Taking a break from research papers to learn something new – Urban Heat Islands.
While a layman may think this sounds like a sweet spa to indulge in the cooler months (forgive the horrible joke), an urban heat island, or UHI, is an urban region that is significantly higher in temperature than its surrounding rural areas due to the uptick in human activities.
Right off the bat, I can identify an example from personal experience – Ross Park Mall, just outside the Pittsburgh city limits, shown below.
Another contributor to UHIs are energy usage and its consequent waste heat. As a population center grows, it tends to expand its area and increase its average temperature.
A symptom of this heat island effect is the discrepancy of rainfall in cities – monthly rainfall tends to be greater downwind of cities. UHI also decreases air and water quality by increasing the production of pollutants and allowing for the flow of warmer waters into ecosystems.
Mitigation of the urban heat island effect can be accomplished through the use of green roofs and the use of lighter-colored surfaces in urban areas, which reflect more sunlight and absorb less heat. While these seem like options mentioned in various sustainability performance measurements – such as LEED or P4 – the excessive wasted energy from urban areas could have disastrous consequences. In fact, concerns have been raised about the linkage of UHIs to global warming. While some studies did not detect a significant impact, other studies have concluded that heat islands can have measurable effects on climate phenomena at the global scale.
A literature review, titled “The Urban Heat Island Effect, Its Causes, And Mitigation, With Reference To The Thermal Properties Of Asphalt Concrete”, by students of the Royal Melbourne Institute of Technology, Australia, demonstrated that “UHI mitigation techniques are best used in combination with each other” (Mohajerani et al, 522). As a result of the study, it was concluded that the current mitigation measures need development to make them relevant to various climates and throughout the year, indicating the flexibility and adaptability that current sustainability performance measures may not have.
Some of the mitigation measures Mohajerani, Bakaric, and Jeffrey-Bailey mention range from designing “cool pavements” – paving materials that reflect more solar energy and enhance water evaporation to reduce heat island effect – increased utilisation of green spaces and green infrastructure within the urban landscape, and harnessing the cooling effects of wind and water.
The constantly expanding nature of cities and the increased use of heat absorbing substances evidently make a significant contribution to the heat island effect in urban areas. It would make sense that various mitigation measures described above should be used in combination with each other stands to be the most effective strategy for reducing the UHI effect.