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When this photo was taken, the dark pavement on this stretch of Interstate 10 in West Texas was 11 degrees F warmer than the light pavement. Click image to enlarge.

The Citizen Scientist will occasionally issue a Citizen Science Challenge to members of the Society for Amateur Scientists, students and all other persons who might enjoy investigating an important science problem or question.

The Citizen Scientist and its archives have provided plenty of tips, ideas and instructions on how to do science. Amateur scientists spend much of their spare time actively pursuing serious science activities, projects, experiments and research. Citizen Scientist Challenges are aimed at these dedicated amateur scientists and for individuals, teams and groups of science enthusiasts who would like to join them by becoming serious amateur scientists.

The objective of each Citizen Science Challenge is to solicit solutions to a real problem. Portions or all of the best solutions will be published in The Citizen Scientist. Challenges can be investigated by individuals, teams or groups. There is no age limit. There are no academic qualifications. Whether you hold only a high school diploma or an advanced university degree, you are welcome to participate.

It is well known that cities are warmer than adjacent rural areas.This is known as the urban heat island effect. It is less well known that most artificial structures cause highly localized warming.

My daughter Sarah conducted a science project on this theme several years ago. During a vacation trip from Texas to New Mexico, Sarah attached a temperature data logger to her window of our car. The logger was installed inside a white tube to shield the sensor from direct sunlight. For details, see www.iscienceproject.com/success/5647_ss1-sarahmims.html.

We already knew that Sarah would find increases in temperature as we drove through towns and cities. We had measured that many times while driving across town to her school. However, I had no idea that she would also see small temperature increases as we drove past very tiny communities and even rural gas stations and road intersections.

This new information suggested an experiment, so at a remote site in West Texas we diverted from the paved highway to a nearby gravel road. The temperature along the gravel road was around a degree Fahrenheit cooler than the paved highway.

During this vacation, we drove along an unusual section of Interstate 10 in West Texas in which the pavement in one lane was black and that of the adjacent lane was very light. We wondered how much hotter the black pavement was.

The answer arrived the next year when I acquired a handheld IR non-contact thermometer. During a subsequent trip on a hot summer day, we found that the black pavement was 10-15 degrees Fahrenheit warmer than the light pavement.

On 9 April 2004 I again drove this section of Interstate 10, this time during a field trip to capture smoke from Southeast Asia. As shown in the photographs below, at approximately 1430 hours Central Standard Time with a nearly clear sky, the temperature of the black pavement was 113 degrees F and that of the light pavement was 102 degrees F, a difference of 11 degrees F.

Temperature of dark asphalt. Click image to enlarge.

Temperature of light asphalt. Click image to enlarge.

The photos below show that the temperature of the gravel shoulder that borders the highway was typically 87 degrees F, and that nearby native shrubs were considerably cooler at only 67 degrees F.

Because of the phenomenon known as thermal lag, the temperature difference of the two shades of asphalt lasts well into the night. When I drove along the same highway the following morning, a cold front had arrived, and the sky was totally overcast. Yet the black pavement was still a few degrees warmer than the light pavement.

(Note: The IR thermometer was photographed when set to indicate temperature in both Celsius and Fahrenheit. The Fahrenheit photographs are shown here, because the Fahrenheit scale has higher resolution than the Celsius scale.)

What will be the effect on temperature during a sunny summer day and the following night (no clouds) if all roads and parking lots in your community, State or the United States paved with black asphalt are converted to a material with a higher albedo (reflectance)?

You can use data on the Web or from libraries to find the total miles (kilometers) of paved roads in your community, State or the U.S. Be sure to account for roads with multiple lanes. Finding data for private drives and parking lots may be more difficult.

Find out what temperature changes can be expected by using high alb edo pavement. Is gray concrete a better choice than white asphalt? Search the Web to find appropriate data.

For example, in “Islands of Warmth in a Sea of Cool”(Alaska Science Forum, Article No.1458, Geophysical Institute, University of Alaska Fairbanks, September 1999, www.gi.alaska.edu/ScienceForum/ASF14/1458.html), Ned Rozell reported on test results with black asphalt and an experimental white asphalt. Aged asphalt appears gray and absorbs around 90 percent of incident sunlight. White asphalt absorbs only 50 percent of incident sunlight. Tests with fresh black asphalt and faded asphalt gave temperatures of, respectively, 123 and 115 degrees. The experimental white asphalt reached only 90 degrees.

Are these results representative? Just as black asphalt gradually ages to a gray color, does white asphalt eventually become darker? Is gray concrete pavement more or less cost effective than white or gray asphalt.

Some satellites measure surface temperature. Can you use their data to estimate the heat island effect in your community? How much of the temperature increase is attributable to roads and parking lots?

Rather than modeling the problem mathematically, you may prefer to conduct experiments to measure the change. You may wish to measure the temperature of various shades of pavement.

Consider an experiment based on a physical model of your community in the form of a map of placed in a sealed box with a clear window and a thermometer. Place the box under a lamp for a fixed amount of time and measure the temperature change inside the box. Then remove the map and outline all the roads with black ink to simulate black asphalt. Be sure the width of the black ink line equals the width of the roads on the map. Repeat the light experiment to find the temperature change over the same length of time. Refine the experiment to be sure the reflectance of the unmarked and annotated map reasonably represent high and low albedo pavements.

The Citizen Scientist will publish the best solutions to the problem. Your answer can be as simple as a before and after temperature comparison for one day in your town or city. Or you can expand your study as much as you like. For your result to be seriously considered, you need to explain how you arrived at it. If you would like your result to be considered for publication in The Citizen Scientist, you need to submit an organized, well written report.

This question can be as challenging as you want to make it. So we look forward to seeing your results. While there is no time limit, it would be good to publish some results during the upcoming summer months.

Students, please let us know if you investigate this challenge as a science fair project. If your project is well done, please send us your findings and a photo of your science project display.