4DA-03PA COOPERATIVE EXTENSION SERVICE UNIVERSITY OF KENTUCKY—COLLEGE OF AGRICULTURE Variables Kentucky 4-H Weather Project Unit III Tom Priddy, Extension Agricultural Meteorologist

AGRICULTURE & NATURAL RESOURCES • FAMILY & CONSUMER SCIENCES 4-H/YOUTH DEVELOPMENT • COMMUNITY & ECONOMIC DEVELOPMENT Weather Variables Introduction In this unit of the 4-H weather Contents project, we will be looking at and de- Introduction ...... 2 scribing how to measure the Objectives ...... 2 different elements that make the Activities ...... 2 weather. These elements, such as air , speed and direc- Temperature tion, and , are normally Why Kentucky Vary ...... 3 called the weather variables because Activity: Making an Accurate Gauge ...... 3 each element changes with time, yet are all related. We’ll look at these re- lationships and forecasting in detail in Making a Weather Vane ...... 4 Unit IV. Thar’ She Blows ...... 4 First, let’s learn about temperature Where the Winds Come From ...... 4 as a weather variable. Why Our Winds Blow from West to East ...... 5 Kentucky Breezes and Winds ...... 6 Objectives How Fast Is the Wind Blowing ...... 6 • Learn how temperature changes Experiment: Making a Cup ...... 6 affect other weather conditions. The Beaufort Scale for Measuring ...... 7 • Learn how wind patterns affect the weather. • Learn why humidity is one of the Understanding in the ...... 8 weather variables. 100% Relative Humidity or Saturated Air? ...... 8 The Hair ...... 8 Building a Hair Hygrometer ...... 9 Activities • Make a . Summing Up • Give a weather demonstration. What’s Next? ...... 9 • Exhibit a weather station at the Talks & Demonstrations...... 9 county fair. Citizenship & Leadership Activities ...... 9 • Submit project records and weather observations. Observation Sheets ...... 10 Weather Variables Record Sheet ...... 12

2 Temperature

One of the first questions we ask and the funnel, you have made a shield about the weather is, “What is the tem- that will prevent evaporation and help perature?” In Unit I, you learned how you to make more accurate readings. to keep temperature readings, and in Now, you are ready to take read- Unit II, you continued to keep those ings. Measure the precipitation with a readings. But just what do these read- plastic ruler just as you did before. Re- ings mean? Temperature affects all member to pour out the precipitation other weather conditions. Without after each reading so your next read- changes in temperature, there would ing will be accurate. (You will be keep- be no changes in , wind, or ing records of the precipitation for humidity. three months.) A general rule is to For this project, you can use the measure precipitation to the nearest same thermometer you used in Units tenth of an inch. (What other units of I and II. If you need a new thermom- measure could you use? Hint: MM). eter, many feed stores and farm-re- Comparing your reading with the lated businesses give them away free, weather news will help you learn to or you may want to purchase an inex- be more accurate. You may wish to pensive one. Put the thermometer in devise a holder for your rain gauge your weather shelter where it will be and mountains. These differences in so it will not blow over. Keep your rain out of direct sunlight and yet will have the terrain can readily influence gauge on top of your weather station air circulating around it. weather changes. The Appalachian (see Figure 1). Mountains are located in the North- east, Quicksand, and Wilderness Trail Why Kentucky areas. As weather moves from the Temperatures Vary western sections of Kentucky, the air must rise to travel across the moun- Have you ever participated in tains. As the air attains a higher alti- 4-H events with 4-H’ers from a tude, the temperatures cool. Not only different part of the state? In Kentucky, does this produce a temperature 4-H’ers compete on local, county, area, change but also helps to create rainfall. and state levels. Perhaps when you went to 4-H camp or attended Ken- tucky 4-H Week in Lexington, you had Activity: Making an the opportunity to talk to members funnel from many different 4-H areas. Did Accurate Rain you know that their weather may dif- Gauge candle wax fer from yours? Watch the TV weather In Unit II you learned how to use a brief for one week and record the daily simple rain gauge. For this unit, you will high temperature near your location improve your rain gauge to make it and one other location across the more accurate. First, check your old rain plastic disc state. Discuss these differences in the gauge. Make sure the paint has not temperature readings. One reason chipped and the can will not rust. Sec- temperature varies throughout Ken- ondly, cut a circle of plastic foam that tucky is that our latitude varies. The far- will fit inside the can snugly. Now, ther one travels north, the cooler the make a hole in the middle of the plas- tin can temperature will be. tic large enough for the end of the fun- Another major reason for air tem- nel to be placed. The funnel must be perature differences in Kentucky is the the same diameter (distance across wide variety of terrains. In the Blue the top) as the can. Why is this so? Grass and Fort Harrod areas, the land (Hint: Compare the area of the top of is fairly flat. In comparison, the east- the funnel to that of the can.) Put the ern portion of the state has many hills funnel in place. By adding the plastic Figure 1. Advanced rain gauge.

