Central Arizona-Phoenix Long-Term Ecological Research Project

Transcription

1 Title: Microclimates, Heat Islands & Shade Author: Ecology Explorers Education Team Time: 1 to 2 class periods Grade Level: 6-12 Central Arizona-Phoenix Long-Term Ecological Research Project Background: The contour of the land, materials of land cover, the presence or absence of plants, moisture and time of day may result in many climates (microclimates) within one ecosystem. The urban heat island is one way in which people affect the local climate in their urban ecosystem. Currently, during the summer, Phoenix experiences nighttime temperatures that are 12 o F warmer than the surrounding rural areas. The heat island occurs after sundown as large heat absorption during the day by cement, asphalt and other parts of the built environment is slowly released back to the atmosphere during the night. Scientists collect temperature data from weather stations across the Phoenix metropolitan area, but even within your schoolyard, your students can compare temperatures to test whether different materials or plants are making part of the schoolyard hotter or cooler. For example, shading and evapotranspiration (the process by which a plant actively moves and releases water vapor) from trees can reduce surrounding air temperatures as much as 9 F (5 C). Because cool air settles near the ground, air temperatures directly under trees can be as much as 25 F (14 C) cooler than air temperatures above nearby blacktop. ( Sep. 11, 2006). Why study microclimates? Temperature has an impact on the kinds of plants and animals that can live in a particular place Varying types of land cover can affect temperature The temperature can affect comfort levels of people, in turn affecting how much energy is used to keep people cool or warm. What kinds of scientific investigations can be developed from this activity? Students can compare data taken: on different ground covers (grass, sand, concrete, gravel, etc), at different times of the day, at different times of year at different types of shade (buildings, directly under a tree, shadow of a tree etc). This activity is divided into two parts. The first part suggests a procedure for creating a long-term data base of temperatures associated with various ground covers in your

2 schoolyard. The second part suggests possible research questions for students to investigate the affects of shade on various surfaces and around various objects (natural and man-made). The best condition for conducting these experiments is on sunny calm days. On windy days the air temperature may be uniform because the wind mixes the air. This lesson was written using the metric system, but you may decide to use feet and Farenheit measurements for temperature as these may be more meaningful for your students. Vocabulary: Urban Heat Island (UHI) effect a nighttime phenomenon where temperatures in urbanized areas are higher than in the surrounding rural areas. Minimum temperatures in metropolitan Phoenix's urban areas are about 12 o Fahrenheit (~6 o C) more than those in the outlying rural areas. Microclimate- local conditions of air and soil temperature, humidity, and wind speed, vary due to local differences in topography, light absorption and reflection, and air pollution. Thermal Conductivity- the amount of time it takes to transfer heat through an object Thermometer- used to measure temperature. There are digital, mercury-filled, and spirit-filled thermometers. Easiest to read and use are the digital thermometers although they can be less accurate and cost more. Objective(s): The student will be able to compare the land cover, shade and temperatures, in different microclimates to begin to explain how this impacts both people and other organisms. The students will be able to record temperature readings and detailed observations while exploring microclimates. Standards: Only looking at grades 5-12 Arizona State Science standards The standards listed are those the activity meets without doing any extensions or the activity as part of a larger unit. Many more standards can be met with the extension suggestions. S1-C1-GR5-8-Observations, Questions, and Hypotheses: Formulate predictions, questions, or hypotheses based on observations. Locate appropriate resources. S1-C2-GR5-8-Scientific Testing (Investigating and Modeling): Design and conduct controlled investigations. S1-C3-GR5-8 Analysis and Conclusions: Analyze and interpret data to explain correlations and results; formulate new questions S1-C4-GR5-8 Communication: Communicate results of investigations S1-C1-GRHS- Observations, Questions, and Hypotheses: Formulate predictions, questions, or hypotheses based on observations. Evaluate appropriate resources S1-C2-GRHS- Scientific Testing (Investigating and Modeling): Design and conduct controlled investigations. 2

