Urban heat islands are frequently cited as a reason to install a cool roof, but the heat island effect is actually caused by a number of other factors in addition to darkcolored roofs. Luckily, since we know what causes the urban heat island effect, we can control it to a significant extent. Elevated global temperatures may thus be compounded by the additional stress resulting from the urban heat island. Techniques to reduce the urban heat island effect science. Forms and materials chapter pdf available january 2011 with 2,971 reads how we measure reads. Both the urban heat island and urban cold island effects are most intense at times of stable meteorological conditions. Uhi is most noticeable during the summer and winter. An interdisciplinary team of climatologists, meteorologists, geographers, engineers and public health experts have contributed to the study. Urban heat island t the majority of cities are sources o f heat and pollution and the thermal structure of the atmosphere abov e them is affected by the heat island effect. Jonathan winfrey, chris castro and zach bamman bsc 4932l. The heat island effect is a term used to describe higher air and structure temperatures in an urban setting as opposed to the lower temperatures found in more rural areas.
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. The higher temperatures experienced in urban areas compared to the surrounding countryside has enormous consequences for the health and wellbeing of people living in cities. Economic assessment of the urban heat island effect. Understanding the factors contributing to the urban heat island effect is reasonably straightforward. Heat islands can occur yearround during the day or night. 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. The temperature difference is much lower in winter. Many urban and suburban areas experience elevated temperatures compared to their outlying rural surroundings. Absorption of shortwave radiation from the sun in low albedo re. Certain techniques reduce the demand for air conditioning and reduce energy bills because the dark surfaces and low albedo of urban structures heat the area, the logical solution would be to reverse this trend.
The urban heat island effect has the following causes oke, 1987. This is the origin of the name of urban heat island. This temperature discrepancy is the result of a bizarre phenomenon known as the urban heat island effect. Local governments face challenges in adapting to urban heat, however, including the complexity of the choices available, limited resources and authority. A systematical study on uhi was carried in singapore 10. Urban rural temperature differences are often largest during calm, clear evenings. A heat island is bes t visualised as a dome of stagnant warm air over the heavily builtu p areas of cities emmanuel, 2005. The urban heat island uhi is a phenomenon that affects many millions of people worldwide. A tool kit for local governments introduction urban heat islands urban heat is a problem the earth is warming. The full sequence of lessons allows students to explore the abiotic concept 1 and biotic factors concept 2 involved in this phenomenon. The urban heat island effects can also be reduced by weather phenomona.
Pdf mitigating urban heat island effect by urban design. The urban heat island may also increase cloudiness and precipitation in the city. Any effective solution will certainly include a combination of measures, including cool pavements, cool roofs, increases in urban forests and green roofs. The temperature difference is larger at night than in the day, and larger in winter than in summer. Phoenix is hot but doesnt top urban heat island list. The abiotic lessons generally include opportunities for students to think. Find out what state and local entities across the country are doing to reduce the urban heat island effect. The main cause of the urban heat island effect is from the. Aug 03, 2018 the urban heat island effect is not a new phenomena, but countries like the uk are more exposed to the threats of extreme heat as summers get longer and hotter. Widespread surface changes can reduce the urban heat island effect, helping residents adapt to urban heat. There is a strong annual profile in the magnitude of the urban heat island effect, and most of the monthly variability can be explained by correlating wind speed and sky cover data to temperature differ. The increased use of manmade materials and increased anthropogenic heat. For example, the average summer temperature in fresno is about 84 f, and the urban heat island effect averages 4 f, which is a relatively modest increase over a hot background.
Urban heat island effect an overview sciencedirect topics. In the near future it is expected that the global rate of urbanization will increase by 70% of the present world urban population by 2030, as urban agglomerations emerge and population migration from rural to urban suburban areas. The effects of vegetative cooling and the urban heat island effect research by. The purpose of this project is to examine exactly how the infrastructure of an urban area contributes to significant temperature increases, to describe the impacts this effect has on these areas, and to determine solutions for this widespread problem. The urban heat island effect, its causes, and mitigation. Contributors to the urban heat island effect and the potential solutions to it vary enormously from city to city, which is why modelling of individual cities is vital.