3 Winds

Long before weather vanes or wind-measuring instruments had been thought of, early weather watch- ers recognized that wind direction was important. They didn’t understand why, but they knew that wind from one direction generally brought fair skies while wind from another direction brought rain. So they watched the trees sway for a sign of the wind direction.

Making a Weather Vane Today we have better ways of de- termining wind direction. A sensitive Figure 2. Weather vane. weather vane can be constructed fairly easily. You will need a piece of wood for an arrow about 12" long, ½" • Winds from the west, southwest, stant heat forms a low pressure belt thick, and 3" wide; a mounting stick; a and south bring fair and warmer of rising air known as the Doldrums. ¾" by 1' board; a nail or screw for at- weather. They blow from warmer According to Figure 3, as air rises taching the arrow to the mounting lands. from the Doldrums, it cools and drifts stick; and two washers (see Figure 2). • Winds from the east, southeast, toward the poles. Some of it falls in the Draw an arrow like the one shown. and northeast generally bring Horse Latitudes, around the 30° lati- Then, cut the arrow out of the wood. rain. They blow in from the ocean. tude, and piles up to create a belt of You may ask your leader to supervise. In Kentucky, the most common high pressure. The constant pressure Find the point where the arrow is wind direction is from the south. How- of the Doldrums and the Horse Lati- equally balanced by steadying it on ever, during February and March, tudes makes these regions of calm or your finger. This is the balance point. northwesterly winds are common. For very light winds. But in between them, Drill a hole at that point through the the next three months, you will be re- air is on the move. Rushing from high shaft of the arrow. Paint the weather cording the wind direction. pressure to low pressure, the air flows vane white to match your weather sta- back toward the equator as the strong tion. Now, you are ready to attach the Where the Winds and steady northeasterly Trade Winds. weather vane to your weather station. Some of the air that rises from the Be sure one side of the mounting stick Come From equator continues on to the poles. faces north. Label the stick with the Wind is caused by air moving from There it sinks, becomes compressed, compass points—north, east, south, a high pressure to a low pressure area. and rushes out toward the 60° latitude. and west—ensuring that north on the Whether the wind is a small gust play- These icy blasts from the poles are stick points to the north. fully whirling up dust in the cornfield the Polar Easterlies. If these icy or a great wind of force, the winds dip into the middle latitudes, Thar’ She Blows cause is always the same. Air that is they can bring to Florida. The As you observe the wind for under pressure is trying to escape or rest of the winds, between the Horse direction, you may start to notice a balance itself and heads for the Latitudes and the Polar Easterlies, are special wind pattern. Here are a few nearest area of lower pressure. If the blown back toward the poles. These patterns that apply to many parts of difference in the high and low are called the Prevailing Westerlies. the United States. See if it holds true pressure is great, the wind will be They control the major wind currents to where you live. strong. If the difference is slight, the for the United States and Europe. • Winds from the north, northwest, wind will be light. Equator Doldrums are caused by and west generally bring dry and The sun sets the stage for the world’s warm air rushing over the equator cooler weather. They blow from great winds. At the equator, where the area. Sailing ships often went on for cooler masses of air to the north sun shines constantly each day, warm days and days in this region without and drier masses of air to the west. air rises in a mighty stream. The con- so much as a breeze of wind to fill

