The temperature of urban areas can be significantly higher than that of the surrounding rural areas. The summer urban heat island uhi effect is a daytime elevation in the outdoor urban air temperature that results in part from the replacement of trees and other vegetation with buildings, roads and other heat absorbing infrastructure causes. Fractal analysis of satellitedetected urban heat island. Oke department of geography, university of british columbia, vancouver, b. The impact of the urban heat island effect on temperature is widely documented. Closed isotherms indicating an area that is relatively warm. The development of an urban heat island is a timevarying process involving the physical geography. By interministry coordination committee to mitigate urban. The presence of any area warmer than its surrounding landscape. Environmental protection agency s office of atmospheric programs subject. Urban planning characteristics to mitigate climate change. Urban heat island in hong kong department of architecture, chinese university of hong kong page 4 of 24 period.
The highest values of the urban heat island intensity, in the region of 38 c, are often reached between about 11 oclock at night and 3 oclock in the morning figure 2. View urban heat island research papers on academia. Urban heat island monitoring and analysis using a nonparametric. The weaker the wind velocity, the greater the heat island. Around half of the worlds human population lives in urban areas. This one will be about urban heat islands in atlanta, but what is true for atlanta is true for new york city. A summary for decision makers introduction this is the summary report of a technical study, commissioned by the mayor to investigate londons urban heat island. Causes of urban heat island phenomenon causes of urban heat island phenomenon are. Linking science to april 2004 urban heat island and. A specific measure of this effect is the intensity of the difference between the maximum urban temperature and the minimum rural temperatureiii. Effects of urban heat island on air pollution concentrations.
Strong winds reduce the temperature contrast by mixing together the city and rural air. No, this is a separate phenomenon where cities are 6. Uhi intensities are also greater in summer than winter because of figure 1. A comprehensive statistical study on daytime surface urban heat. Counteracting urban heat island effects in a global climate. Buildings, roads, and other infrastructure replace open land and vegetation. Uhis therefore exist, to lesser or greater extents, across the whole landscape. Try to find the balance in combine urban green space system and other techniques. As warming associated with urban development and climate. An urban heat island, or uhi, is a metropolitan area thats a lot warmer than the rural areas surrounding it. Uhi is most noticeable during the summer and winter.
Urban heat island effect is observed would show heat radiating at night and higher early morning temperatures. Fractal analysis of satellitedetected urban heat island effect qihao weng abstract surface radiant temperatures derived from landsat tm thermal infrared images of december, 1989, 03 march, 1996, and 29 august 1997 were used to study the urban heat island uhi phenomenon in. Urban heat islands are also common over the cities of even fairly. As it would be expected, there is a relatively minor knowledge about non urban heat islands, since they usually do not represent a risk for the human being or the environment. Planning urban heat island mitigation in boston executive summary erin coutts, kate ito, cecilia nardi, trang vuong to advance important resilience objectives, in 2015 the trust for public land, the city of boston, and a variety of partners launched a twoyear pilot project to inform and catalyze green infrastructure work in the metropolitan boston.
Moreover, parametric statistical analyses, such as regression and. This study focuses on the uhi that exists in the city of melbourne, largely due to the high concentration of heat. Elevated global temperatures may thus be compounded by the additional stress resulting from the urban heat island. An urban heat island uhi is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. At each scale, the uhi is derived by different elements e. This document is available in its entirety in electronic format pdf on the. The temperature difference between the city and surrounding areas is also a function of winds. Pdf city size and the urban heat island researchgate. This uhi can be defined at three spatial scales, including the building, neighborhood, and cityregionscale. Givoni 1998 mentioned that the largest elevations of the urban temperatures occur during clear and stillair nights. Urban heat island uhi has become one of the worlds leading urban environmental issues. The urban heat island may also increase cloudiness and precipitation in the city. The top 10 cities with the most intense summer urban heat islands average daily urbanrural. This reduces the urban heat island intensity to a daytime minimum figure 2c and may even generate an urban cool island.
Pdf the urban heat island uhi is defined as the temperature difference between the urban and suburban areas and rural areas in the same. Urban heat islands uhis have a significant and negative impact on the urban ecological environment and on human health, and it is imperative to examine factors that lead to uhis. Probability density functions pdf for 4 selected cities are presented in fig. Although numerous studies have been conducted in this field, little research has considered seasonal variations in uhis in coastal cities. City size and the urban heat island article pdf available in atmospheric environment 1967 78. Final report on urban planning characteristics to mitigate climate change in context of urban heat island effect 5. Examining seasonal effect of urban heat island in a. This fact is known as the urban heat island effect. Think about the relief provided by sidewalk trees or the vegetation of a playground. High temperature in the city centers than its surroundings known as the urban heat island uhi effect, which is causing discomfort to the urban dwellers in the summer time is gaining much attention around the world because the world is getting urbanized as it advances in technology. Urbanization has increased concerns about the uhi, particularly in terms of human health and a healthy environment. The urban heat island phenomenon is a consequence of many factors. A recent study by the american geophysical union found that temperatures in urban areas like atlanta, georgia and houston, texas were artificially raised by as much as 10 degrees in.
The urban heat island represents the higher temperatures associated with urban spaces as compared with rural areas. Mitigate urban heat island reduce anthropogenic heat from buildings and transport. Even the case of tampa is not entirely incompatible with that view because there in winter are 12 percent more sunshine hours than in summer. Urban heat islands are created in areas like these. Pdf urban heat island towards urban climate researchgate. By combining land use data with spatially explicit surface. This was achieved by combining the dates of start of construction for different new. The urban heat island intensity is stronger in the nighttime 03, 21 lst than in the daytime 09, 15 lst, exhibiting a.
Some specific causes of urban heat island include manmodified landscape example. A comparison of the temperature in the city of baltimore with. An urban heat island has been best described as a dome of stagnant warm air over the heavily builtup areas of the city 4. Due to urbanisation, many surfaces become impermeable. A gis extension model to calculate urban heat island. Combining vegetation and water installations waterfalls, fountains and. The urban heat island effect in winnipegsept262007final. An urban heat island will exist to an extent whenever an area contains more heat absorbing materials than surrounding areas. Impact of urban heat island on regional atmospheric pollution. The average maximum urban heat island intensity over the oneyear period is 2. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. The urban heat island effects can also be reduced by weather phenomona. Economic assessment of the urban heat island effect.
Evaluation of urban heat island mitigation strategies for. At times, the urban heat islands of two nearby urban areas merge, affecting the climate of the region. There is a clearly identifiable urban heat island in camden, new jersey, apparent in both the satellite images and climate data. The properties of urban roofs and pavements, as well as human activity, contribute to the formation of summer noglossary urban heat islands no. The main cause of the urban heat island effect is from the modification of. This phenomenon is known as urban heat islands uhi allen et al. Wrf urban canopy model we use the weather research and forecasting wrf model version 3. This is why the urban heat island is often referred to as a nighttime phenomenon. An energy and comfort comparison between passive cooling and mitigation urban heat island techniques for residential buildings in the mediterranean region. Heat is created by energy from all the people, cars, buses, and trains in big cities like new york, paris, and london. An interdisciplinary team of climatologists, meteorologists, geographers, engineers and public health experts have contributed to the study. New surfaces should employ materials that combine greater reflectance and a low. The clearer the sky the greater is the development of the city temperature. As urban areas develop, changes occur in the landscape.
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