How Are Weather Data Collected?

Transcription

1 1.2 Investigate 1.2 Build How Are Weather Data Collected? The details of the weather in the different regions of the United States show the wide range of events that can take place in the atmosphere. Meteorologists use weather stations set up around the world to collect weather data. The data allow meteorologists to make predictions about the weather. Five tools are always part of a weather station: a rain gauge, a thermometer, a barometer, an anemometer, and a wind vane. The tools scientists use for collecting weather data can be very complicated. You can build simple versions of these instruments, however, to collect useful weather data. You can build some of these instruments with materials you have around your home. Your group will work together to make these tools and build a weather station. Each group member will build one or more of these tools, and then you will work with your group to determine where you want to place your weather station to collect weather data. Once you determine good places to take the measurements, you will collect weather data for several days. These data will tell you about the weather and perhaps make it possible for you to predict changes in the weather. Conference Before you get started, work with your group to plan your weather station. The text on the next few pages describes the tools in a weather station and how to build simple versions of the tools. Decide who in your group will build each tool. The group member or members assigned to each tool will build that tool and report to the group about what the tool measures, why it is important to take those measurements, and how the tool works. Record your decisions on a Planning a Weather Station page. You will do some more planning after you build the tools. Be prepared to teach your group how to use the weather tool you are building. WW 21

2 Learning Set 1 What Is Weather, and How Is It Measured and Described? rain gauge: a tool used to measure precipitation. In the United States, precipitation is usually measured in inches. How Do Scientists Measure Precipitation? Precipitation is water that falls to Earth in the form of rain, snow, sleet, or hail. Measuring the amount of precipitation is important. For example, if people know the amount of rain that has fallen, they will know whether a river is likely to rise and cause floods. The amount of rainfall is also significant to farmers. Decisions about when and what to plant and when to water fields or harvest crops rely on rainfall measurements. In cold climates, road crews need to know how much snow may fall so they can schedule their shifts, and can order enough supplies and equipment for snow removal. A rain gauge is a simple tool used to measure the amount of precipitation. It is usually a tube with 1-inch markings on the outside. As water collects in the tube, the amount of water can be read using the 1-inch markings. The rain gauge needs to collect precipitation, therefore the tube must be put outside in an open place. To measure precipitation accurately, you will need to place the rain gauge in an area that is open to the sky. You measure rain by recording where collected water reaches on the ruler. If the participation is in the form of snow, sleet, or hail, empty the jar into another container that has the same size diameter and let the frozen precipitation melt. Measure the melted amount in inches. This rain gauge is placed outside in an open area. You determine the amount of rain that has fallen by reading the marks on the outside of the tube. Project-Based Inquiry Science WW 22

3 1.2 Build Assemble the Rain Gauge Tape a ruler onto the outside of a straight-sided jar. Make sure the ruler s 0 line is lined up with the bottom of the jar. A simple rain gauge, placed in an area that is open to the sky, can be used to measure all types of precipitation. Materials ruler straight-sided (cylindrical) jar tape How Do Scientists Measure Air Temperature? Temperature is a very important weather factor. The air temperature outside will determine what clothes you need to wear when you go outdoors. Temperature also determines the types of activity that you can take part in outdoors. A sudden drop in temperature can cause wet roads to turn icy and make driving dangerous. During a growing season, a drop in temperature below freezing can damage farmers crops. Extremely high temperatures can be dangerous to the health of people, plants, and animals. People and animals can die from heat stroke. To measure temperature, scientists use a thermometer marked with a temperature scale. On the Fahrenheit (F) scale, 32 F represents the freezing point of water and 212 F represents the boiling point of water. On the Celsius (C) scale, water freezes at 0 C and boils at 100 C. Because numbers have different meanings depending on the scale you use, you will need to remember to include units (either C or F) with temperature data. If you say 37 without including a unit, you may confuse people. For example, if you are referring to 37 F, it is cold outside. But if you are referring to 37 C, it is very hot outside (over 90 F). In the United States, temperature data are usually given in degrees Fahrenheit. WW 23

