Breakdown: Urban Heat Island Effect, why it’s hotter in the city

Breakdown: Urban Heat Island, why it's hotter in the city

MEMPHIS, Tenn. (WMC) -You may have wondered when looking at the temperature map. Why is Memphis always warmer than the surrounding areas? The reason is referred to as an urban heat island. An urban heat island happens when cities experience much warmer temperatures than surrounding rural areas. This difference in temperature between urban or city and areas that are more rural, or in more of the country and not as developed, has to do with whats on the surfaces in each area.

The sun heats up and lights both city and more rural areas exactly the same. The difference in temperature between the two depends on how surfaces and materials hold in heat.

If you travel to a rural or country area, you’ll probably notice that it is mainly covered with greenery and farmland can extend as far as the eye can see.

Urban Heat Island
Urban Heat Island (Source: Wikimedia)

Plants take up water from the ground through their roots. The water is absorbed water the plants take in, is absorbed and stored in the leaves. The water moves into tiny holes on the underside of leaves. The liquid will then turn into water vapor and is released into the air. This process is known as transpiration and. is a way the atmosphere gets cooled.

In the city, it’s a different scene. It’s more sidewalks, people, streets, parking lots and tall buildings. These structures are typically made cement, asphalt, brick, glass, steel and dark roofs. These materials act to absorb heat. So the object itself is usually hot or warm to touch. Not to mention densely populated areas with people who release energy in the form of heat. Cars and buildings that are close together and tall. This heat as no where to escape. Nighttime temperatures can be the time when Urban Heat Islands are seen more clearly. This is because buildings, sidewalks, and parking lots can block heat coming from the ground from rising. The heat is trapped on lower levels which means warmer temperatures.

On the hand objects tend to reflect light. Temperatures of the lighter object do not increase as much. The buildings in cities are mostly made of dark objects like building materials which absorb heat.

Some cities can be as much as 7°F hotter than its surrounding areas. These hotter temperatures can cause people to become dehydrated or suffer from heat exhaustion.

To help bring down the temperature in these urban heat islands, some cities are making changes by using lighter materials and materials that can absorb water. Some areas are covering black asphalt streets, parking lots, and dark roofs with a more lighter and reflective gray coating. Some of these changes can reduce city air temperatures drastically. Some areas are planting gardens on rooftops.

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