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. The urban heat island uhi is a phenomenon that affects many millions of people worldwide. The urban heat island part 1 alevel geography aqa, ocr. 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. Data from the camden area showed that the urban heat island effect is maximized in august. As the name implies, the effect makes cities into islands of heat. 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. Absorption of shortwave radiation from the sun in low albedo re.
The urban heat island effects can also be reduced by weather phenomona. Many urban and suburban areas experience elevated temperatures compared to their outlying rural surroundings. 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. Alterations of surface area, improper urban planning, air pollution, etc. Mar 31, 2010 the effects of vegetative cooling and the urban heat island effect research by. 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. The urban heat islands can be defined as any urban area which has the tendency to be warmer than a surrounding rurallesser developed area. Usually, urban lands cities have a mean temperature 8 to 10 degrees more than the surrounding rural areas. 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. Urban heat islands ucar center for science education. Strong winds reduce the temperature contrast by mixing together the city and rural air. Jun 16, 2017 this video explains urban heat islands the concept that cities are warmer than the surrounding countryside.
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. An interdisciplinary team of climatologists, meteorologists, geographers, engineers and public health experts have contributed to the study. Does urban heat island effect exaggerate global warming trends. The urban heat island effect is linked to the built environment and threatens human health during extreme heat events. 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. 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. 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. Paving over natural landscapes removes the cooling effect. The full sequence of lessons allows students to explore the abiotic concept 1 and biotic factors concept 2 involved in this phenomenon. Certain techniques reduce the demand for air conditioning and reduce energy bills. 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. A heat island is bes t visualised as a dome of stagnant warm air over the heavily builtu p areas of cities emmanuel, 2005. Economic assessment of the urban heat island effect.
How landscape architecture mitigates the urban heat island. This video explains urban heat islands the concept that cities are warmer than the surrounding countryside. However, several techniques can be employed by landscape architects to help combat the local rise. The abiotic lessons generally include opportunities for students to think. Isotherms on a map show an urban area with higher temperatures emerging like a warm island floating on a cooler sea. A tool kit for local governments introduction urban heat islands urban heat is a problem the earth is warming. Does urban heat island effect exaggerate global warming. This phenomenon is due to several factors that combine to alter the local microclimate of an urban area.
Linking science to april 2004 urban heat island and. The main cause of the urban heat island effect is from the. The temperature difference is larger at night than in the day, and larger in winter than in summer. 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.
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. It thus constitutes a reference document for the implementation of local demonstration projects on urban heat island mitigation, for which calls for proposals are. 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. Waste heat from vehicles, factories, and air conditioners may add warmth to their surroundings, further exacerbating the heat island effect. 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. Causes of urban heat island formation urban heat island impacts on energy consumption, environmental quality, and human health resources for further information.
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. The urban heat island effect has the following causes oke, 1987. Ozone can inflame the respiratory tract and increase the lungs susceptibility to. Efforts in japan to mitigate the urban heat island effect. Systems sustaina slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. The urban heat island uhi effect describes a phenomenon in which temperatures in urban areas are markedly higher than those in surrounding areas. Luckily, since we know what causes the urban heat island effect, we can control it to a significant extent. Phoenix is hot but doesnt top urban heat island list. Measures to mitigate urban heat islands cool roofs and. The urban heat island effect, its causes, and mitigation. 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.
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. 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 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 temperature difference is much lower in winter. Paving over natural landscapes removes the cooling effect that plants have through. In the short run, the local officials can use these tools to cool individuals and to save. Urban rural temperature differences are often largest during calm, clear evenings.
