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Activity: Build a Weather Station

Equipment Needed for this Project

• Thermometer: (To measure the temperature of the air). For this activity it is easiest to purchase a simple indoor-outdoor Celsius thermometer.
• Anemometer: (A wind gauge to measure the direction and speed of the wind). Details for the construction of a simple anemometer and wind direction sensor follow.
• Barometer: Is also needed and can be easily constructed as part of this project. Calibration of the barometer is not essential to the success of this project.
• Notebook: In which to record observations.

Thermometers

The simplest (and best) approach to making temperature measurements is to purchase an inexpensive indoor/outdoor Celsius thermometer. Very inexpensive and reasonably accurate, thermometers can be purchased at discount stores.

Figure 6: Simple inexpensive indoor-outdoor thermometer.

Weather Vanes and Anemometers

You can easily build a weather vane using thin plywood or heavy cardboard. Use a magnetic compass to align the North-South direction and mark these directions so that they can be easily identified. NOTE: The direction of the wind is defined as the direction from which the wind is coming. For example, when you face into the wind, the direction you are looking is the direction of the wind.

Determining the wind speed is slightly more difficult. Installing a tether (or telltail) on the tail of the vane will allow you to determine the relative wind speeds. The higher the angle of the telltail, the higher the wind speed.

Figure 7: A wind direction vane is relatively easy to build. A sturdy piece of cardboard pivoted on a heavy stand will give the wind direction. Give your vane a couple of coats of waterproof latex paint before placing it outside.

Barometers

The earliest reliable barometers consisted of a long thin tube (about one metre in length) sealed at one end. The tube was first completely filled with liquid mercury. The open end of the tube was inverted in a dish of liquid mercury so that air could not enter the tube. The downward weight of the mercury column caused it to fall so that a vacuum formed in the upper sealed end of the tube. But why didn't the entire column of mercury pour out of the open end into the dish?

The answer is that the pressure of the atmosphere pushing against the vacuum in the tube held the column of mercury up in the tube.

Figure 8: A schematic diagram of a typical mercury barometer. The height of the mercury column indicates the air atmospheric pressure (often expressed in inches or millimeters).

Building a Barometer

It is quite easy to build a simple barometer that can be used to study the Earth's changing atmosphere. There is a strong correlation between atmospheric pressure and weather. In this activity you can discover this correlation.

The meteorological instruments aboard the Phoenix Lander will seek to identify similar correlations in the weather patterns of Mars.

Materials

1. An empty and dry 2L juice can with the lid completely removed
2. A toy balloon either vinyl or latex
3. A few sturdy elastic bands
4. Tape
5. Soda straws (2 or more)
6. A few pieces of construction paper

Figure 9: The basic materials needed to build a barometer.

Construction Overview

Figure 10: The basic design of the barometer. This barometer is very temperature sensitive, therefore it is very important that you place it in a location which will remain at a constant temperature.

Figure 11: Photos showing the details of the barometer construction. Notice that a thermometer has been placed beside the barometer to ensure that the temperature at each reading is always the same.

Figure 12: As the external air pressure changes it will cause the balloon to bend inwards or outwards at the centre. The effect will be to cause the far end of the soda straw to move up or down according to the pressure. Pressure readings should be taken at least 5 or 6 times each day.

Activity

Set up your weather station and set up a journal in which to record your observation. You will need to keep records for at least several weeks in order to discover any local weather patterns in your data that apply to your geographical location.

Make neat, well scaled, graphs of your data. HINT: If you use the same time scale on the x-axis for all your graphs, you can line your graphs up, one below the other to identify trends and patterns.

Keep a journal

The key idea is to look for patterns so that accurate weather predictions can be made based on the patterns that have been discovered. Impressively accurate 12 hour forecasts can be made based on barometric observations alone. Hint: to make weather predictions based on the barometer readings, look at the rate and direction (i.e. is the pressure increasing or decreasing) of the pressure changes rather than the barometric pressure itself.

Figure 13: The essential element in doing good scientific research is accurate and detailed record keeping. Graphs are the best way to expose trends and patterns.

Extension Activities

1. Design a method to calibrate the telltale on the wind vane in kilometres per hour.
2. Design a method to calibrate your barometer in kilopascals.
3. Make a series of 12 hour weather forecasts based on your barometric readings and compare your predictions with those of you local newspaper or radio/TV station. Use the Traditional Barometric Weather Chart included in the Resources section.