Title: Precipitating Weather (Meteorology) Grade Level(s): 6-8 Introduction: There has probably been a small increase in global precipitation over land during the twentieth century. When speaking of precipitation, cloud droplets are dew which forms on tiny dust and salt crystals which are blown by the winds. These condensation particles are so minute that they can only be observed under the electron microscope with a magnification of several thousand times. The most efficient particles result from the evaporation of water from tiny droplets in the spray from the ocean. Precipitation has increased over land in high latitudes of the northern hemisphere in conjunction with temperature increases. Precipitation has decreased after the 1960 s between the equator and about 35 degrees latitude, from Africa to Indonesia, as temperatures increased. Learner Objectives: Students will be able to demonstrate the formation of clouds. Students will be able to differentiate between precipitation, evaporation and condensation. Students will be able to understand the phenomenon of global precipitation. Sunshine State Standards: Science: SC.H.1.3.5, SC.A.1.3.5; Math: MA.B.3.3.1, MA.B.4.3.1. Competency-Based Curriculum: Science : Sci.M/J1 I-3-A Math: M/J1 III-3-A, M/J3 II-13-C Materials: 1. 1 liter of water 2. Kettle 3. Glass bowl with ice 4. Pie tin 5. Water colors 6. A few sheets of shiny paper I-B-14
Activity Procedures: 1. Boil 1 liter of water in a pot ( to be used in the second section ). 2. Pass out two sheets of shiny paper, a cup of water and a set of water colors to each student. 3. Have the students dip their brushes into the yellow paint. 4. Have the students make many large yellow drops over one sheet of the shiny paper. 5. Rinse the brushes off and dip the brushes into the blue paint. 6. Make many blue drops between the yellow drops. Be sure that the students do not mix the colors. 7. With a second sheet of shiny paper covering the desk, have the students lift their paper so that it is perpendicular to the desk and the drops start to run down the paper. 8. The drops should slide down the paper and mix with each other dripping off the bottom of the paper as large green drops. 9. Ask students a series of questions such as: A. What happened to the blue and yellow drops when you lifted your paper? B. What happened to the paper flat on your desk? C. Is there a new color on your paper? D. If there is a new color what is that color? E. How did the new color get there? F. Were the drops which fell off the bottom of your paper the same size as the blue and yellow drops? 10. The class should gather around a common work place where they can view the hot pot of boiling water and the bowl of ice. 11. The teacher should hold the bowl of ice water over the pot of boiling water. I-B-15
Activity Procedures (Cont d): 12. Ask : What do you think will happen-to the bowl of ice? To the steam? To the bottom of the bowl? 13. Once the water is boiling, hold the bowl of ice over the steam. 14. Place a pie tin so that the water which drips from the bottom of the bowl will collect in the tin. 15. The class should observe and share what they observe happening. Some questions which should help are: A. What do you see happening on the bottom of the bowl? B. What do you see happening on the bottom of the pie tin? C. How does the water get on the bowl? D. Are the water drops on the side of the bowl the same size? Why? E. Which drops are falling from the bowl? Why? F. Which drops look like rain? G. Which drops look like a cloud? H. How are the big drops formed? 16. Explain that the small misty drops which have condensed onto the side of the bowl of ice represents a cloud.the winds in a cloud blow the small drops around so that they collide with one another. During these collisions, some drops will combine with others making larger and larger drops. When the drops become so large that the winds cannot keep them in the sky, the drops fall as precipitation. This is similar to the large drops falling from the bottom of the bowl. Vocabulary: global precipitation, condensation, evaporation Student Assessment: Allow the student to answer critical thinking skills questions assigned by the teacher: A. Identify ten common types of clouds and list which of these produce precipitation B. Stimulate student thought by asking the following questions: 1. What is rain? 2. How is rain made? 3. What are clouds made of? I-B-16
Activity Extensions: 1. Allow students to construct a Venn Diagram which compares and contrasts five different types of precipitation. (Language Arts) Home Learning Activity: Have students calculate the amount of rainfall in Miami for the hurricane season in inches and convert them into metrics (cm.). References/Related Links: http://www.ncdc.noaa.gov/ol/climate/globalwarming.html http://ww2010.atmos.uiuc.edu/(gh)/guides/mtr/cld/home.rxml ftp://www.gsfc.nasa.gov/pub/pao/releases/2001/01-05.htm I-B-17
Precipitating Weather Reading Passage Precipitation is any form of water (either liquid or solid) that falls from the atmosphere and reaches the ground, such as rain, snow, or hail. Changes in tropical precipitation patterns have noted a higher frequency of the El Niño phenomenon over the past twenty one years. When this event occurs, the world can expect more months with unusually high, or low, precipitation with droughts more common than floods over land areas. There has been a 1% increase of precipitation over land during the 20 th century. Snow is made up of transparent ice crystals formed around dust or other small particulates in the atmosphere when water vapor condenses at temperatures below the freezing point. Because of the infinite variability of weather conditions, every crystal is unique in its precise configuration, and it is the large number of reflecting surfaces of the crystal that makes snow appear white. Hail, another form of precipitation consisting of roughly spherical pellets of ice and snow, is usually combined in alternating layers. True hailstones occur only at the beginning of thunderstorms and never when the ground temperature is below freezing. Often several hailstones freeze together into a large, shapeless, heavy mass of ice and snow. Clouds are visible aggregates of tiny water droplets and/or ice crystals suspended in the atmosphere and can exist in a variety of shapes and sizes. Some clouds are accompanied by precipitation; rain, snow, hail, sleet, even freezing rain. I-B-18
Precipitating Weather FCAT Questions Directions: Read the passage, then answer the questions. Answer multiple choice questions by circling the letter of the answer that you select. Write your answer to the Read, Think, and Explain question on the lines provided. 1. Changes in precipitation over the tropical Pacific are related to: A. High latitudes B. Temperature increases C. El Nino D. Global warming Answer: C 2. Global precipitation over land during the 20 th Century has changed by what amount? A. 10% increase B. 10% decrease C. 1% decrease D. 1% increase Answer: D 3. Changes in precipitation are consistent with changes observed in: A. Lake levels B. Oceanic temperature C. River currents D. Cloud types Answer: D 4. Discuss the differences between precipitation, evaporation, and condensation. I-B-19