Have you ever noticed that the temperatures in downtown Birmingham can be a lot different than the temperatures outside of downtown? This is because of an urban heat island. An urban heat island is a metropolitan area that is significantly warmer than the surrounding areas. This morning, for example, downtown Birmingham was at 75 degrees, while fifteen miles away in Trussville, the temperature sat at around 59 degrees. What causes it? During the day, buildings and roadways absorb a lot of heat. This is because the materials used, such as concrete, asphalt, and steel, have a different heat capacity and a lower albedo (the ability for a surface to reflect or absorb heat) than a rural area. Everyone has experienced getting in a warm car on a hot summer day. Maybe you’ve noticed that black cars tend to get hotter than white cars. That’s a result of albedo. Light colors reflect heat and dark colors absorb it. Things such as asphalt store more heat during the day which causes cities to become hotter faster and stay hot longer. It is in question whether urban heat islands have an effect on global warming. The number of cities continues to increase as more and more people are moving out of the countryside. So with more people comes more cities, and with more cities comes more heat. There really is nothing that can be done to fix urban heat islands, although some cities are now using lighter colored materials, which will reflect more heat and keep temperatures cooler than they would be if dark colored materials were used. So don’t be surprised if you live in Mountain Brook, Tarrant, Vestavia, cities right outside of Birmingham, if temperatures at your house are significantly different than those being reported on the weather for Birmingham. It’s all a result of the phenomena known as urban heat islands.
-Stephanie Frost, ABC 33/40 Weather Intern
