Here's how cities make the environment hotter
Sunday, August 25, 2013, 9:04 -
North American summers can be as sweltering as any and if you happen to be in a major city, they can be even hotter.
Graphic artist Nickolay Lamm, in a blog post for StorageFront.com that shows New York cityscapes and famous landmarks through the lense of a thermal imaging camera, says the abundance of buildings and asphalt with dark surface absorb and release heat. That, combined with the relative lack of vegetation, which aids in evaporation and cooling, can raise the average temperature of cities and other urban areas by up to 10 degrees Fahrenheit (around 6 degrees Celsius).
Lamm says he was inspired to create the project after walking around Manhattan in 36C heat earlier this summer.
"In the U.S., heat kills more people than floods, hurricanes, lightning and tornadoes combined," Lamm writes. "The added heat in urban areas causes significant property damage. With 35 per cent (and rising) of self storage facilities located in cities, you may want to take extra precautions when storing delicate items."
Lamm teamed up with University of Chicago professor John E. Frederick to explain the science behind the thermal images. Below is a selection of shots, with Dr. Frederick's supplied explanation in parentheses.
"The white strips of the crosswalk reflect sunlight and are therefore cooler (yellow, orange) than the street’s dark surface (red). Contact with the air below street level apparently keeps the sewer grate relatively cool (green). Dark surfaces contribute to the urban heat island effect, while white surfaces have the opposite effect."
Statue of Liberty
"The water remains relatively cool (blue) all day while the Statue of Liberty warms up when exposed to the sun (red). A haze layer exits near the ground, and the particles and droplets in this layer emit “longwave thermal radiation” in the far infrared portion of the spectrum. The haze closest to the ground is relatively warm (red, orange), while the temperature decreases with increasing altitude (yellow to green to blue). The ground is heated both by sunlight and the longwave radiation emitted by the atmosphere. Haze layers over urban areas increase the longwave heating, especially overnight, and promote warmer temperatures."
"Human metabolism releases heat. People emit more thermal radiation (red) than their relatively cool surroundings (mainly green). Electric screens emit heat and appear red, while shaded areas are blue. The combination of energy use and high population density acts to increase the air temperature in a large, concentrated urban area, although the overall effect of human metabolism is small compared to other sources of urban heating."
Grand Central Station
"Human metabolism releases heat. People in Grand Central Station therefore emit more thermal radiation (green, yellow) than their relatively cool surroundings (blue). Note that the windows are almost invisible in the thermal image, indicating little temperature contrast between the interior and exterior. In principle, a high population density acts to increase air temperature in a large, concentrated urban area, although this is a very small factor compared to other effects associated with the structure of a city."
"The windows of the building in the center are cooler (dark green) than the solid materials in the surrounding wall (yellow, light green). This likely arises from indoor air conditioning and the fact that windows provide a weaker barrier to energy flow than do thick walls. Regions that experience direct solar illumination are relatively warm (red). The vertical walls provide added area for absorption of solar radiation and increase the urban heat island effect in their immediate vicinity."
"The lower electric screen generates heat and appears red in the thermal image. The upper screen generates less heat (yellow, red). Walls that do not receive direct sunlight remain relatively cool (blue). The release of heat via concentrated energy use contributes to the air in urban areas being warmer than in rural surroundings."
You can find more of these thermal images on Lamm's original post.