Weather Tidbits: Urban Heat Island Effect

This edition of Weather Tidbits will be discussing the urban heat island effect. The difference between temperatures in a grassy field and a city can be very different because of the different material on the ground. A grassy field with trees will likely be cooler than a city. There are numerous reasons for the added heat in a city and an urbanized environment. The asphalt and any dark rooftops retain heat easily, and concrete reduces surface moisture. The dark-colored surfaces overall retain heat more efficiently than lighter colored pavement, and the reduction of surface moisture prevents any evaporation. Evaporation is the process of converting liquid water into a gas, which can be done via heat from the sun. Since heat energy is used for evaporation, the surrounding environment will be cooler. But of course, reduced surface moisture prevents this. Heat can also emit from buildings, cars, and factories.

Rural and less urbanized areas have the benefit of being cooler. There are generally more trees in rural locations, which provide shade. Trees and plants can also cool down an environment via evapotranspiration. Evapotranspiration is the evaporation of moisture accumulated within the leaves of plants and trees through the ground and root system. Less blacktop and infrastructure keeps rural areas cooler as well. This can be the difference between 85 degrees in a rural area and 92 degrees in a city.