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Project Ideas continued
4. Measure the Heat Island Formed by a Road With an IR Thermometer.
All roads, from the simplest country lane to a modern Interstate Highway, are heat islands. The photograph below shows the heat island formed by Interstate Highway 10 west of Kerrville, Texas, at 1:09 PM on April 9, 2004. Note that the old, light tinted pavement is cooler (102 F) than the new, dark asphalt (113 F). The exposed gravel at the edge of the pavement is much cooler than either the light or dark asphalt. And the adjacent grass is much cooler than the pavement and gravel.
 Click to view enlarged version.
Photographs by Forrest M. Mims III.
Here's a graph of the temperature profile across the highway that assumes that the gravel and grass on both sides of the highway is at the same temperature:
 Click to view enlarged version.
This graph is based on the temperature of the grass, gravel and pavement. What is not shown is that the temperature of the air is also increased by the hot pavement. This results in a dome of warm air along the highway that blows where ever the wind takes it.
Project: Use an IR thermometer to make a temperature profile across a concrete sidewalk and both unpaved and paved driveways. Caution: Do not try this experiment on a real road! You could easily be struck by a fast moving car or truck!
Be sure to also measure the temperature of the gravel, soil or vegetation on both sides of the driveway.Make a graph of your measurements. If possible try this experiment on a sunny day and a cloudy day. If a camera is available, be sure to photograph the driveway and the adjacent soil, gravel and vegetation.
5. Measure Your Town or City's Urban Heat Island With a Conventional or Digital Thermometer.
The diagram below clearly shows an urban heat island, the dome of warm air over a city. The diagram also shows smaller heat islands over nearby suburban residential areas.
Environmental Protection Agency (EPA) diagram.
 Click to view enlarged version.
It's possible to make a heat island diagram of your neighborhood, town or city. Here is a heat island diagram of a small Texas city made from temperature measurements collected while driving a car across the city. The temperature was measured by means of a digital thermometer with a wire-connected temperature probe mounted outside the car in a white plastic tube that allowed air to flow past the probe while shielding it from sunlight.
 Click to view enlarged version.
The center of the town in the diagram above is at Court Street (the sixth red dot from the left), but the heat island is centered at the Holiday Inn, about 4 km north. This probably occurred because a south wind was blowing, which pushed the town's heat island northward toward the Interstate highway and the Holiday Inn.
Project: Use a conventional or digital thermometer to collect temperature measurements that you can use to make a heat island diagram of your neighborhood, town or city. The diagram above was made by using a department store digital thermometer with a outdoor probe connected to the readout by means of a thin, flexible cable. The probe was inserted inside a white plastic tube that was temporarily taped to the shady side of a car. While one person drove the car across the town, a second person wrote the miles (or kilometers) on the car's odometer and the temperature at various landmarks in a notebook. If you do not have access to a car, you can make temperature measurements every 50 or 100 paces as you walk across a neighborhood. Caution: Use great care when conducting this experiment. The driver must not be distracted by the experiment and must follow traffic safety regulations and common sense.
The graph above was made using a computer spreadsheet. You can also make the graphs using graph paper.
6. Find Heat Islands in Snow and Ice.
Where there is snow and ice during winter, heat islands can be observed without a thermometer. This is nicely demonstrated in the photos below made near Cloudcroft, New Mexico.
 Click to view enlarged version.
Photographs by Forrest M. Mims III.
Exposed wood is quickly warmed by sunlight. This is clearly shown in photo a above. (Living plants are warmed less than dead wood, but they are also warmed by sunlight.) Photo b above clearly shows the heat islands formed by young conifers. Rocks warmed by sunlight are also heat islands, as illustrated by photos c and d. Note the green leaves on the left side of the rock in photo d. It's quite possible that these leaves would not be green if they were not in close contact with the warm rock.
Project: If you live where there is snow during winter, make a set of photos that show both natural heat islands and those made or influenced by people. Compare the effect of sunlight on heat islands by placing identical dark-colored objects (dominoes, checkers, etc.) on snow in full sun and snow in the shade of a building or snow drift. Record what happens and, if possible, make photos of your artificial heat islands as sunlight warms one while the other remains in shade.
7. Reducing the Effect of Heat Islands.
If heat islands could be reduced or even eliminated, cities could be made cooler. Trees can greatly reduce the effect of heat islands. You can prove this for yourself by walking across a paved parking lot into the shade of nearby trees. You can learn how trees reduce the impact of urban heat islands at this site.
Heat islands made by people can be kept cooler by using construction, roofing and paving materials that are light colored. The photos below show the temperature (in degrees Fahrenheit) of exposed and painted asphalt in a parking lot on a hot summer day. The purpose of the white paint was to mark parking spaces, and the fact it was 9 degrees cooler than the unpainted asphalt did little to cool the area, since the parking lot was quite large. Nevertheless, these photos clearly show that heat islands can be cooled by using paving, building and coating materials that reflect sunlight.
 Click to view enlarged version.
Photographs by Forrest M. Mims III.
Project: Collect a variety of building materials (paint, shingles, wood, aluminum and so forth). Ideally the materials should be both unpainted and painted with a variety of colors. The samples do not need to be very large. Place the samples outdoors on a sunny day and measure their temperature after half an hour of exposure to full sun. Measure the temperature using a conventional, digital or infrared thermometer using these methods:
Conventional or Digital Thermometer: If the sample is heavy (brick, concrete, etc.), place the thermometer bulb or probe on top of the sample and cover it with white paper or aluminum foil. Wait a minute or so for the temperature to reach its maximum level and write the reading in your notebook or spreadsheet.
Important: Be sure that the maximum scale of the thermometer is not exceeded by the temperature of the sample. Cooking thermometers can be used to measure objects that become very hot in sunlight.
Infrared Thermometer: Place the sensor head of the thermometer close to the sample to make sure the temperature of the background doesn't influence the temperature reading.
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Questions:
1. True or false: Temperature is a measure of the energy in a substance.
2. An urban heat island is (a) a large highway sign that displays the outdoor temperature, (b) an island in a city pond of lake or (c) a dome of warm air over a town or city .
3. True or false: An infrared thermometer must touch the object whose temperature is being measured.
4. Which of the following materials is likely to become the hottest on a clear summer day: (a) mowed grass, (b) tall grass or (c) bare soil.
5. Is it possible for a satellite to measure the temperature of Earth from space?
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Going Further:
The links listed above provide much more information about temperature islands. By reviewing these links you will probably think of ideas for new projects. Urban heat islands are attracting more attention as cities become both larger and warmer. Science projects devoted to the reduction of urban heat islands using natural methods (like planting trees) or artificial methods (like using reflective building materials and paint) may provide important information for both individuals ands city planners. |
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Project Idea contributed by Forrest M. Mims III, Geronimo Creek Observatory, Texas
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