3 S1-C3-GRHS-Analysis, Conclusions, and Refinements: Evaluate experimental design, analyze data to explain results and to propose further investigations. S1-C4-GRHS-Communication: Communicate results of investigations. S3-C1-GR5-PO2 Propose a solution, resource or product that addresses a specific human, animal, or habitat need. S3-C1-GRHS-PO4 Evaluate the following factors that affect the quality fo the environment: urban development Materials: Thermometer (one per plot) **Teacher note about thermometers: Calibrate the thermometers. Place all the thermometers into a beaker of ice water for 5 minutes. The thermometers should read between 0 o C to 0.5 o C. Choose one thermometer that is correct and label it the thermometer of excellence (TOE). Make a note of how each thermometer differs from the TOE and record on you data sheet. When you compare your data you will need to add or subtract this amount from your thermometer readings. Scale map of schoolyard (If available) or go to (or other mapping website) to get an aerial photo of the area Data Recording Sheets A Shady Situation from Chain Reaction 4: Urban Ecology, the article and PDF file can be found at Experimental Design Data Sheet Safety Precautions Make sure where you are gathering data is in a safe environment (i.e. you do not have to worry about cars running over you or trees falling on you.) Thermometers should be mercury free. They are cheaper and safer if they accidentally break. Suggested Procedure: 1. Discuss with your students that they are going to explore microclimates in their schoolyard. You might ask what they think a microclimate is and why they think it matters to them. Have the student read a Shady Situation in ASU s Chain Reaction 4: Urban Ecology. Have they noticed which parking lots have trees? What are some microclimates the students may have encountered traveling to school or in the schoolyard (i.e. pavement, grass)? 3

4 2. Define the boundaries of your study area. Have the students look at a scale drawing or aerial photograph of their schoolyard (or take them out to the study area). Have the students predict which surfaces will be hottest and coolest. Record their predictions. For older students, you may which to have several different study areas. 3. As a class decide on three to five different ground cover (grass, concrete, soil, sand, gravel, etc) points to compare. Make sure to record these locations on your map. If you don t have a scale map or aerial photograph, have the students draw a rough sketch of the area and record the location of these points. (teacher note: you may wish to have the students view the short video clip man-made materials and the heat island at ) 4. Select one point for your standard schoolyard air measurement. This point should be at least 2 meters (6.5 ft) away from a building and over gravel. If you don t have gravel you can use grass, dirt or concrete and make sure to note this on your data sheet). The standard temperature measurement should be taken at a height of 1.35meters (4.4 ft) with an aluminum foil skirt around the thermometer bulb to shade it from the sun. 5. Have the students take temperature measurements at each of the different ground covers and at the standard temperature site. Student should lay their thermometers directly on the surfaces (grass, concrete, etc.). Make sure the student taking the schoolyard standard measurement does not touch the bulb with his/her fingers. Have the students record the temperatures after 5 minutes. Record these temperatures on the class data sheet. 6. On the data sheet record the difference between each of the data points and the standard (groundcover standard). This number will give you how much higher ( a positive number) or lower (a negative number) the ground cover is in relation to the average temperature (the standard measurement) for your schoolyard. 7. Have your students record the official Phoenix (or your city s) temperature taken at approximately the same time (this is available from any weather website). You may have to convert this to o C. 8. Have the students complete the questions on the worksheet. 9. Continue to collect data from these same locations throughout the day or the year to see daily or seasonal changes temperatures. 10. Shade Comparison. In A Shady Situation, the scientist measured the surface temperatures around each tree at several distances from the trunk. She recorded the different surfaces at each of these distances. She also measured in each direction (N, S, E. & W) Based on your earlier measurements, what differences would there be among surface temperatures of different ground cover areas shaded by a tree? Do the surface temperatures change as you move from directly beneath a tree to the end of the tree s shadow? Is there a temperature difference between shade from a 4

5 building (blue shade) or from a tree (green shade) on the same type of surface? Have your students develop testable hypotheses about these or other shady questions and design experiments to test their predictions. What patterns did they find? If they were to design their schoolyard would they add more trees or more shade structures? Why or why not? Evaluation: Student completes data sheet with detailed observations and accurate temperature readings. Students complete the questions on the student handout. These answers should reflect some understanding that the landscape around the thermometer will affect the temperature it records and that some surfaces retain more heat than others. Students should design and conduct a study of shade and temperature. Extensions: Students can o Go back and visit plots to look for changes in plants and animals (or signs of animals) o Test for humidity, wind speed, measure canopy cover,. Have students take multiple temperatures in their study area and create a thermal map with isotherms ( Thermal Activity adapted from Cold n Hot activity (VanCleave, p. 126). o Students should be able to familiarize themselves with basic thermal principles. Before beginning the lesson have samples of different types of materials, plastic, different types of materials (plastic, concrete, rubber ). Place the different types of materials under the light source at the same time. Check the temperature of the objects and record. Use the next thirty minutes to begin the activity to talk about microclimates. After ten minutes, come back to the materials. You can use thermometers to check surface temperature or you could experiment with ice melting to see if there is a difference (the thermal conductivity will affect the melting rate). o o After approximately thirty minutes students will then check the temperature of the different objects. Record the temperature. Now take the objects out of the light for another thirty minutes. Record the temperature under shade at ten minutes intervals for thirty minutes. Did you notice any differences in heating amounts of ability to cool? Download a copy of outcomes (outdoor human thermal comfort export system). Let students plug in their data and change variables to see how they can change the surroundings to be more comfortable to humans (ie. change the materials around them, change the clothing they are wearing). 5

