by the Norfork School News Team
Recent graphs of Aerosol Optical Thickness
(AOT) measurements
NORFORK
ELEMENTARY SCHOOL--The new year brought some changes in science
class. Sixth grade students have begun taking measurements of
atmospheric aerosols as a part of the GLOBE Program. Aerosols are
microscopic liquid and solid particles that are floating
throughout the atmosphere that bend and scatter light that passes
through the sky. Mr. Geery (Norfork Science Teacher) made a sun
photometer from a kit designed by Ph.D. David Brooks of Drexel
University in Pennsylvania. Ph.D. Brooks is a research scientist
and the Principal Investigator for the GLOBE Aerosol protocol.
When completed, Mr.Geery sent the photometer back to be
calibrated; that means it was tested to see that accurate
measurements could be made. The sun photometer was sent back last
week and Norfork School students made their first aerosol
measurements on 14 January 2004.
The measurements that we take are of the electricity made by sunlight that is focused upon one of two different colored photocells inside the photometer. The photocells work about like the solar panels on a student math calculator, except that they "see" only one wavelength of light out of the whole visible spectrum. One is red and the other is green. Each senses how intense the light is and sends a small signal to an amplifier microchip which boosts the signal to a level that can be measured by a digital voltmeter. These voltages as well as a very accurate time measurements made using a hand-held Global Positioning Satellite (GPS) receiver are entered into the GLOBE database via the internet. The results are sent back to us as a number which represents the Atmospheric Optical Thickness, or AOT, which tells us how much haze or distortion happens to sunlight that day. With these facts we know what is normal and we will try to look for the causes of any abnormal measurements.
Measurements cannot be made every day. The weather must be clear with no clouds between us and the sun. Even the slightest clouds or contrails will distort these precise measurements and ruin the data. So students have to be very careful in looking for the high cirrus clouds that are almost transparent or very pale colored. So far, our measurements have been valuable to us as well as research scientists who also use our data in their investigations. Smoke from burning leaves and grassland fires in the area caused higher than normal AOT values on our earliest measurements. Further data collection will let us know how abnormal the smoke made our atmosphere that day and how many more days are like that.
Congratulations to all the students involved in making these measurements. Your data is very important to us all.
Published in our school newspaper "Panther Press", January 2004.