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Weather Projects for Young Scientists
Experiments and Science Fair Ideas
By Mary Kay Carson
Chicago Review Press Incorporated Copyright © 2007 Mary Kay Carson
All rights reserved.
The Air Around Us
The earth is surrounded by a blanket of air called the atmosphere. Earth's air is mostly nitrogen and oxygen gas with small amounts of water vapor, carbon dioxide, and a few other trace gases. (See the pie chart at right.) The earth's gravitational pull anchors the atmosphere to the planet. Gravity keeps air from drifting off into outer space.
Layers of Air
Scientists divide the atmosphere into four main layers. (See diagram on page 3). The layer closest to the ground is the troposphere. It goes from the surface to about 7 miles (11 km) up. It has the most air and moisture of all the layers. It's where most weather happens. In this layer temperature decreases with height, so higher altitudes are colder. The stratosphere is from about 7 to 30 miles (11 to 48 km) above the ground. There is little mixing between the stratosphere and the troposphere, so hardly any water vapor and dust make it into the stratosphere. At the top of the stratosphere — and into the mesosphere — is the ozone layer, the band of O3, or ozone, that blocks much of the sun's dangerous ultraviolet (UV) radiation from reaching the earth's surface. Ozone blocks UV radiation by absorbing it. While doing so, it also heats up the stratosphere, which is actually warmer at its top than at its bottom.
The mesosphere is from 30 to 50 miles (48 to 80 km) above the earth. The temperatures in this layer again begin to decrease with height, reaching as low as -90°F (-68°C). No commercial aircraft fly this high, only research weather balloons. The thermosphere is the layer from 50 to 180 miles (80 to 290 km) up, or more. After it is interplanetary space, or the exosphere. It gets super hot in the thermosphere, up to more than 3,000°F (1,650°C). The lower part of the thermosphere is also called the ionosphere and contains electrically charged particles or ions. Radio waves are reflected back to the earth by this layer. It's also where high-energy atomic particles from the sun collide with gases and produce beautiful streaks of colored light called auroras, or the northern lights.
You can make a great poster for your room of the layers of the atmosphere. Start by covering a section of a wall with paper or poster board. Use the information in The Atmosphere's Layers diagram on page 3 to help you draw the layers in correct proportions. If you have about 10 feet (3 meters) of wall height, use the scale of 1 cm = 1 km.
Once the layers are drawn and labeled, find out the characteristics of each atmospheric layer. Then write up an informational caption for each layer and paste it onto the poster inside the correct layer. Include the atmospheric layer's temperature, gases, atmospheric phenomena, and what human-made aircraft travel in that layer. You can also illustrate the layer with jets, space shuttles, meteorites, satellites, etc.
The Weight of Air
Air is invisible and may seem like it's made up of nothing at all. But the gases in air have weight and take up space. The weight of the air pushes on the earth's surface, just like a stack of blankets pushes down on a table. This pushing force is called air pressure. At sea level, air pressure is about 14.7 pounds per square inch (1 kg/cm2). Air pressure lessens with height, however, halving about every 3.4 miles (5.5 km). There's less air pressure on top of a mountain than at sea level. We're literally living at the bottom of an ocean of air!
Air Is Everywhere
Air may be made up of invisible gases, but it takes up space. Prove to yourself that air has volume in this activity.
* funnel with a very narrow tip
* small clear plastic bottle (such as a salad dressing bottle)
* sharpened pencil
* modeling clay
1. Set the funnel inside the neck of the bottle. Think about what's filling up the inside of the "empty" bottle.
2. Pour water through the funnel until the bottle is halfway filled. Is there still air in the bottle? What happened to it?
3. Empty the water out of the bottle and replace the funnel.
4. Wrap a "collar" of modeling clay around the mouth of the bottle, so that it seals in the funnel. It needs to be airtight!
5. Try again to pour water through the funnel into the bottle. What happens? What's blocking the water from flowing in?
6. Now use the sharpened pencil to poke holes in the clay collar. What happens? How did the air that was trapped in the bottle escape?
Air may feel like nothing, but those gases do weigh something. Prove to yourself that air has mass in this activity. (Remember, weight is mass times gravity.)
* 2 identical balloons
* 4 four-inch (10-cm) strips of tape
* 2- to 3-foot-long (0.5–1 m) thin dowel or yardstick
* straight pin
* friend to help
1. Blow up the balloons to equal sizes and tightly tie them closed.
2. Tape the balloons onto the ends of the dowel or yardstick using two equal-sized strips of tape on each balloon.
3. Tie the string loosely around the dowel or yardstick near its center. Hold the string away from your body and ask your friend to slide the string loop back and forth until the balloons balance.
4. Continue to hold the balancing balloons by the string.
Have your friend CAREFULLY puncture one of the balloons with the straight pin by sticking it through a taped area. (This will keep the balloon from popping, the air will seep slowly out instead.)
