The Issue of the Urban Heat Island

For the first time in 2008 the human population was split evenly between urban and non-urban areas (Population Reference Bureau). Now, three years later, with greater than 50 percent of people live in urban areas, a large proportion of the human population is at risk of danger from urban climate stress. Urban areas drastically alter the natural landscape of the environments they replace and along with that, feed back loops that maintain local climate and ecosystems. The common identifiers of urban and suburban areas such as large buildings, blacktop surfaces, and roof tops not only directly affect the surfaces they replaced and the ecosystems the land supported, but also the stable climate that the land supported. Natural surfaces such as meadows and forests help to maintain local climates by performing multiple environmental services. When replaced by ubiquitous urban surfaces such as vast blacktop parking lots and roads the local evapotranspiration and albedo are reduced and heat-trapping environments are created (Buyantuyev and Jianguo, 2010). The high concentration of impervious low albedo surfaces in urban areas means that heat is more concentrated in those areas compared to their surrounding natural land. This phenomenon occurs in many urban settings and is known as the Urban Heat Island effect (UHI).

Since the Chinese government began its reform process in 1978, Shanghai, China has been constantly expanding and urbanizing. Past studies of the historical UHI in Shanghai have shown that the intensity of the UHI has increased from year to year along with increasing urban energy use and area of paved road and decreasing area of cropland (Zhang et al., 2010). In a study of the human health consequences of the UHI in Shanghai, Zhang et al. found that there is a correlation between the rising mortality rate from heat related illnesses in Shanghai and the increasing intensity and frequency of the UHI.

Although this research will be focused on the case of the Shanghai urban heat island, the methods and findings are applicable to all current and future cities that may experience the urban heat island effect. Understanding and mitigating the urban heat island effect is necessary for people in urban areas to maintain healthy living conditions and to prevent severe environmental pollution. With 50% of the world population and 78% of the US population now living in urban areas, it is very important that issues such as urban heat island effect be prevented to maintain a healthy global population and economy.

Purpose Statement

The purpose of this research paper is to investigate appropriate solutions to mitigate and prevent the urban heat island in Shanghai, China. Appropriateness will be determined by specific limitations and requirements of each strategy and how they fit in the context urban Shanghai. This method of determining suitability can be applied to other cities experiencing an urban heat island to investigate possible mitigation strategies.

Research Questions

1. What strategies are being developed and currently used to mitigate and prevent urban heat islands?

a. How have they succeeded in alleviating the urban heat island effect or preventing a heat island from forming?

b. What are their limitations and requirements (ie. Sunlight, space, soil quality, water, financing)?

2. What is the current composition of the land cover in Shanghai urban areas?

a. Is this data readily available or will the data need to be collected first hand?

3. Given the limitations and requirements of the investigated strategies, how can they be applied to Shanghai urban areas?

a. What solutions and mitigations strategies are currently being implemented and how successful are they?

Definitions of Key Terms

Urban Heat Island The UHI does not seem to be a well-defined term. A brief investigation of multiple research articles reveals that the phenomenon is generally describes an urban area that is relatively warm compared with its surrounding rural areas (USEPA, 2010; Zhang et al., 2011). Although many authors describe the temperature difference, there does not seem to be a definitive difference between urban and surrounding temperatures that defines a UHI. Depending on the time of day and season, differences between in temperatures in UHIs and surrounding areas can be anywhere from 2˚F to 22˚F. There are three distinct types of UHIs; surface, canopy, and boundary. Surface UHI describes the difference between temperatures at ground level in urban and surrounding rural areas. Boundary (above the skyline) and canopy (between surface and the skyline) UHIs are descriptors of atmospheric temperatures. Each type is useful in its own right (USEPA, 2010). Measures of surface UHI may be more appropriate for the purposes of my research because I am dealing with the human health consequences of the UHI. However, it will be necessary to determine what types of UHI are being measured by my sources of information.

Literature Review

Luke Howard first documented the effect of urban settings on urban and rural temperature differences in 1833 while studying the urban climate of London, England (Haffner and Kidder, 1998). Howard’s initial observations have developed into the theory of the urban heat island effect, now widely studied. Many factors contribute to the development of urban heat islands including low surface albedo, low moisture availability, lack of vegetation, building infrastructure, transportation, and local heat sources (Chen et al., 2008; Buyantuyev and Wu, 2009; Guha and Gober, 2007; Gober et al., 2010). These factors significantly influence urban climate by altering surface radiation and energy balance regimes, which can severely impact human and environmental health (Wu, 2008).