4 Learning Set 1 What Is Weather, and How Is It Measured and Described? surface temperature: air temperatures measured around 1.25 m to 2 m (4 ft to 6.5 ft) above the ground. Materials duct tape milk carton scissors stick (2 m) string (10 cm) thermometer Air temperature can vary depending on distance above the ground. So that measurements can be compared, scientists measure surface temperature, the air temperature around 1.25 m to 2 m (4 ft to 6.5 ft) above the ground. The standard way to install a thermometer in a weather station is to put the thermometer in a shelter to protect it from wind, direct sunlight, and moisture. Meteorologists place the thermometer as far away as possible from parking lots, roads, and pavements. These areas can heat up during the day and raise the temperature of the air around them. Sheltering the thermometer from the Sun and keeping it away from paved areas (by at least 30 m, or about 100 ft) helps meteorologists record air temperatures as accurately as possible. A thermometer shelter protects the instrument from wind, direct sunlight, and moisture. Inside the shelter, air can circulate freely around the thermometer and any other instruments. Assemble Your Thermometer Shelter 1. Carefully cut several small holes (approximately the size of quarters) in the sides of the carton or box. This will allow air to circulate. 2. Make a hole with a pencil point in the top of the box. 3. Pull a piece of string through the hole and make a knot in the end that is outside the box. Make the knot big enough so it will not slip back through the hole. A simple thermometer shelter. 4. Mount the box on the stick with duct tape. 5. Secure the thermometer to the string so it is suspended inside the box. Project-Based Inquiry Science WW 24

5 1.2 Build How Do Scientists Measure Air Pressure? When you looked at the weather data in the previous section, you may have noticed that changes in air pressure occur when there are changes in weather. What is air pressure? Air pressure is a measure of the force per unit area exerted by the weight of a column of air above that surface. This column of air extends all the way up to the top of the atmosphere. When air pressure is high, the air in the column above that surface has a greater mass than when air pressure is lower. When air pressure is low, the air in the column has less mass than when air pressure is higher. High pressure usually results in sunny weather with clear skies. If the air pressure is low, rainy or stormy weather is usually coming. Although meteorologists talk about air pressure as high or low, the differences between the two are extremely small. You cannot feel these differences. However, even slight differences in air pressure can have great effects on the weather. You can measure air pressure with a tool called a barometer. One type of barometer is a mercury barometer. Mercury is a liquid metal. A mercury barometer consists of a long, thin, glass tube closed at one end filled with mercury. The open end of the glass tube is inverted in an open dish of mercury. When air pressure is high, the mass of the air pushes down on the mercury in the open dish more than it does when the pressure is lower. This forces the mercury up the tube, and the level of the mercury rises. As air pressure decreases, the air does not apply as much force on the mercury in the dish. This allows the mercury in the tube to fall. The distance the mercury rises or falls in the tube can be measured. Recall that distances can be measured in centimeters or inches. In the tables you looked at in the last section, air pressure was reported in inches of mercury. This mercury barometer indicates differences in air pressure. As air pressure rises, the mass of the air pushes down on the mercury in the open dish more than it does when the pressure is lower. This forces the mercury up the tube, and the level of the mercury rises. liquid: matter that has a definite volume but not a definite shape. A liquid takes the shape of its container. The particles remain close together and slide past one another in a fluid motion. WW 25

6 Learning Set 1 What Is Weather, and How Is It Measured and Described? calibrate: to standardize a measuring instrument by comparing it with an accepted model. Another type of barometer, an aneroid barometer, is made of an airtight metal box from which most of the air has been removed. The box becomes squeezed as air pressure around it increases. The box expands as air pressure decreases. Levers attached to the box transfer this movement to a needle. The needle moves to the corresponding air-pressure measurement on the face of the barometer. The scale on these barometers is usually calibrated in inches of mercury. An aneroid barometer does not use a column of fluid. Instead, it uses a hollow metal disk containing very little air. A change in air pressure changes the thickness of the disk. This in turn moves a needle on a dial. Mercury is poisonous and cannot be used in the classroom. Therefore, you will build a barometer using another liquid, water. You will use a jar and a straw to construct your barometer. You will measure differences in air pressure by comparing the levels of the water in the straw from one day to the next. As air pressure increases, the level of the water in the straw will rise. As air pressure decreases, the level of the water in the straw will fall. Changes in air pressure usually happen several hours before the weather changes. Noting changes in air pressure can help you predict changes in weather. Project-Based Inquiry Science WW 26