Londons sizzling heat island is bad news for your sweaty office. 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. This makes a temperature difference, thus creating the effect called a heat island or more specifically an urban heat island. 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. An urban heat island, or uhi, is a metropolitan area thats a lot warmer than the rural areas surrounding it. Compendium of strategies describes the causes and impacts of summertime urban heat islands and promotes strategies for lowering. Londons sizzling heat island is bad news for your sweaty. The use of geothermal energy and radiant cooling systems, are alternative solutions to. Higher temperatures attributed to the urban heat island effect increase the likelihood of nox and vocs forming smog, which has serious health consequences. Any effective solution will certainly include a combination of measures, including cool pavements, cool roofs, increases in urban forests and green roofs. Pdf mitigating urban heat island effect by urban design. 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. 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.
Forms and materials chapter pdf available january 2011 with 2,971 reads how we measure reads. Six big cities in japan sapporo, sendai, tokyo, nagoya, kyoto, and. 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. Local governments face challenges in adapting to urban heat, however, including the complexity of the choices available, limited resources and authority. Vini halve team member project support team empri dr. Find out what state and local entities across the country are doing to reduce the urban heat island effect. Urban heat island effect an overview sciencedirect topics. No, this is a separate phenomenon where cities are 68f warmer than surrounding rural areas. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. However, several techniques can be employed by landscape architects to help. This is the origin of the name of urban heat island. Understanding the factors contributing to the urban heat island effect is reasonably straightforward. The uniformity of this island shaped pattern generally indicates a few depressions due to the presence of particularly hot points i. A systematical study on uhi was carried in singapore 10.
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. Elevated global temperatures may thus be compounded by the additional stress resulting from the urban heat island. The increased use of manmade materials and increased anthropogenic heat. 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. The temperature difference between the city and surrounding areas is also a function of winds. The warming effect of urbanisation has critical impacts on health and wellbeing, as well as human comfort and the local atmosphere grimmond, 2007. Environmental protection agency, temperatures in u. Reducing the impact of extreme heat events in moreland by creating a cooler, greener more liveable city. Mitigating urban heat island effect by urban design. Linking science to april 2004 urban heat island and climate. Around half of the worlds human population lives in urban areas. The urban heat island may also increase cloudiness and precipitation in the city.
Orangeville is a community with a population of less than 30. This temperature discrepancy is the result of a bizarre phenomenon known as the urban heat island effect. Understanding basic contributors to the problem, however, is an important starting point. For smaller cities, heat islands are less noticeable. Reduce urban heat island effect green infrastructure. Urban heat islands are created in areas like these. Both the urban heat island and urban cold island effects are most intense at times of stable meteorological conditions. The effects of vegetative cooling and the urban heat island effect research by. Widespread surface changes can reduce the urban heat island effect, helping residents adapt to urban heat. Techniques to reduce the urban heat island effect science.
This phenomenon is known as urban heat islands uhi allen et al. This is especially felt in urban areas due to the urban heat island uhi effect, where temperatures can be 10of 5. Chow 9 reported the magnitude of the urban heat island effect in shanghai, china. Because the dark surfaces and low albedo of urban structures heat the area, the logical solution would be to reverse this trend. Urban planning characteristics to mitigate climate change. Heat islands can occur yearround during the day or night. Jonathan winfrey, chris castro and zach bamman bsc 4932l. These links can also be found on the syracuse university environmental finance center website. This fact is known as the urban heat island effect. 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. With fewer trees in cities and large communities solar energy is more readily absorbed into manmade structures, causing higher urban area temperatures. Learn about the five strategies to reduce the heat island effect. Uhi is most noticeable during the summer and winter.
Heat is created by energy from all the people, cars, buses, and trains in big cities like new york, paris, and london. 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. 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. Urban heat island lesson plans background information pdf this urban heat island unit can be used in the classroom in a variety of ways. A measurable increase in ambient urban air temperatures resulting primarily from the replacement of vegetation with buildings, roads, and other heat absorbing infrastructure. 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. The temperature of urban areas can be significantly higher than that of the surrounding rural areas. How landscape architecture mitigates the urban heat island effect. Forest service in new york city about the role that urban trees can play in mitigating its effects. Why are sydneys western suburbs heating up so much.