The school wants to find a way to cool down their parking lot playground while still keeping some parking spaces for special events in the evenings.
Some days it is even too hot to play any games comfortably. But it gets very hot on the blacktop, especially at the start and end of the school year when outdoor temperatures are high. Imagine a school that, due to limited space, has to hold recess out in the parking lot. Would it feel different to be in an undeveloped area during that same time? Why?.What do you think it would feel like to be in a developed area during a hot summer’s day?.What is the relationship between the developed land and the brightness temperature?.Satellite-produced maps of Providence, Rhode Island highlight the role that differences in development patterns and vegetation cover can have on the magnitude of a city’s urban heat island. Examine these two images of Providence, Rhode Island. For purposes of this activity, think about brightness temperature as a proxy for surface temperature, similar to what you measured in the first part of this activity.
Researchers at NASA Goddard study the urban heat island effect using satellite maps that show visible light, land development, vegetation cover, and a quality called brightness temperature. In developed areas with lots of buildings and people, the effect of albedo can contribute to a phenomenon known as an urban heat island, which is a region whose average temperature is higher than surrounding rural areas. How do you think the effect of albedo could impact a city? If a dark section of pavement absorbs more of the sun’s energy than it reflects, then that section will feel warmer over the course of a sunny day. For more on other phenomena at play, see this video and article from NASA. It’s important to note, though, that a surface’s albedo isn’t the only property that affects how warm or cool a surface becomes upon exposure to sunlight. The albedo of each surface played a role in how much the temperature changed between your first and final measurements. In the previous activity, you measured the temperature of several types of surfaces around your school.
That’s why an asphalt parking lot will feel hot if you walk across it on a sunny day. When a material absorbs solar radiation, some of that light energy is converted into heat energy, and the material warms up. Why do darker materials feel hotter than lighter ones when both are exposed to sunlight for a period of time? In general, lighter-colored materials reflect more sunlight than darker colors and therefore have a higher albedo. Fresh asphalt, Flickrįresh asphalt, for example, has an albedo of around 0.05, which means that only 5 percent of the light is reflected. In other words, a 1 on the albedo scale means 100 percent reflection. A 1 means that a material reflects all of the light energy that hits it. A 0 means that the surface of a material absorbs all of the sunlight that hits it.
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