7 1.2 Investigate 1.2 Build Barometers can be mounted inside or outside, because changes in air pressure are the same in both places. You will need to place your barometer in a place where it is unlikely to get knocked over, and where the temperature will remain fairly constant. If you record the water level on the day you make your barometer, you will be able to determine how changes in air pressure match changes in weather. Assemble Your Barometer 1. Put some water into a jar so that it is less than half full. Add some food coloring to make it easier to see the height of the water. 2. Put the straw into the jar and tape it to the inside. The bottom end of the straw should be in the water, but not touching the bottom of the jar. 3. Suck the water halfway up into the straw. Pinch the straw to trap the water. The height of the water in the straw must be above the height of the water in the jar. Try not to get the water into your mouth. 4. When you take your mouth off the straw, keep pinching it while you put a piece of modeling clay over the top of the straw to seal it closed. The water should stay in the straw. If it does not, start over and make sure to seal the straw well with the clay. Materials small jar clear drinking straw food coloring small piece of clay tape index card 5. Develop a method of recording changes in the level of the water in the straw. You could attach an index card onto the outside of the jar and mark it each day. Or you could put an elastic band around the jar and move the band up or down each day to show the level of the water in the straw. Each time you measure, record the level of water in the straw and the date. Be sure that the jar and water are clean and use a new, clean straw. You can build a simple barometer with a drinking straw and water in a jar. Record the weather on the day you make your barometer to check if the air pressure is rising (going up), falling (going down), or steady (staying the same). WW 27

8 Learning Set 1 What Is Weather, and How Is It Measured and Described? anemometer: an instrument used to measure wind speed. How Do Scientists Measure Wind Speed? You might have noticed that the speed of the wind increases as a thunderstorm approaches. You can recognize the change in wind speed by observing leaves fluttering in the trees, flags flapping, or waves on the water getting bigger. Meteorologists also observe wind speed to help determine changes in the weather. To a meteorologist, a strong wind is an indication that the weather may be changing. The speed of the wind affects daily life and meteorologists must inform the public about wind speeds. High wind speeds can be dangerous for boaters and airplane pilots. Very high wind speeds during storms can topple trees and tear roofs off buildings. However, wind is needed to turn windmills, fly kites, and sail boats. Meteorologists use a tool called an anemometer to measure wind speed. One common type is called a cup anemometer. The cups are pushed by the wind, and they turn as the wind pushes them. As the wind blows harder, the cups turn faster. Anemometers need to be mounted out in the open in the wind. Wind-speed readings can be changed easily depending on where the anemometer is mounted. Think about a time when you have walked through a narrow place, such as an alley or outdoor mall, and the wind was blowing very hard. If you put the anemometer in an alley or between buildings, you will be measuring the wind in that small space. This information is not as useful as a reading that you could take in a field or on top of a building where the wind might be changing for other reasons. A cup anemometer is used to measure wind speed. The cups spin as they are pushed by the wind. The harder the wind blows, the faster the cups go around. Project-Based Inquiry Science WW 28

