Weather Making Cities – Wetter Cities

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Spend any time in a city during the summer and you’ll find that urban areas are much warmer than the surrounding countryside. The reason is what’s known as the “urban heat island effect,” and it effects more than just the temperature. I’m Jim Metzner and this is Pulse of the Planet.

“From our studies what we’re seeing is that, at least, in fairly large urban areas, such as Atlanta or perhaps New York City – because of the influence of the city on heating up the air that kind of presides over the city itself – that it can in fact cause cities to be, wetter than rural areas.”

Dale Quotrocci is a senior scientist at the Marshall Space Flight Center. Researchers there are using NASA technology like remote sensing to learn about how cities may actually create their own unique weather patterns. It happens because during periods of hot weather, cities actually trap the heat.

“Sunlight on very warm days is focused on a city or an urban area, the buildings and pavements and concretes, absorb sunlight and keep absorbing it throughout the daytime, and store it. Then two to three hours, or so, after sunset, they release this energy back into the lower atmosphere and it heats up the area above the city to the point where there is a two to five, even higher Fahrenheit degree difference over the city, as opposed to rural areas. Cities actually create this dome of elevated air temperature over them called the urban heat island effect.”

That dome of heated air creates a low pressure system over the city, drawing in cooler and moister air from surrounding areas. When this cool air is exposed to hot city streets and buildings, it warms, rises, and forms clouds, which are likely to drop more rain on the city itself.

Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.

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Weather Making Cities - Wetter Cities

The cityscape is an environment that creates a micro-climate unto itself.
Air Date:02/02/2006
Scientist:
Transcript:

music

ambience: traffic

Spend any time in a city during the summer and you'll find that urban areas are much warmer than the surrounding countryside. The reason is what's known as the "urban heat island effect," and it effects more than just the temperature. I'm Jim Metzner and this is Pulse of the Planet.

"From our studies what we're seeing is that, at least, in fairly large urban areas, such as Atlanta or perhaps New York City - because of the influence of the city on heating up the air that kind of presides over the city itself - that it can in fact cause cities to be, wetter than rural areas."

Dale Quotrocci is a senior scientist at the Marshall Space Flight Center. Researchers there are using NASA technology like remote sensing to learn about how cities may actually create their own unique weather patterns. It happens because during periods of hot weather, cities actually trap the heat.

"Sunlight on very warm days is focused on a city or an urban area, the buildings and pavements and concretes, absorb sunlight and keep absorbing it throughout the daytime, and store it. Then two to three hours, or so, after sunset, they release this energy back into the lower atmosphere and it heats up the area above the city to the point where there is a two to five, even higher Fahrenheit degree difference over the city, as opposed to rural areas. Cities actually create this dome of elevated air temperature over them called the urban heat island effect."

That dome of heated air creates a low pressure system over the city, drawing in cooler and moister air from surrounding areas. When this cool air is exposed to hot city streets and buildings, it warms, rises, and forms clouds, which are likely to drop more rain on the city itself.

Pulse of the Planet is presented by the National Science Foundation. I'm Jim Metzner.

music