Signal 1: Urban Heat Islands
Summertime in many urban areas can get hotter and hotter compared to their rural surroundings, thus forming what we call urban heat islands. These urban heat islands are caused by the development of urban infrastructure and its changes in radiative and thermal properties. There are two main heat island types: surface and atmospheric heat islands.
Surface urban heat islands forms due to the sun, heating on exposed urban surfaces such as roofs and pavement, making the temperatures hotter than the air. They are typically present at all times of the day and night, but most intense during the day in the summer.
Atmospheric urban heat islands are the warmer air, specifically in the layer of air between the ground and the tops of trees and roofs, in urban areas compared to the cooler air in nearby rural surroundings. They may be weak or non-existent during the day, but most intense at night or predawn and in the winter.
Many factors contribute in causing urban heat islands, but how do urban heat islands generally form?
- Reduced vegetation in urban regions; which in turns reduces the natural cooling effect of evapotranspiration
- Properties of urban materials; which contributes to the absorption of solar energy and causes the air above them to be warmer than the air temperatures in rural neighbourhoods.
- Urban Geometry; the dimensions and spacing of buildings within a city can influence wind flow, energy absorption, and a given surface’s ability to bounce back the radiation to space.
The study to reduce urban heat islands has recently caught community interest and concern, due to the increasing temperatures to the extreme in urban cities. There have been many strategies and attempts to solve this problem and it differs throughout the many urban cities across the world.
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Signal inspired from Reducing Urban Heat Islands: Compendium of Strategies
