Be Your Own Weather Person
Make a Barometer: Observing Air Pressure Changes
Air pressure is quite complicated, but the best way to describe it is the weight of the air. So pressure is the amount of weight the atmosphere presses down on the Earth’s surface. At the top of mountains the pressure will be lower than at sea level. When air is heated along the surface of Earth, it becomes less dense and rises up into the sky. Since it it rising up from the Earth the pressure of the air decreases. When air aloft cools it becomes more dense and sinks. Since the air is moving downward it generates higher pressure on the ground. Wind occurs when air moves from areas of higher air pressure to lower air pressure. When air moves upward (low pressure) it cools, and the water in it condenses to form clouds. If there is enough condensation the clouds could produce rain or snow. Falling air (higher pressure) usually results in clear skies and good weather. If you could measure the air pressure you could predict the weather.
Air pressure can be measured using a cool gadget called a Barometer.
- Jar or sturdy plastic cup
- Rubber Band (to fit around jar opening)
- Paper or cardstock
- Pen or pencil
*Make sure you have a grown-up’s help for this project.*
- Cut the balloon at the base of the neck.
2. Stretch the balloon over the opening of the jar, and make it as flat as possible across the center. Hold it in place with the rubber band.
3. If the straw has a bendy part, cut that part off. Tape the needle to the straw, toward the end so that part of the needle extends past the straw. Tape the opposite part of the straw across the center of the balloon.
4. On the paper mark “High” and “Low” on the side where the needle is pointing. Place the paper behind the jar or cup (you may need to tape the paper to the jar to hold it in place) and mark where the needle is pointing. Check back every few hours and note where the needle is pointing.
5. Keep a separate chart of dates, highs and lows, and temperatures. Do you notice any patterns? How can this help you predict the weather?