9 1.2 Build Assemble Your Anemometer 1. Cut the rolled rims off four of the small paper cups. Number them 1 to Using a one-hole paper punch, make a hole in each cup. Make the hole about 1.5 cm from the top of the cup on one side only. 3. Take Cup 1 and one straw. Push one end of the straw through the hole in the cup to the opposite side. Bend about 1 cm at the end of the straw and staple the bent end to the inside of the cup. Repeat with Cup 2 and the second straw. 4. Place an easily visible sticker, decal, or piece of colored tape on the side of one of the cups to make it easy to count the spins. 5. Take Cup 5 and punch 4 equally spaced holes about 1.5 cm from the top. This cup will go in the center of the anemometer. With the pencil point, carefully poke a hole in the center of the bottom of this cup. 6. Take the free end of the straw attached to Cup 1 and push it straight through two holes in Cup 5, as shown. Repeat with Cup 2 and the second straw. Once both straws are pushed through the holes, attach Cups 3 and 4 with staples as in Step 3. All four cups should open in a clockwise direction, as shown. Materials 5 small paper cups scissors 2 straight plastic straws pencil with eraser one-hole paper punch stapler ruler sticker or decal pushpin modeling clay 7. Carefully push the pushpin through the straws where they cross in the middle of the center cup. Push the pin all the way through the straws so that the point sticks out the bottom. 8. Slide the eraser end of the pencil up through the hole in the bottom of Cup 5. Push the pin into the eraser. Be sure the cups can spin freely. Push the end of the pencil into a small ball of clay as a base. 9. To read your anemometer, hold it up to the wind. Have a teammate time 30 s as you count the number of complete turns. Use the cup with the sticker to help you keep count of the complete turns. If placed in an open area, this anemometer will measure how fast the wind is. WW 29

10 Learning Set 1 What Is Weather, and How Is It Measured and Described? wind vane: a tool for measuring wind direction. A wind vane pivots to point in the direction from which the wind is blowing. How Do Scientists Measure Wind Direction? Wind direction, along with wind speed, helps meteorologists understand the movement of weather patterns in a given area. Sometimes a change in wind direction indicates a weather change, such as a severe storm approaching. If meteorologists can tell people the speed and direction of the wind, they may be able to save lives in the case of severe weather approaching. Also, around large lakes, wind direction is a very important factor in the winter before the lakes are frozen. The direction of the wind determines which areas around a lake will receive the greatest snowfall. Wind direction is reported as the direction from which the wind is blowing. Wind direction is given using compass points north, east, south, or west. It is also sometimes measured in degrees where 360 degrees is north, 90 degrees is east, 180 degrees is south, and 270 degrees is west. Wind vanes are used to measure the direction of the wind. The weather vane has an arrow or pointer that moves to point in the direction of the wind. A weather vane pointing north indicates that the wind is blowing from the north to the south. A wind vane, like an anemometer, is mounted at the top of a pole so it can turn easily in the wind. It needs to be placed out in the open on top of a house or barn, or in a field. This is because, in an enclosed space, wind speed and direction can be affected by walls or objects in the space. The wind speed and direction in a closed space are different from wind speed and direction out in the open. Project-Based Inquiry Science WW 30

11 1.2 Build Assemble Your Wind Vane 1. Trace the triangle pattern two times onto the poster board. Then, trace two more triangle patterns about one fourth the size of the first two. Cut the four triangles from the poster board. This will be the tail of your wind vane. 2. Put one triangle on the table and lay the drinking straw on top of it. The straw should extend about halfway into the triangle in the middle of one side. Follow the diagram for this part. Tape the straw to the triangle. 3. Sandwich the straw between the two triangles by putting the second triangle on top of the straw. Carefully line up all the edges of the two triangles. 4. Tape all three edges of the triangles together, covering the straw. (Repeat Steps 3 and 4 for the second set of triangles patterns.) 5. Find the place where the straw balances by putting the straw on your finger so it sits on your finger without tilting or falling. This point will be close to the triangle. 6. Mark the balance point on the straw with a marker. Materials plastic drinking straw tape file folder marker triangle pattern new pencil with a new eraser one straight pin scissors modeling clay 7. Hold the straw so that the back edge of the triangle is pointing up and down. At the balance point, stick the straight pin from the topside, down through the straw, so that it pokes all the way through. 8. Push the pin into the center of the eraser at the end of the pencil. Make sure that the straw spins smoothly around the pin. 9. Push the point of the pencil into the ball of clay and secure the clay to a fl at surface. To find the direction of the wind, you have to find north, south, east, and west in the location where you are going to place the wind vane. You can use a compass to do this. When the wind vane turns in the wind, it will indicate which way the wind is coming from. A south wind will be coming from the south and that is the direction that the free end of the straw will be pointing. Once you determine the directions with a compass, you can use the wind vane to indicate which way the wind is coming from. WW 31

