The urban climate, and with it the well-known urban heat island (UHI) phenomenon, has to be seen as a negative factor for thermal comfort and air pollution. 14 The UHI refers to the phenomenon where the temperature in an urban environment is always higher than that in surrounding rural areas, especially on calm and cloudless nights.
Density and urban sustainability
Land surface cover
Land surface cover is the foremost contributor to urban heat. Changes in land cover, such as deforestation and urbanisation, significantly influence regional- and local-scale urban climate due to the energy balance factors.
the spatial contiguity of urban development makes a statistically significant contribution to the UHI effect.
However, urbanisation has differing effects on heatwave occurrence and urban heat in relation to density. The rate of increase in heatwaves is ‘higher in sprawling than in more compact metropolitan regions’. This association is ‘independent of climate zone, metropolitan population size, or the rate of metropolitan population growth’.
The impact of solar radiation depends, in part, on the height of buildings and spacing between them, the height-to-width ratio. Radiant heat loss to the sky from the ground level is also affected by the ‘sky view factor’, the urban hemisphere height-to-distance ratio . Restricted sky views in dense urban higher rising centres is an indicator of reduced radiant heat loss to the sky from the ground level.
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Urban Development Policies Study notes for M. plan Sem-II
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