Londons sizzling heat island is bad news for your sweaty. Mar 31, 2010 the effects of vegetative cooling and the urban heat island effect research by. However, several techniques can be employed by landscape architects to help. This makes a temperature difference, thus creating the effect called a heat island or more specifically an urban heat island. Compendium of strategies describes the causes and impacts of summertime urban heat islands and promotes strategies for lowering. The urban heat island effect uhi is a phenomenon whereby the concentration of structures and waste heat from human activity most notably air conditioners and internal combustion engines results in a slightly warmer envelope of air over urbanised areas when compared to surrounding rural areas. As the name implies, the effect makes cities into islands of heat. Six big cities in japan sapporo, sendai, tokyo, nagoya, kyoto, and. Usually, urban lands cities have a mean temperature 8 to 10 degrees more than the surrounding rural areas. The temperature difference between the city and surrounding areas is also a function of winds. Strong winds reduce the temperature contrast by mixing together the city and rural air.
Does urban heat island effect exaggerate global warming. Isotherms on a map show an urban area with higher temperatures emerging like a warm island floating on a cooler sea. How landscape architecture mitigates the urban heat island effect. Reflective roof surfaces can play a key role in reducing the heat island effect, but a multifaceted approach that accounts for other contributing factors will. These links can also be found on the syracuse university environmental finance center website. Environmental protection agency, temperatures in u. Paving over natural landscapes removes the cooling effect. Orangeville is a community with a population of less than 30. Causes of urban heat island formation urban heat island impacts on energy consumption, environmental quality, and human health resources for further information. Why are sydneys western suburbs heating up so much. Efforts in japan to mitigate the urban heat island effect.
The urban heat islands can be defined as any urban area which has the tendency to be warmer than a surrounding rurallesser developed area. Heat is created by energy from all the people, cars, buses, and trains in big cities like new york, paris, and london. For smaller cities, heat islands are less noticeable. Phoenix is among the second tier of cities affected by the heat island effect, according to a university of georgia study. Reducing the impact of extreme heat events in moreland by creating a cooler, greener more liveable city. How landscape architecture mitigates the urban heat island. Urban heat islands ucar center for science education. Jul 05, 2015 the urban heat island effect uhi is a phenomenon whereby the concentration of structures and waste heat from human activity most notably air conditioners and internal combustion engines results in a slightly warmer envelope of air over urbanised areas when compared to surrounding rural areas. This phenomenon is due to several factors that combine to alter the local microclimate of an urban area. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak.
Waste heat from vehicles, factories, and air conditioners may add warmth to their surroundings, further exacerbating the heat island effect. Paving over natural landscapes removes the cooling effect that plants have through. 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. Data from the camden area showed that the urban heat island effect is maximized in august. The urban heat island part 1 alevel geography aqa, ocr. The nighttime effect of uhis can be particularly harmful during a heat wave, as it deprives urban residents of the cool relief found in rural areas during the night. The urban heat island uhi effect describes a phenomenon in which temperatures in urban areas are markedly higher than those in surrounding areas.
Some of the earliest incident of heat islands were observed in late nineteenth century in cities such as london, paris, berlin and other european cities which were major centres of industrial activity. Vini halve team member project support team empri dr. In this science friday interview, listen to science friday associate producer alexa lim explain the urban heat island effect and talk to research ecologists rich hallett and nancy sonti at of the u. This phenomenon is known as urban heat islands uhi allen et al. Does urban heat island effect exaggerate global warming trends. The urban heat island effect is not a new phenomena, but countries like the uk are more exposed to the threats of extreme heat as summers. Certain techniques reduce the demand for air conditioning and reduce energy bills. Understanding basic contributors to the problem, however, is an important starting point. In the short run, the local officials can use these tools to cool individuals and to save. Measures to mitigate urban heat islands cool roofs and. Alterations of surface area, improper urban planning, air pollution, etc. Mitigating urban heat island effect by urban design. Learn about the five strategies to reduce the heat island effect. The warming effect of urbanisation has critical impacts on health and wellbeing, as well as human comfort and the local atmosphere grimmond, 2007.
