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Measure the aerosol optical thickness of the atmosphere (how much of the sun’s light is scattered or absorbed by particles suspended in the air). Students point a GLOBE sun photometer at the sun and record the largest voltage reading they obtain on a digital voltmeter connected to the photometer. Students observe sky conditions near the sun, perform the Cloud, Barometric Pressure and Relative Humidity Protocols, and measure current air temperature.

Protocols to help in completion of the main protocol.

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Students use an aneroid barometer to measure barometric pressure in support of the Aerosols and Water Vapor Protocols.
Observe and report which types of clouds are visible, how much of the sky is covered by clouds, and the opacity of clouds. Also report sky and surface conditions. Each observation is matched to satellite data of clouds taken about the same time and location. Cloud observations can be taken at any time! This Protocol is designed to be flexible and fit into your schedule, classifying, observing, and reporting cloud observations when it works for you. If you observe while a satellite is overhead, you can then receive an email from NASA comparing your observations to satellite data.

NASA Support Page for GLOBE Clouds and Satellite Comparison
Your cloud observations help NASA to better understand the different types of clouds and the effects they have on our Earth’s climate. NASA matches cloud observations to corresponding satellite data. Satellites only see the top of the clouds while you see the bottom. By putting these two vantage points together we get a much more complete picture of clouds in the atmosphere.

Find Satellite Overpass Times by accessing the NASA Cloud Satellite Portal.
Measure the current air temperature when an instrument shelter is not available. Current air temperature is measured using a thermometer held in the open air but in the shade for at least 3 minutes.
Students measure the relative humidity using either a digital hygrometer or a sling psychrometer.
Students use an infrared thermometer (IRT) to measure the temperature of Earth's surface.

Step-by-step instructions for collection data according to the protocols.

Sheets to be filled out during data collection.

Activities to help students learn more about the instruments and protocols.

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Students are introduced to the concepts of solar elevation angle and relative air mass and learn how to determine relative air mass from measurements of solar elevation angle.
Students draw a visualization and learn about all the design choices involved and how these choices affect what is communicated by the visualization.
Students use visualizations to explore the relation between elevation and temperature and begin learning how to make important patterns evident in visualizations.
Students study the movement of the sun during the day by making quantitative observations of the direction and length of the shadow cast by a stick (known as a solar gnomon).
Students observe sky color and learn to associate color with the presence or absence of aerosols.

Additional documents or tools related to the protocol.