5. What happened? Why are the balloons no longer balanced? What does the deflated balloon no longer have?
Pressure vs. Pencil
Anything that has weight and takes up space — like air — also exerts pressure. Living under the miles of atmosphere above us is like being under an ocean of air. Prove to yourself how air exerts pressure in this activity.
* unsharpened pencil
* 3 identical sheets of paper
1. Fold one sheet of paper in half and one into quarters. The third is left as is. Which of these papers weighs more?
2. Lay the pencil on the end of a desk or table so about 2 inches (5 cm) of it hangs over the edge. Set the quartered sheet of paper on top of the part of the pencil on the desk.
3. Tap the pencil with a quick, but gentle, downward stroke. What happens? Did you feel a lot of pressure pushing against the paper? Was it hard to flip the folded paper?
4. Repeat steps 2 and 3 with the halved paper. (Make sure you are tapping with the same strength.) What happens? Why did it feel harder to flip?
5. Repeat steps 2 and 3 with the open sheet of paper, again using equal force when tapping the pencil. What happens? What is keeping the paper "glued" to the desk? Why is there more air pressure pushing down on the unfolded sheet of paper
Highs and Lows
You already know there's more air pressure at sea level than on top of a mountain. But air pressure changes not only with height, but also with temperature. Warm air weighs less than cool air, so it rises. Warm air rises because its fast-moving molecules spread out, making warm air less dense and lighter than cool air.
An area of air that has a higher pressure than its surroundings is called a high pressure system or, or simply a high. The sinking air of a high pressure center dampens the upward movement of air needed for clouds to form. This is why an area of high pressure often brings clear weather. In contrast, a low pressure system (or low) has rising air, which encourages clouds to form and the rain or snow that comes from those clouds. Cloudy and rainy weather often result from an area of low pressure. The formation and movement of high and low pressure areas in the atmosphere drive much of the weather around the globe.
Air pressure is measured with an instrument called a barometer. (That's why air pressure is also called barometric pressure.) There are two basic kinds of barometers — the mercury barometer and the aneroid barometer. The mercury barometer was invented by an assistant of Galileo Galilee named Evangelista Torricelli in 1643. It's a simple instrument that has changed little since its invention. A mercury-filled tube that's closed at one end is placed upright with its open end down into a container of more mercury. Air pressure on the mercury in the container keeps the mercury from draining out of the tube. The more air pressure there is, the greater the pressure on the mercury in the container, and the higher the mercury in the tube is pushed up. A ruler set beside the tube is used to take measurements.
An aneroid barometer uses a flexible metal bellows instead of mercury to measure air pressure. The tiny accordion-like sealed cylinder shrinks and expands with changing air pressure. An attached pointer or pen indicates the amount of change on an attached scale.
Air pressure is measured in a number of different units. It can be measured in units of weight per unit of volume, like pounds per square inch or kilograms per square centimeter. However, the convention with American meteorologists is to refer to barometric pressure in simply "inches," which in fact means inches of mercury on a mercury barometer — even if the pressure was measured on a different kind of barometer. In other parts of the world air pressure is recorded in a standard metric measurement of pressure, called millibars. Yet another variation is the kilopascal, which is millibars divided by 10. An air pressure reading of 29.92 inches (of mercury) = 1013.25 millibars.
You can measure and track changes in atmospheric pressure with this easy-to-make barometer. It works like an aneroid barometer.
* empty coffee can or wide-mouthed jar
* large balloon
* duct tape
* clear tape
* 2 drinking straws
* empty half-gallon jug or carton
1. Cut the neck off of a large balloon. Stretch the balloon top tightly over the can or jar. Use duct tape to secure it to the can or jar. It needs to be an airtight seal!
2. Attach two drinking straws together by pinching one and inserting it into the end of the other. They should overlap at least an inch. Tape the toothpick to one end of the combined straws so it sticks out a half inch or so (1 cm) from the end of the straws. This will be the barometer's indicator needle.
3. Lay the non-toothpick end of the combined straws on top of the balloon-covered can or jar. The end of the straws should be in the center of the balloon-covered top. Use a single strip of clear tape to attach the straw onto the balloon rubber.
4. Trace or photocopy the barometer scale below, or create your own.
5. Set the carton or jug behind the toothpick end of the straw. Tape the scale onto one side of the carton or jug.
6. Set your barometer indoors in a still area where the temperature doesn't change. Don't set it in a sunny window or a drafty spot. (Note: This kind of barometer's readings are affected by temperature, which is why it must be kept in a temperature-stable place in order to get the most accurate readings.)
7. Let the barometer sit for a number of hours before taking a first reading. The toothpick will rise and fall as changes in air pressure contract and expand the balloon, moving the straw. You can create a chart with the following headings to record the air pressure over time: DATE, TIME, READING, WEATHER (Sunny, Cloudy, or Rainy?).
