Albedo is “the fraction of the total solar radiation incident on a body that is reflected by it. ” Surfaces that have high albedo values absorb less incident radiation. Albedo is “the fraction of the total solar radiation incident on a body that is reflected by it. ” Surfaces that have high albedo values absorb less incident radiation. Albedo values of some materials found in the urban areas are shown in Figure. Even if two surfaces have a similar albedo, the incident energy does not always result in similar temperatures because the thermal capacity of those surfaces may differ.
Concrete, which is used as construction material extensively all around the world, has many benefits. Concrete has an albedo value ranging from 0. 1 to 0. 35. These values are higher than those of some other materials, and it is also lighter in colour. Factors that cause a higher temperature in urban areas: – more buildings running furnaces or air conditioners which emit heat – more areas paved with dark-coloured asphalt – more dark-coloured flat roofs – denser traffic with internal combustion engines – less reflective snow cover in winter time Other causes of a UHI are due to geometric effects.
The tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated. This is called the “urban canyon effect”. Another effect of buildings is the blocking of wind, which also inhibits cooling by convection. Waste heat from automobiles, air conditioning, industry, and other sources also contributes to the UHI. High levels of pollution in urban areas can also increase the UHI, as many forms of pollution change the radiative properties of the atmosphere.