Urban Heat Island: What Are Urban Heat Island?

What are urban heat islands?
Urban heat is a term used to describe an occurrence where built up areas are hotter than the rural areas they are in proximity to. As urban areas become more and more developed, changes occur in the landscape. Infrastructure replaces open land and vegetation. Surfaces where heat used to be absorbed are replaced by surfaces that are dry and don’t absorb heat. Changes like theses cause urban regions to become warmer than rural regions, this forms, in a sense, an “island” of hot temperatures in the landscape. The heat is created by energy from the daily activities of people in big cities. These activities include commuting (cars, buses, and trains), and recreational activities.

Causes of urban heat
Urban heat islands can manifest in various ways and in difference areas of a city with different scales. The intensity of urban heat islands depends on the building patterns, the buildings surface properties, and the amount of green space and trees in the city.
The geometry of the city plays a

They are indicators of how the suns energy is absorbed, reflected and emitted. Different materials react differently to incoming solar radiation. In the case of reflecting , solar energy reflectance is correlated to a materials colour. The darker the material the lower the solar reflectance and the opposite is true for light colours. Substances with low solar reflectance reflect very little incoming radiation such that most of the energy is absorbed by the object. Thermal emissivity is also an important property that contributes to urban heat. Thermal emissivity refers to a materials ability to emit or release thermal energy which it has absorbed. Materials with low emissive ratios will stay cool (heat is dissipated easily). Most Buildings are made of materials with high thermal emissivity so they absorb more heat than they give