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Educational field courses for educators & students in
Costa Rica, Galápagos and beyond!
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©Holbrook Travel, Inc. 2007 IMPORTANT LEGAL NOTICE:
Holbrook Travel believes all information to be accurate at the time of
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Under Pressure
Purpose:
In this experiment, we will use the Barometer Sensor to measure
atmospheric pressure over a 24-hour period. We'll then hypothesize reasons for any changes.
Background Information:
Atmospheric pressure, measured by a barometer, is a ratio of the
force of air to the area of the surface upon which it presses down. Due to the pull of gravity, 99% of the total mass of atmospheric gases is found within 32 km of the surface of the earth, and there is less air at higher altitudes. Atmospheric pressure at mean sea level averages approximately 29.92 inches of mercury (1013 millibars Hg or 760 mm Hg), which corresponds to 14.7 pounds per square inch of air pressure.
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| Barometric pressure is an indicator of incoming weather systems.
Low-pressure systems often bring with them clouds and precipitation, because air rises in low-pressure systems. The higher the altitude, the cooler the air gets, causing condensation, clouds and precipitation. High-pressure systems usually result in mostly clear days. High-pressure systems push air closer to the ground, preventing the formation of clouds. In general if pressure rises, it's an indicator of clear weather or improving weather on the horizon. If it is falling, it can be a prelude to cloudy or possible rainy weather. If it remains steady, expect more of the same of whatever the current conditions are. |
Equipment:
Equipment Set-Up:
- Connect the USB Link to your computer's USB port.
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Connect the Relative Humidity Sensor to the USB Link.
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Data Collection Procedure:
1. If DataStudio is not already running, it will launch once the USB Link is connected to the computer.
2. Click on the "Launch DataStudio" icon in the PASPortal window.
3. We'll record data over a 24-hour period and set our sample rate, once every 5 minutes.
a. Click the Setup button (
).
b. The "Sample Period" default will read "5 Hz". Change it to "5 Minutes" by using the pull-down tab.
c. Click (
) to close the "Experimental Setup" window.
4. Click the Start button (
) to begin collecting data.
5. Click the Stop button (
) after 24 hours to stop collecting data.
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Data Analysis:
1. Scale the axes to fit the data using the Scale to Fit button (
) in the Graph toolbar.
2. Examine the graph and study the data.
3. Enter annotations noting approximate sunrise/sunset times, any change in visible weather patterns (i.e. rainstorm, clouds, wind…).
a. Click the Annotate button (
), and enter your text.
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Conclusions and Extensions:
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- Examine the graph to identify changes in barometric pressure that occurred over the 24-hour period. Did any pressure change coincide with a change in noted weather patterns?
- During what time of the year, if any, in this region would you expect to see more dramatic changes in barometric pressure during a 24-hour period? What kinds of weather patterns would these changes correspond to?
- In this rainforest environment, what would likely be the first observations you would make if the barometric pressure started falling rapidly? (Consider observations of organisms' behavior as well as atmospheric conditions!)
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| This experiment is brought to you courtesy of
PASCO. |
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Equipment