6 Resources Regional climate information Heat index Conversion heat index Heat Index Table Urban Heat island graphics of Phoenix Arizona Heat Island video (interview fo ASU scientist on newschannel 3) Akbari H, Davis S, Dorsano S, Huang J, Winnett S (1992). Cooling Our Communities: A Guidebook on Tree Planting and Light-Colored Surfacing. U.S. Environmental Protection Agency, Office of Policy Analysis, Climate Change Division. Lawrence Berkeley National Laboratory Report No. LBL Akbari H, Rosenfeld A, Taha H. (Feb.1990) Summer heat islands, urban trees, and white surfaces. Proceedings of American Society of Heating, Refrigeration, and Air Conditioning Engineers.10-14,. Atlanta, GA: American Society of Heating, Refrigeration, and Air Conditioning Engineers. Also published as Lawrence Berkeley National Laboratory Report LBL Höppe, P. (1999) The physiological equivalent temperature - a universal index for the biometeorological assessment of the thermal environment. International Journal Of Biometeorology 43 (2) p Oke, Thomas. (2004). Sitting and Exposure of Meterological Instruments at Urban Sites. 27th NATO/CCMS International Technical Meeting on Air Pollution Modelling and its Application, Banff, October, Patel, Tera (1995). Parisians Pale but Stay Warm. New Scientist 148 p. 10 VanCleave, Janice. (1991). Earth Science for Every Kid. John Wiley & Sons: New York 6

7 Climate Data Sheet: Groundcover in the Schoolyard If you use o F, please note this on the data sheet School: Date: Time: Official City Temp.( o C) Latitude/Longitude (if known) Standard Temperature ( o C): (taken at 1.35 m over gravel, at least 2 meters away from a building) Location of standard temperature measurement (please describe in detail so another person can find the same spot, also note if it is over something other than gravel) or mark it on a map: Study Site: please describe in detail so another person can find this study site You may not have all of the different types of ground cover at your school, test for those you do have and write NA (not applicable) for the others. Ground cover Temperature C at ground level Difference from Standard (Groundcover Standard) Grass Gravel Soil Sidewalk (concrete) Blacktop (asphalt) Sand Woodchips Mark the location of where each temperature measurement was taken on a map or sketch of the study site so you can continue to take measurements at the same location 7

8 Questions for Ground Cover Study: 1. Which ground cover did you predict would be the hottest? 2. Which ground cover did you predict would be coolest? 3. Which ground cover was hottest? 4. Which ground cover was coolest? 5. Give one possible explanation for why one ground cover is hotter than another. 6. Where would you like to stand if you were waiting for a bus? Why? 8

9 7. Is your standard schoolyard temperature higher or lower than the official Phoenix (or your city s) temperature? 8. How do you think the surface temperatures you recorded in your study area affect your standard schoolyard temperature? 9. How do you think the local surroundings affect the temperatures recorded by the official weather stations? 9

10 Rubric for Shade Investigation Students should complete a laboratory report after completing their shade investigation. The following is a possible rubric for a lab report consisting of: Heading, Introduction, Procedure, Results, and Conclusion for a total of 10 points. Heading- 1 pt. A few words describing what was done or found Introduction- 2 pts. Why is what you studied important? What was the question? Procedure- 2pts. How did you collect your data, description of the site (location, date, time, weather conditions?) Results-2 pts. What was found in the study, presence of at least one table or graph (with written explanation). Conclusion- 2 pts. Summary of what was found and the implications or why anyone should care what was found. Did the data answer your question? Ideas for further research. Mechanics- 1 pt. Grammar, spelling Major questions to consider in conclusion: What are some positive and negative aspects of humans on the environment (humans, plants, and animals), for the negative aspects what are some possible solutions? 10

11 Designing your Investigation Name(s) Question: Write your hypothesis and prediction: Write an alternative hypothesis and prediction: Method: Write down your method in detail so that someone who is not in your group could follow your method exactly the way you would. Use another sheet of paper to record and analyze the data and write your conclusions. 11

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