Jun 16, 2017 this video explains urban heat islands the concept that cities are warmer than the surrounding countryside. Around half of the worlds human population lives in urban areas. Because the dark surfaces and low albedo of urban structures heat the area, the logical solution would be to reverse this trend. The uhi effect has significant consequences for the liveability in our cities, and is the source of a significant number of environmental problems in urban areas yang et al. However, several techniques can be employed by landscape architects to help combat the local rise. As an illustration of the relationship between progressive urbanization and urban heat island formation, a plot of the difference between average annual temperatures of orangeville, on, and toronto pearson airport is shown in fig. The use of geothermal energy and radiant cooling systems, are alternative solutions to.
The urban heat island effect is linked to the built environment and threatens human health during extreme heat events. Forest service in new york city about the role that urban trees can play in mitigating its effects. It thus constitutes a reference document for the implementation of local demonstration projects on urban heat island mitigation, for which calls for proposals are. An urban heat island, or uhi, is a metropolitan area thats a lot warmer than the rural areas surrounding it. This video explains urban heat islands the concept that cities are warmer than the surrounding countryside. Londons sizzling heat island is bad news for your sweaty office. No, this is a separate phenomenon where cities are 68f warmer than surrounding rural areas. This fact is known as the urban heat island effect. Urban heat island lesson plans background information pdf this urban heat island unit can be used in the classroom in a variety of ways. Oct 20, 2016 in this science friday interview, listen to science friday associate producer alexa lim explain the urban heat island effect and talk to research ecologists rich hallett and nancy sonti at of the u. This is especially felt in urban areas due to the urban heat island uhi effect, where temperatures can be 10of 5.
Any area rural, urban, or otherwise can experience the heat island effect, but urban areas are typically of more concern since they represent a more serious threat to local climate warming. Urban planning characteristics to mitigate climate change. Systems sustaina slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Final report on urban planning characteristics to mitigate climate change in context of urban heat island effect iii project duration august 1, 2016 to september 8, 2017 project team teri ms. Urban heat island in hong kong department of architecture, chinese university of hong kong page 7 of 24 in asia, numerous studies on the uhi have also been done in some countries. Urban heat islands are created in areas like these. Ozone can inflame the respiratory tract and increase the lungs susceptibility to. The temperature of urban areas can be significantly higher than that of the surrounding rural areas. Chow 9 reported the magnitude of the urban heat island effect in shanghai, china.
Linking science to april 2004 urban heat island and. Pdf high temperature in the city centers than its surroundings known as the urban heat island uhi effect, which is causing discomfort to the urban. A measurable increase in ambient urban air temperatures resulting primarily from the replacement of vegetation with buildings, roads, and other heat absorbing infrastructure. Higher temperatures attributed to the urban heat island effect increase the likelihood of nox and vocs forming smog, which has serious health consequences. With fewer trees in cities and large communities solar energy is more readily absorbed into manmade structures, causing higher urban area temperatures. In this study, the hourly air temperature differences between city hall urban and okoafo rural in lagos, nigeria, were calculated using one year of meteorological observations, from june 2014 to may 2015. Reduce urban heat island effect green infrastructure. Reduce urban heat island effect urban heat islands occur when cities replace natural land cover with dense concentrations of pavement, buildings, and other surfaces that absorb and retain heat. The urban cold island effect takes place in the early morning because the building within cities block the suns solar radiation, as well as the wind speed within the urban centre. Linking science to april 2004 urban heat island and climate. The uniformity of this island shaped pattern generally indicates a few depressions due to the presence of particularly hot points i. Therefore these maps do not reflect the total heat in each area, just the increase in temperature that is due to the urban heat island itself.
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