4 fewer miles around. The equator must move faster than the poles to main- tain the one rotation per 24 hour mo- tion. Let’s see how these different rates of rotation change the nature of our winds. You will need an old phonograph record, a turntable, and a piece of chalk. Place the record on the turn- table spindle. Now, pretend the cen- ter hole is the North Pole and the outer edge of the record is the equator. Take the phonograph record and rotate it counter-clockwise on the spindle. This represents the way the earth turns as seen from the North Pole. With a piece of chalk, try to draw a straight line from the spindle to the edge of the record while the record is in motion. What happens? All you can draw is a curve, Figure 3. Earth’s wind circulation as in Figure 4. pattern. This is called the Coriolis Effect. their sails. Heavy rainfall, ty- would cool down and sink. The pres- Our winds move just like the chalk line. phoons, and hurricanes are typical for sure of this sinking cool air would force Winds coming in from the north curve this region. surface air toward the equator at an to the right. From south, the winds Trade Winds are so named be- even speed. This could drastically al- curve to the left. cause many years ago sailing ter our normal weather patterns. vessels traveled the seas carrying However, we know the earth ro- Kentucky Breezes cargo, and the winds of this region tates. It takes 24 hours for the globe aided them in transporting their goods to make one complete turn. At its wid- and Winds Kentucky has a number of lake and to other trade centers. The skies are est point, the equator, the earth is ap- mountain areas. The varied tempera- mostly clear in this area. proximately 25,000 miles around. The tures of these geographical locations The Horse Latitudes are a very earth rotates eastward at 1,000 miles can affect the air current of these calm, warm region. Winds there are per hour. At locations north or south places. For example, there is almost very weak. The skies there are clear. of the equator, the earth becomes Sailing ships carrying horses to the new world were often delayed in this area because of the lack of wind. The story goes that when food for the ani- mals ran out, the animals starved to death and were thrown overboard. The Prevailing Westerlies control the major air flows in the United States. If interference from polar fronts did not occur, the United States would have fair weather with clear skies and occasional .

Why Our Winds Blow from West to East What would happen if the earth were not rotating? We already know that warm air rises. If the earth stopped spinning, the warm air would rise to the poles. There, the warm air

5 to close the ends where the spouts were cut off with liquid solder. Con- struction details for the rest of the as- sembly are about the same regardless of the cups used. 1. Punch holes on opposite sides of the cups so that dowel rods fit tightly through them. Then, po- sition as shown in the illustration and fasten with waterproof glue. 2. Make the hub assembly by us- ing a small bottle lid about 1½" to 2" in diameter. The lid Figure 4. The Coriolis Effect. from an ink bottle or other small jar will work very well. Punch or always a breeze at Kentucky Lake. Do pencil or pen cap, one metal lid 1¾" drill three equally spaced holes you know why? It blows one way dur- to 2" in diameter, one small washer in the rim of the lid to receive the 3 ing the day and the opposite way at /8" in diameter, one 3" nail, waterproof cup spokes. Punch another hole night. During the day, the land heats heavy-duty glue, paint, and liquid sol- in the center of the top. Glue a faster than the water. Cooler, heavier der (see Figure 5). ballpoint pen cap into this hole air from the water blows toward the Wind speed is often measured by as shown. land. At night, the land cools faster a cup anemometer. There are many 3. Glue a small washer over the than the water. The cool, heavier land ways to build an anemometer of this opening of the pen cap. air blows toward the lake. kind. Cups can be made using either Have you ever been to the top of funnels or gelatin molds. If small fun- Black Mountain, Kentucky’s highest nels are used, it might be necessary peak? If you have, you may have won- dered about another special set of winds. During the day, these winds blow up the mountain. At night, they come whistling down. Can you figure out why? (Hint: Warm air rises upslope during the day; at night, cool air sinks.)

How Fast Is the Wind Blowing? The speed of the wind tells us how great the pressure difference is be- tween two masses of air. To measure wind speed, we can use a scale set up by Admiral Beaufort of the British Navy in 1805. (See the Beaufort Scale for Measuring Wind Speed on the next page.) However, to make our weather station more complete, we can build an anemometer to measure wind speed.