12 Learning Set 1 What Is Weather, and How Is It Measured and Described? Conference When you finish building your weather tools, return to your group. With your group, you will decide where to place your weather station. You may place it somewhere around the schoolyard, or you may decide to place it in the neighborhood. You will have to choose a safe place for your weather station. You will also have to choose a place where you can take accurate measurements using the tools. To decide where to place your weather station, everyone in your group will need to know what each tool measures and how it has to be placed to take good measurements. That means you will have to teach the others in your group about the tool you built. For each tool, the person or people who built that tool should report these things to the group: what the tool measures why it is important to take those measurements how the tool is used where the tool should be placed to collect accurate and consistent data Then, based on these reports, decide where you want to locate the weather station to collect accurate data. Record your decision on your Planning a Weather Station page, and record the reasons you will collect your data from that location. Now discuss how to read the instruments. It is possible that two different people could read the same weather tool differently. Decide on steps you can take to make sure everyone in the group reads each tool the same way. Record these steps on your Planning a Weather Station page. Project-Based Inquiry Science WW 32

13 1.2 Build When you have decided where to place the weather station and how to read the tools, work together with your group to answer these questions. Record your answers, and be prepared to share them with the class. 1. How did you decide on the location for each tool? To do this, you needed to know what each tool measures and the best placement for each tool. Share this information with the class. 2. Which tool or tools were the most difficult to place? Why? 3. How did you decide the best way to read each weather tool to collect accurate data? Share your steps for reading each tool with the class. Communicate Share Your Ideas Discuss answers to the questions above as a class. Then discuss where you will place your weather stations and why and how to take good measurements. If you think a group could do a better job of placing their weather station or taking good measurements, respectfully offer your ideas. Collect Your Data For five days, you will use your weather tools to collect and record weather data. When it is your turn to measure, follow the instructions your group developed for reading the weather tools accurately, and record your data on your group s Weather Data page. Each member of the group should also keep a weather journal. Record your observations of the weather in the morning, around noon, and in the early evening. Later, you will share your weather journal with your group and enter this information on a Weather Data page. WW 33

14 Learning Set 1 What Is Weather, and How Is It Measured and Described? Stop and Think 1. How are the tools you have built like the weather tools meteorologists use? How are they different? 2. How do you think the measurements you are making are similar to those meteorologists make? How are they are different? Why? 3. One of the important reasons for recording weather data is to predict the weather. Describe one time when knowing what the weather would be made life easier for you. What measuring tool do you think would have been the most helpful for making this prediction? How Meteorologists Gather Weather Data The tools that you built are simple versions of the same tools that meteorologists use every day. Look at the photo of the weather station. Can you find the wind vane, the anemometer, and the box that houses the thermometer? One difference between your observations and the observations that scientists make is the way the data are collected. You are reading each instrument and recording the data on paper. Scientists usually use computers to read and record data. This means that information can be collected all day and all night. Then meteorologists can use computer programs to analyze the data and make weather predictions. Project-Based Inquiry Science WW 34

15 1.2 Build What s the Point? Meteorologists use many different tools to collect weather data. The tools in actual weather stations have the same names and functions as the simple tools you constructed in this section, but scientists use tools that are more complicated and provide more precise data. To make good weather predictions, meteorologists must collect data in exactly the same way each time. For example, a rain gauge is used to measure the amount of precipitation that has fallen in an area in a certain amount of time. To collect accurate data, the rain gauge must be protected from wind. If strong winds blow over the top of the gauge without falling into it, the measurement of precipitation will not be accurate. Instruments need to be designed and placed to eliminate these types of problems. All of the tools discussed in this section provide important data needed to understand and predict weather. Knowing the amount of precipitation, the temperature, the wind speed and direction, and the air pressure allows meteorologists to make helpful weather predictions. The information meteorologists provide can save lives, protect homes and businesses, and keep livestock and crops healthy. South Pole meteorologists prepare to launch weather balloons at Amundsen-Scott South Pole Station. WW 35