Costa Rica Rainforest Experiment
"Under Pressure"

- Equipment
- Data Collection Procedure
- Data Analysis
- Data Table
- Conclusions and Extensions

PASPORT Barometer Sensor
(PS-2113)


Purpose

To measure the change in atmospheric pressure over 24 hours.

Overview

In this activity, students will use a PASPORT Barometer Sensor to measure the change in atmospheric pressure over a 24-hour period of time. Students will then discuss how the changes they observe are indicative of the weather over that time period.

Background Information

Atmospheric pressure 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 kilometers 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 milibars or 760 mm Hg), which correspond s to 14.7 pounds per square inch of air pressure.

Barometric pressure is an indicator of incoming weather systems.  Low-pressure systems often bring with them clouds and precipitation because air rises in a low-pressure system.  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, rising pressure is an indicator of clear weather or improving weather conditions.  If pressure is falling, cloudy or rainy weather is likely.

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Equipment

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Data Collection Procedure

GLX Setup:

  1. Plug the PASPORT Barometer Sensor into the port on the top of the Xplorer GLX.

  2. From Home screen, press I to access the Sensors screen.

  3. Press c to change the sample rate unit to minutes.  Change the sample rate to 5.  The Barometer Sensor is now configured to take data every 5 minutes.



Equipment Setup and Recording Data:

  1. Place the GLX and Barometer outside in a dry place

  2. Press s to begin recording data.

  3. Allow the GLX to collect data for 24 hours.  Keep note of the changes in weather conditions.

  4. Press s to stop collecting data.

Analysis

1. From the Home screen, press F to open the Graph display.

2. Examine the data. Note approximate sunrise and sunset times and any changes in visible weather patterns.

Data

Start Time  
End Time  
Recorded Sunrise  
Recorded Sunset  

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Conclusions and Extensions

1. Did any pressure changes coincide with a change in weather patterns?

2. During what time of the year, if any, would you expect this reason to see more dramatic changes in barometric pressure during a 24-hour period?  What kinds of weather patterns would these changes correspond to?

3. In this rainforest environment, what would likely be the first observations you would make if the barometric pressure started falling rapidly?

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Back to Costa Rica Summary -- October 2002