Earth System Science Teachers of the Deaf Workshop, August 2004 S.O.A.R. High Using the Sun Photometer

Earth System Science Teachers of the Deaf Workshop, August 2004 S.O.A.R. High Aerosol Measurements

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High What is Aerosol Optical Thickness (AOT)? AOT is a measurement of the concentration of aerosols in the atmosphere.

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High CALIPSO will involve students by having them use a sun photometer to collect aerosol measurements from ground level for comparison with the CALIPSO satellite data. All sun photometer data collected by the students will be reported at the GLOBE website. CALIPSO students will collect AOT data from the ground.

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High How does the sun photometer measure light intensity? Photo cell converts light intensity to electric current Sun Photometer calibrated - current proportional to light intensity

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High How are sun photometers calibrated ? A “master” sun photometer is used to measure light density in Hawaii (Mauna Loa) where little or no aerosols are in the atmosphere. Mauna Loa Hawaii

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High GLOBE Sun Photometer GLOBE Video: Using the Sun Photometer

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High GLOBE Sun Photometer The GLOBE sun photometer uses a light-emitting diode (LED) as a sunlight detector. The GLOBE sun photometer has two channels: Green – detects green light, 505 nanometers A visibly hazy sky (small aerosols) is likely to have a large aerosol optical thickness at the green wavelength. Red – detects red light, 625 nanometers Red light is more sensitive to larger aerosols.

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High Where and When to do Sun Photometer Measurements same place where you do your cloud observations and other atmosphere protocols as close to solar noon as possible GLOBE Sun Photometer

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High GLOBE Sun Photometer Cooperative learning at it best: requires students to work in teams one student holds the photometer another student watches the time – 15 seconds per measurement another student watches the numbers and recalls the highest number seen during the 15 second interval another student records the time of measurements and the data students make a total of 3 red measurements, 3 green measurements, and 3 dark measurments

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High Typical ranges for AOT Note that red AOT values are typically less than green AOT values. This is due to the fact that typical aerosols scatter green light more efficiently than red light. GLOBE Sun Photometer

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High Other GLOBE measurements that are required: Record cloud cover and cloud type, sky color, and your own assessment of how clear or hazy. Sun must not be obscured by clouds. Record current temperature. Record Relative Humidity, which requires a digital hygrometer or sling psychrometer, but it is also OK to use an online or broadcast value from within an hour of your sun photometer measurements. Record air pressure using either a GLOBE-approved aneroid barometer or air pressure in (millibars of mercury) published on the Internet from the nearest local station. GLOBE Sun Photometer

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High Relative Humidity is a measure of the amount of water in the air compared with the amount of water the air can hold at the temperature it happens to be when you measure it. It is measured either with a hygrometer or sling psychrometer. Relative Humidity

CCAG Educator Workshop – Fort Collins, Colorado – July 2004 S.O.A.R. High Other things to remember: At least every three months, check the voltage of the battery in your sun photometer and replace the battery if necessary. Try to maintain the photometer at room temperature. It is very sensitive to temperature changes. GLOBE Sun Photometer