Experiment: Making a Cup Anemometer You will need either three aluminum funnels (2½" in diameter) or three 3 small gelatin molds, three /16" dowel rods (17" long), one metal (or plastic)

6 stretch of road. Have your parent or older brother or sister drive down the road, first at 5, then at 10, and finally at 15 miles per hour while you count the turns it makes in ten seconds. Mul- tiply this number by six to get the num- ber of rounds it makes per minute for 5, 10, and 15 miles per hour. Unless the calibration is made when the wind is not blowing, the procedure must then be repeated going at the same speed in the reverse direction. Then the average of these two measure- ments will give the more accurate cali- bration. The Beaufort Scale below may help you to interpret the readings you take. You will be recording the wind speed for the next three months.

Figure 5. Cup Anemometer.

4. Insert the cup spokes through The anemometer can be calibrated the holes in the rim of the lid until in different ways. One way is to mount the ends touch the pen cap. it on the handle of a broom stick or 5. Glue the cup spokes to the cap other suitable board that can be held and the underside of the washer. out a car window well above the car 6. Paint one cup and spoke a roof while driving along a straight different color.

The Beaufort Scale for Measuring Wind Speed Description Speed (mph) Observation Calm less than 1 Smoke rises straight up. Trees are still. Water is mirror calm. Light air 1-3 Smoke drifts in direction of wind. Leaves on trees move slightly. Light breeze 4-7 Wind can be felt on face. Leaves rustle. Gentle breeze 8-12 Leaves in constant motion. Light flags flap. Moderate breeze 13-18 Small branches move. Dust is stirred up. Fresh breeze 19-24 Young, leafy trees sway. Dust is stirred up in . Crested wavelets on lakes and ponds. Strong breeze 25-31 Tree boughs swing. Wind whistles through telephone wires. Moderate 32-38 Tree trunks swing. Difficult walking against the wind. Fresh gale 39-46 Walking requires effort. Small branches break. Strong gale 47-54 Slight damage to buildings, signs, and windows. Whole gale 55-63 Trees are blown down. Considerable damage to buildings (more often experienced at sea). 64-74 Wide damage (rare). Hurricane 75 or more Great damage, wide destruction.

7 Humidity Understanding further cooling would cause conden- panding, depending on the humidity, sation. The air is said to be completely is the principle by which a very simple Water Vapor in the saturated, and the relative humidity of but accurate hygrometer is con- Atmosphere this air is 100 percent. Any further cool- structed. This word comes from Latin ing would cause precipitation. and means to measure water. In the previous units, you have During the summer months, we Invented in the mid-17th century, learned about humidity in the air— can see this occur almost every day. indicate how damp, or mainly in the saturated state. When In the morning, the puffy cumulus humid, the air is. Earlier, simpler hy- the air is completely saturated, clouds clouds dot the sky. By midday, sun- drometers contained a substance and possibly precipitation occur. Usu- shine heats the earth’s surface caus- that changed drastically with ally these are the only times when ing the air near the surface to warm changes in the amount of moisture many people are aware of moisture and begin to rise. The cumulus clouds in the air. Hair is such a substance. in the air. But even in the coldest air, build vertically into towering cumulus Can you think of other substances moisture, in the form of water vapor, and often into cumulonimbus—the true that are similarly affected? is present. If you’ve ever stripped to- thunderhead (see clouds in Unit II). As the air becomes more humid, the bacco, you can physically feel and see The second process can occur as long strand of human hair in the hy- the effect of humidity in the air; if hu- follows: if the air is near saturation and grometer, shown in Figure 6, midity has been high, tobacco will be a southerly wind is pumping more stretches. This causes the suspended in case. If humidity has been low, the moist warm air into the region, the air penny to slowly drop, and the needle tobacco leaves are brittle and not in will become saturated, and precipita- turns, indicating the relative amount case. tion will occur. of moisture in the air. There are many terms used to de- scribe the amount of humidity in the air. Two of the most commonly used The Hair terms are: Hygrometer Humidity: The amount of water va- What happens to your hair when por in the air. you go swimming? Of course it gets Relative Humidity: The percentage wet, but it also stretches. Now, what of water vapor the air is holding based happens after you blow-dry your hair? on the amount the air can hold at that You get the frizzies! This very simple particular temperature. process of hair contracting and ex-

100% Relative Humidity or Saturated Air? What’s the difference between 100 percent relative humidity as compared with saturated air? The answer: none. Air that is completely saturated has a relative humidity of 100 percent and cannot hold any more water vapor at that temperature. How does the wa- ter fall out of the air? It takes one of two processes for this to occur: 1. By cooling the saturated air. 2. By adding more water.