Hurricanes are the planet's largest storms. Hurricanes are usually 300 miles (480 km) in diameter and can have wind gusts in the 150 to 200 mph (240 to 320 km per hour) range. They start in the band of warm water near the equator when the ocean is at its warmest. (Hurricane season is June through November for North America and the Caribbean.)
Warm water of 80°F (27°C) or more is the needed fuel for these giant storms. The moisture from the warm water evaporates into the air hanging above it. This creates warm, moist, low-pressure rising air. As this air moves upward, it cools, and its water vapor condenses into clouds and rain. In order for water vapor to change to liquid water, a tremendous amount of heat must be released. This released heat in turn warms up the surrounding air, causing it to rise faster and create even lower pressure at the surface. Outlying higher-pressure air rushes into the new low-pressure area as fast-moving updrafts and eventually a huge whirling mass of air called a tropical depression can form. If the depression continues to be fueled by the engine of heat and low pressure of warm water, it's classified as a hurricane once its winds have reached 74 mph (119 km per hour).
A hurricane's strength is determined by just how low its pressure is. The lower the pressure, the faster and stronger outside air rushes in toward it, so the faster the winds. The low pressure also causes the sea level below the storm to rise, which becomes a flooding mound of water — called a storm surge — if the hurricane hits land. Flooding from storm surges and heavy rain, like in 2005's Hurricane Katrina, causes more hurricane deaths than winds. Hurricanes are rated on the Saffir-Simpson scale of 1 to 5 (see page 15). The scale shows how these storms strengthen as their pressure drops.
In this activity you can model the shape and pattern of a hurricane's winds and clouds — using water instead of air.
* shallow cake pan
* food coloring
paper and pencil (optional)
1. Fill the cake pan half full with water and stir a few spoonfuls of cornstarch into it until it looks milky.
2. When the water is more or less still, add one or two drops of food coloring into the center of the pan. Watch how the color sinks and moves.
3. Next, pull the spoon very slowly through the water. Watch for the trail of small spirals that form behind the spoon. You can draw the patterns, if you want.
4. "Erase" the color by thoroughly stirring the mixture and then letting the water settle again.
5. Add two or three more drops of food coloring in the center. This time use the handle of the spoon to make a circle around the drops. Compare it to the hurricane picture on page 13. You can draw the pattern, if you want.
Ozone Layer Depletion
About 12 to 30 miles (19 to 48 km) above the earth, near the top of the stratosphere, is the protective ozone layer. The layer is a band of ozone gas molecules, each made up of three oxygen atoms (O3). The kind of oxygen gas you breathe has only two oxygen atoms (O2). Ozone gas is created by the powerful sunlight at this altitude. Strong rays from the sun break up regular oxygen into single oxygen atoms. These lone oxygen atoms combine into triple-oxygen ozone, and then later break down again into regular oxygen (O2). While oxygen is continually recombining like this, the ozone absorbs some of the sun's ultraviolet (UV) light. This UV absorption shields the earth from the full force of its harmful effects. Too much UV light can cause skin cancer and eye cataracts, and can damage plants and plankton.
In the late 1970s, scientists began to notice a thinning of the ozone layer over Antarctica during its frigid early spring. This soon-named "hole" in the ozone layer was carefully studied and researchers quickly realized that in fact ozone was thinning over both poles — arctic and Antarctic. The cause was chlorofluorocarbons (CFCs), super stable chlorine-containing chemicals. CFCs were used in air conditioners and refrigerators, as propellants in spray cans, in cleaning solvents for electronics, and to make disposable cups and other foam products. CFCs are so stable that once in the air they rise all the way to the stratosphere before they break down. When powerful sunlight in the stratosphere breaks up the CFCs, their chlorine destroys protective ozone. One CFC molecule can destroy up to 100,000 molecules of ozone. The chlorine destroys so much ozone that the ozone layer thins, letting more dangerous UV light through to the earth.
The United States, Canada, Norway, and Sweden banned the use of most CFC-based spray-can propellants in 1979. And the Montréal Protocol treaty of 1987 set in motion the phase-out of all CFC production. It has since been signed by 183 nations. Today the rate of ozone layer destruction is slowing. And scientists believe the ozone layer can repair itself given enough chlorine-free time. But it will likely take another 50 years for the ozone layer to return to normal.
Screening out the Sun
The layer of upper atmospheric ozone gas screens out a good deal of harmful ultraviolet light, preventing it from reaching the earth's surface. In this activity, you can test the sun-blocking effects of a number of filters.
Excerpted from Weather Projects for Young Scientists by Mary Kay Carson. Copyright © 2007 Mary Kay Carson. Excerpted by permission of Chicago Review Press Incorporated.
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