DISCUSSION: In cities, asphalt and concrete surfaces are especially effective at absorbing and trapping heat. In addition, all the cars, planes, and industrial processes increase the amount of heat in cities. Thus, cities trap all this heat during the day and hold onto it at night such that nighttime temperatures in cities can be 10-20 degrees warmer than the surrounding rural areas. This is the urban heat island effect. Heat exhaustion and heat stroke are typically brought on by extended exposure to the heat. Thus, heat-related illnesses are especially a problem in cities that don't cool off much at night increasing the continuous length of time people may be exposed to the heat. In rural areas, people can get some relief and recovery from hot days during the night. The urban island is an issue in cities across the globe, but is especially a problem in Phoenix, AZ which resides in the middle of the desert. The picture above shows "heat ripples blurring the downtown (Phoenix) skyline" as a plane lands. Five people have already died this year in Maricopa County, AZ (Phoenix resides in this county) due to heat related illnesses and another 34 cases are being investigated.
Given the danger of the urban heat island effect, it is important to find ways to limit the effect. One of the least expensive ways is to plant trees in the city. Trees provide shade and use some solar radiation for evaporating water from their leaves that would otherwise be used to heat the surrounding landscape. Phoenix officials have agreed to plant 3000 trees this year, and numerous other cities have embarked on plans to plant more vegetation in their cities. Another option for reducing the heat island effect is to use lighter colored asphalt and roofing materials that will reflect more solar radiation rather than absorb it. Using different building materials is likely a more expensive option than planting trees, but a combination of approaches is likely necessary in order to observe a significant reduction of the urban heat island effect. The main takeaway message here is that the urban heat island effect is a serious public health issue, but there are options for reducing this effect. Many cities are beginning to understand the seriousness of this issue and take steps to fight the effect.
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© 2018 Meteorologist Dr. Ken Leppert II