WEATHER PREDICTION 



43 



How are clouds used in forecasting weather? 



e. Problem 5 



What is relative humidity? 



How is relative humidity measured? 



f. Problem 6 



How are weather maps made up? 



Study the weather maps in Figure 66 and find out 



what each kind of marking on them means. 

 In what general direction do storms move across the 



United States? 

 What is an isobar? 

 What is an isotherm? 

 For what is the weather map used by industries? By 



farmers? By fruit growers? By shippers? 

 From the weather maps in Figure 66 determine the 



type of weather in your locality on each of the days 



represented. 



2. You may find the following new words and 

 phrases in this study: 



centigrade a temperature scale made on the basis of 



100 degrees ; on this scale water freezes at and 



boils at 100. 

 Fahrenheit a temperature scale on which the freezing 



point of water is 32 degrees and its boiling point 212 



degrees. 

 isobar a line on a weather map drawn through points 



of the same barometric pressure. 

 isotherm a line on a weather map drawn through 



points of the same temperature. 



3. In the study of this topic the daily weather map 

 should come to your school. Apply to the nearest city 

 where it is printed and state for how long a period 

 you would like it sent. 



4. Make a class book of weather lore and try to 

 find a scientific principle upon which each saying 

 might be based. Ask your instructor. 



5. Read the barometer, watch the cloud forms and 

 the shifting of the winds, and try to forecast the 



weather for yourself. This will 

 prove very interesting and 

 worth while. 



EXPERIMENTS OR DEMON- 

 STRATIONS WHICH WILL 

 HELP ANSWER THE PROB- 

 LEM QUESTIONS 



Experiment 29. How does the 

 air thermometer work? 



Fit a one-hole stopper to a small 

 flask and insert a piece of glass tub- 

 ing about eighteen inches long. 

 Place the lower end of the glass 

 tubing under the surface of some 

 colored water in a beaker. With a 

 Bunsen burner heat the flask gently 

 until several bubbles of air have 

 escaped. Allow the flask to cool to 



nc. 71 



room temperature and mark the position of the liquid in 

 the tube. Mount the flask and tube on a ring stand and, on a 

 paper scale fastened behind the liquid column, mark the 

 different levels of the liquid at different room temperatures. 



An electric light bulb which has had the brass shell re- 

 moved and the stem filed out may be used as a flask. 



Summarize your observations and what you have learned 

 in a clear statement in your notebook. 1 



Experiment 30. How does the liquid thermometer 

 work? 



Use a small flask or an old electric light globe for a 

 thermometer bulb and place a one-hole 

 rubber stopper in its top. Through the 

 one-hole stopper place a two-foot length 

 of glass tubing of small bore. Fill the 

 bulb with water which has been colored 

 with ink. The bulb should be filled to 

 such a point that when the stopper and 

 tube are replaced the water will rise sev- 

 eral inches in the tube. Support the 

 water thermometer on a tripod or ring 

 stand and heat the bulb gently. Observe 

 the water level in the tube closely and 

 record your observations below. After 

 heating has continued for some time al- 

 low the water to cool to room tempera- 

 ture. After comparing with a mercury 

 thermometer mark this point on a scale 

 fastened behind the tube. 



In your notebook 2 record the notes 

 of this experiment and complete the 

 following statements. 



When the flask was first heated the 

 water level in the tube . After- 

 ward it began to When the water 



is it (expands, contracts) and 



rises in the tube. When the temperature 



falls the water and the level in the 



tube again 



Experiment 31. How are weather maps read? 



Carefully study the three weather maps in Figure 66. 

 Note the solid lines and the broken lines in all three of the 

 diagrams. Learn how the temperature of a given place is 

 indicated and what an isotherm is. Learn how the baro- 

 metric pressure of a given point is told, what isobars are, 

 and how they are drawn. How are weather conditions of a 

 certain locality on the map indicated? How is wind direc- 

 tion marked? Study the weather conditions as indicated 

 in several low-pressure areas. What is the pressure at the 

 center? How does the pressure change as you go away 

 from the low ? What is the general wind direction about the 

 low-pressure area ? Study the weather conditions as in- 

 dicated in several high-pressure areas and answer the same 

 questions as before. 



In your notebook 3 carefully summarize what you have 

 learned from this investigation, giving information on each 

 of the questions suggested in the directions above. 



Experiment 32. How do cyclonic and anticyclonic 

 areas travel across the country? 

 Locate a low-pressure area in the western part of the 



1 See workbook, p. 18. 

 1 See workbook, p. 19. 

 ' See workbook, p. 19. 



FIG. 72 



