Urban Climates and Heat Islands: Albedo, Evapotranspiration, and Anthropogenic Heat

Urban Climates and Heat Islands: Albedo, Evapotranspiration, and Anthropogenic Heat

1997-03-30 | Haider Taha
Haider Taha's paper, published in Energy and Buildings (Vol. 25, 1997), examines the characteristics of urban climates and the causes and effects of urban heat islands. The paper discusses the impacts of surface albedo, evapotranspiration from vegetation, and anthropogenic heating on near-surface climate conditions. Numerical simulations and field measurements indicate that increasing albedo and vegetation cover can effectively reduce surface and air temperatures near the ground. Urban climates differ from rural climates, with urban areas often experiencing higher temperatures, more cloud cover, and more precipitation. The urban heat island effect is a phenomenon where urban areas are significantly warmer than their rural counterparts. This effect is influenced by factors such as urban thermophysical properties, geometry, and anthropogenic heat, moisture, and pollutant sources. The paper highlights the importance of surface albedo in urban climates. Urban albedos typically range from 0.10 to 0.20, but can be higher in some cities. High-albedo materials can reduce solar radiation absorption, leading to cooler surfaces. Studies show that increasing albedo can lower air temperatures by up to 4°C in some cases. Evapotranspiration from vegetation is another key factor in urban climates. Vegetation can create cooler microclimates, known as oases, which are 2-8°C cooler than their surroundings. In urban areas, lower evapotranspiration rates contribute to higher daytime temperatures. Vegetation can reduce air temperatures by up to 2°C. Anthropogenic heating, from sources such as buildings and vehicles, also affects urban climates. While the magnitude of anthropogenic heating varies, it can contribute to the urban heat island effect. However, its impact is generally smaller compared to the effects of albedo and vegetation. The paper concludes that increasing urban albedo and vegetation can effectively reduce air temperatures and mitigate the urban heat island effect. Simulations suggest that reasonable increases in urban albedo can lead to a decrease of up to 2°C in air temperature, while increases in vegetation can result in a 2°C decrease. Under certain conditions, these reductions can reach up to 4°C. The study emphasizes the importance of urban planning and design in mitigating the urban heat island effect and improving urban climates.Haider Taha's paper, published in Energy and Buildings (Vol. 25, 1997), examines the characteristics of urban climates and the causes and effects of urban heat islands. The paper discusses the impacts of surface albedo, evapotranspiration from vegetation, and anthropogenic heating on near-surface climate conditions. Numerical simulations and field measurements indicate that increasing albedo and vegetation cover can effectively reduce surface and air temperatures near the ground. Urban climates differ from rural climates, with urban areas often experiencing higher temperatures, more cloud cover, and more precipitation. The urban heat island effect is a phenomenon where urban areas are significantly warmer than their rural counterparts. This effect is influenced by factors such as urban thermophysical properties, geometry, and anthropogenic heat, moisture, and pollutant sources. The paper highlights the importance of surface albedo in urban climates. Urban albedos typically range from 0.10 to 0.20, but can be higher in some cities. High-albedo materials can reduce solar radiation absorption, leading to cooler surfaces. Studies show that increasing albedo can lower air temperatures by up to 4°C in some cases. Evapotranspiration from vegetation is another key factor in urban climates. Vegetation can create cooler microclimates, known as oases, which are 2-8°C cooler than their surroundings. In urban areas, lower evapotranspiration rates contribute to higher daytime temperatures. Vegetation can reduce air temperatures by up to 2°C. Anthropogenic heating, from sources such as buildings and vehicles, also affects urban climates. While the magnitude of anthropogenic heating varies, it can contribute to the urban heat island effect. However, its impact is generally smaller compared to the effects of albedo and vegetation. The paper concludes that increasing urban albedo and vegetation can effectively reduce air temperatures and mitigate the urban heat island effect. Simulations suggest that reasonable increases in urban albedo can lead to a decrease of up to 2°C in air temperature, while increases in vegetation can result in a 2°C decrease. Under certain conditions, these reductions can reach up to 4°C. The study emphasizes the importance of urban planning and design in mitigating the urban heat island effect and improving urban climates.
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