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A definition of urban heat island is: "The relative warmth of a city compared with surrounding rural areas." [14]: 2926 This relative warmth is caused by "heat trapping due to land use, the configuration and design of the built environment, including street layout and building size, the heat-absorbing properties of urban building materials, reduced ventilation, reduced greenery and water ...
Unequal threat of heat stress in urban environments is often correlated with differences in demographics, including racial and ethnic background, income, education level, and age. [1] While the general impacts of urban heat inequity depend on the city studied, negative effects typically act on historically marginalized communities. [ 1 ]
The urban environment has two atmosphere layers, besides the planetary boundary layer (PBL) outside and extending well above the city: (1) The urban boundary layer is due to the spatially integrated heat and moisture exchanges between the city and its overlying air. (2) The surface of the city corresponds to the level of the urban canopy layer.
The urban heat island is a phenomenon in which central regions of urban centers exhibit higher mean temperatures than surrounding urban areas. [38] Much of this effect can be attributed to low city albedo , the reflecting power of a surface, and the increased surface area of buildings to absorb solar radiation. [ 21 ]
An urban thermal plume describes rising air in the lower altitudes of the Earth's atmosphere caused by urban areas being warmer than surrounding areas. Over the past thirty years there has been increasing interest in what have been called urban heat islands (UHI), [1] but it is only since 2007 that thought has been given to the rising columns of warm air, or ‘thermal plumes’ that they produce.
The worst heat wave in Australia occurred in 1938–39 and killed 438. The second worst was in 1896. Power outages can also occur within areas experiencing heat waves due to the increased demand for electricity (i.e. air conditioning use). [15] The urban heat island effect can increase temperatures, particularly overnight. [16]
Increased urban land use and occupation alters the local thermal field resulting in the development of warmer regions known as urban heat islands (UHIs). [8] An urban heat island is a phenomenon where these surface temperature deviations and air in the lowest levels of the atmosphere are concentrated in urban areas and those immediately ...
An urban heat island occurs where the combination of heat-absorbing infrastructure such as dark asphalt parking lots and road pavement and expanses of black rooftops, coupled with sparse vegetation, raises air temperature by 1 to 3 °C (1.8 to 5.4 °F) higher than the temperature in the surrounding countryside. [76] [77]