Heat islands
Introduction
Urban heat islands (UHIs) are metropolitan areas that are significantly warmer than their surrounding rural areas due to human activities. The term "heat island" describes built up areas that are hotter than nearby rural areas. The UHI effect is most noticeable during the summer or dry season.
Formation
Heat islands form as cities replace natural land cover with pavement, buildings, and other infrastructure. These surfaces absorb - rather than reflect - the sun's heat, causing surface temperatures and overall ambient temperatures to rise. The lack of vegetation also means that less cooling through photosynthesis is taking place.
Factors Contributing to Heat Islands
Several factors contribute to the UHI effect. These include city size, weather conditions, geography, and the amount and type of vegetation in the area. Larger cities tend to have larger heat islands. Weather conditions can also play a role, with clear skies and calm winds increasing the UHI effect.
Impacts of Heat Islands
Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution levels, and heat-related illness and mortality. Other impacts include reduced water quality.
Mitigation Strategies
There are several strategies to mitigate the UHI effect. These include increasing tree and vegetative cover, installing green roofs, and using cool pavements. All of these strategies help to cool the city by reflecting more sunlight and absorbing less heat.