to ftp://woudc:woudc*@ftp.tor.ec.gc.ca/wodc/archive/tot
11. What are two correlations you noticed between NIMBUS 7 and the ground?
12a. What was the average ozone value from NIMBUS-7 over 10 days?
b. What was the average ozone value from the ground over 10 days?
c. What was the difference between the averages?
d. What is the percent difference? Round to the nearest whole number.
Percent difference = (Av. Ground-Av. NIMBUS)
Av. Ground

KEEP THE WINDOW OPEN!!!

- Basically, we have a general idea how the satellite is calibrated to the ground station, and visa versa. If the percent error were to change dramatically in the next few years, you would know something was wrong.

13. This time, let's look at data from Cairo, Egypt in 1993 to see if any major changes have occurred. Fill in the chart on your answer sheet.
14a. What was the average ozone value from NIMBUS-7 over 10 days?
b. What was the average ozone value from the ground over 10 days?
c. What was the difference between the averages?
d. What is the percent difference? Round to the nearest whole number.
15. Was there any change in percent difference over the last 2 years?
16. What two dates in the table above would you suspect faulty data from either the ground or satellite and why?
17. How could you be sure that the satellite was not faulty?

CLOSE the NEW window!

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SECTION 4- The case of the missing data.

DIRECTIONS: Read each instruction carefully

-Missing data points occur frequently in science.
-When you are faced with a missing point, you pretty much have to make an estimate as to what the missing point would be by looking at the points before and after.
-Scientists use as much information as possible before making a their estimate. Then, they use that information to validate their estimate.

You will need TWO windows open for this section. Try to "split" the screen in half. Click on the TOMS website and put it in the lower half (manually shrink or enlarge the window by clicking and dragging the lower right corner), then, click on the ground data website and resize it so it fits in the upper half of the screen. Then, answer these questions. (If you ever accidently close a window, simply click on the links again below.

TOMS WEBSITE

GROUND DATA

18. There is a missing data point in the NIMBUS-7 overpass data for Cairo, Egypt on Aug. 12, 1982 (day #224).
a. Go to the TOMS website and estimate what the missing point would be.
b. Go to ground data to find out what the actual ground measurement WAS.
c. What is the difference between the your estimate and the ground measurement?
d. What is the percentage difference?
e. Does the your estimate and the ground data have the same trend? (In other words, do they both decrease or increase?)
f. Explain if your guess is a good estimate.

19. A harder question. NIMBUS-7 stopped collecting data on May 6, 1993 (day 127). Look at Cairo, Egypt and answer these questions:
a. Explain if the last data point taken by NIMBUS-7 over Cairo (286DU) is a reliable measurement.

b. Can you estimate what NIMBUS-7 might have recorded on day 127 (May 6, 1993) had it still been operational?

20. The hardest question. METEOR-3 did not take data for an extended period in Dec-Jan 1992. What might METEOR-3 have measured over Melbourne, Australia on Jan. 1, 1992? Be sure to VALIDATE your guess before you are finished!
HINT: This might require the tables on your answer sheet.

21. Give two reasons why data verification is important.