As moist air rises, it slowly cools. As the temperature drops, the rela- tive amount of moisture the air can hold decreases to a point where any Figure 6. Hair hygrometer.

8 Summing Up weather for your local area with a fair Citizenship & amount of accuracy. Keep records for three months to observe the weather Leadership trends. Activities Give demonstrations and talks 1. Help your leader organize a showing how these instruments work. weather workshop for another Visit a local weather center and see 4-H club or any other appropri- just how predictions are made for the ate group. news media. 2. Prepare posters showing Exhibit your weather station and in- Kentucky’s wind or other struments at the county fair. Include at weather patterns. Use your 3- least one month’s observation with month records to develop these your exhibit. posters. Display them in your Be sure to submit your record book, school or bank or other public including the project story, weather place. observations, photo sheet, and record 3. Serve as a leader for a younger sheets. group of 4-H’ers. Help them with their weather experiments or in What’s Next? any way that you can be of In the next unit, you will learn how service to the group. Building a to read weather maps, how to give a 4. Take a group to visit a weather weather forecast, and how to qualify station, or invite a meteorolo- Hygrometer as a Storm Spotter’s Guide for your lo- gist to talk to your group or To build your own hygrometer, you cal area. another group about weather will need one shoe box, one hair (long instruments. strand), one paper clip, transparent tape, one match stick or broom bristle, Talks & one file card (3" x 5"), one needle, and Demonstrations one penny. Giving a talk or demonstration is an Construct your hygrometer as excellent experience. First, it helps you shown in Figure 6. If the pointer does learn to organize a helpful, logical not move very much, the needle is piece of information to share with probably stuck. What would you do to someone else. Then, it gives you ex- help the needle move more easily? perience in speaking in front of a group. (Hint: reduce friction.) This can be a small or large group. It If, after building a hair hygrometer, also helps your audience by teaching you keep it in your house, what hu- them about weather—possibly giving midity will you measure? Is humidity them information that could save their different inside your home as com- lives. So as you go through this project, pared to outside? If you want to mea- be thinking about what you would like sure relative humidity outside, where to share with a group. should you keep your hygrometer? You may want to do a demonstra- (Hint: Did you build a weather shelter?) tion on how to build some of the YOU DID IT! You have made a ba- weather instruments that you put in sic weather station! You have learned your weather station. Or you may want how to use the basic tools of a me- to help your audience learn about teorologist: a rain gauge, a barometer, weather variables so they can be pre- a thermometer, a weather vane, an pared to predict the weather for them- anemometer, and the Beaufort Scale. selves. Now that you have an understanding of these tools and what they indicate, you can make observations of

9 Date Time Temperature Cover Precip Humidity Direction Wind Speed Prediction Observations Sheet

10 Date Time Temperature Cloud Cover Precip Humidity Direction Wind Speed Prediction Observations Sheet

11 Weather Variables Kentucky 4-H Weather Project Unit III Record Sheet

Name ______Birth Date ______Grade ______Address ______(Street & Number/P.O. Box) (City) (Zip) Name of Club or School ______County ______Number of Years in 4-H ______Current Date ______1. Describe the weather station you constructed. ______2. Did you complete the weather observation chart for three months?______3. List the experiments you completed. ______4. Indicate talks and demonstrations you gave for your weather project. Title Audience No. of People Date Award/Recognition ______5. Indicate the leadership/citizenship activities you completed as part of this weather project. Type of Activity Where Number of People Date ______6. Did you submit weather records for county competition? ______Award or recognition: ______

7. On a separate sheet of paper, write about the things you have learned and done in this project. Include three to five photographs of you working on your project.

18 U. S. C. 707 ______Member’s Signature Leader’s Signature

Educational programs of the Kentucky Cooperative Extension Service serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director of Cooperative Extension Service, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright © 2002 for materials developed by the University of Kentucky Cooperative Extension Service. This publication may be reproduced in portions or its entirety for educational or nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at: http://www.ca.uky.edu. Issued 12-1985, Last printed 3-2002, 500 copies, 21500 copies to date.