Features such as densely built tall buildings alter the energy balance by creating canyons that trap reradiated heat and, along with impermeable low albedo surfaces, increasing the urban albedo. The albedo of a surface is its ability to reflect solar radiation. High albedo surfaces tend to be lighter in color and reflect more solar radiation; therefore they are cooler. Low albedo surfaces are relatively darker and absorb a greater proportion of incoming solar radiation, as a consequence they are hotter. The low surface albedo of materials used to construct most tall buildings in urban areas causes them to absorb large amounts of solar energy during the day and slowly release it during the night. The high density and organization of these structures can prevent appropriate air movement within urban environments, further aggravating the heat-canyon effect (Buyantuyev and Wu, 2009).

Other low albedo surfaces ubiquitous in urban environments such as blacktop parking lots and roads, roofs, and sites cleared for development also lend themselves to heating the urban environment. Researchers have connected the low albedo of urban surfaces with the greater intensity of nighttime temperatures in urban heat islands. Since the rapid urbanization it experienced in the mid 20th century the urban average daytime temperature in Phoenix, Arizona has increased by 3.1(C and the average nighttime temperature has increased by 5(C (Buyantuyev and Wu, 2009; Tan et al., 2010). These urban heat-traps have severe consequences for human and environmental health.

Urban heat islands have been shown to increase the frequency and intensity of heat waves in urban areas. In 2005 a heat wave that lasted 5 days increased the mortality rate in the city by 85% and was 2 times higher than surrounding suburban areas (Tan et al., 2010). Páldy et al. explains that the main dangers of greater frequency and intensity of heat waves is posed to individuals at risk for cardiovascular, cerebrovascular, and respiratory diseases (2005). Researchers in Shanghai, Italy, and Budapest have found similar correlations between heat waves exacerbated by urban heat island and human mortality (Páldy et al., 2005; Tan et al., 2010). Tan et al. investigated the association between mortality during heat waves and living environment and found that during heat waves people in urban areas were at a greater risk of mortality from respiratory or circulatory system failure than people in rural areas (2010). Similar results were found in Budapest where a projected 5(C increase in the average daily temperature would increase the mortality rate by 10.6% (Páldy et al., 2005). High temperatures in cities have been associated with increased Ozone concentration, which has been shown to work synergistically with high temperatures to put residents at a higher risk for death from respiratory causes (PSR, 2009).

The same factors that put human residents in urban areas at risk also threaten environmental health. Higher temperatures in cities such as Phoenix, Arizona have resulted in increased water usage (Guhathakurta and Gober, 2007). Residents in urban areas of Phoenix use more water to counter the greater than average temperatures mainly by filling swimming pools and spraying hot surfaces such as pavement. Increasing water usage can result in drought and greater pollution of waterways. With increasing surface temperatures and increasing water use more and more thermal pollution of waterways has been observed. Any runoff from a vast heated surface such as a mall parking lot can severely raise the temperature of the body of water that it is draining into. Rising temperatures in water bodies can endanger aquatic life. Impermeable surfaces such as parking lots also cause greater volumes of water to flow directly into waterways at high velocities. When runoff is flowing fast it picks up trash and debris and erodes surfaces at a faster rate than usual. Such impermeable low albedo surfaces can make aquatic ecosystems inhospitable to native organisms and can threaten the health of people living near by.

Among the research that has investigated the issue of urban heat islands, various methods have been used to measure urban temperatures. A wide variety of methods are used because there is little agreement on what aspect of the urban heat island should be measured for a valid analysis. This is a difficult topic to reconcile because there are various parts to an urban heat island. An urban heat island profile can be divided into the surface layer, the canopy layer (between building rooftops and the ground), and the boundary layer (Weng et al. 2003). The distinction between which layer you are measuring is very important because there can be a dramatic difference in temperature between the three. One study found a 20(C difference between surface and air temperature. Surface temperature measurements are most relevant to issues of urban runoff and human health, where as the canopy and boundary layer temperatures are more relevant to urban weather patterns. Surface and canopy temperatures are easily measured in situ, or on site, by taking measurements manually. The majority of geographic temperature data reflects surface and surface or canopy temperatures because it has been the easiest means of collecting data. In other research this type of data has been collected using in person measurements using digital thermometers (Zhang et al., 2009), or using remote sensing stations (Jianguo et al., 2008) be collected using With the advent of remote sensing and GIS software a wealth of data is now available for boundary layer measurements.

Just as in other urban settings, research has shown a correlation between urbanization and the development of an urban heat island in Shanghai, China (Zhang et al., 2009). By comparing urban and rural temperatures from 1959 various researchers have shown that the difference in temperatures between urban and rural areas has increased along with urban development. Research shows that from 1959 to 2001 the variation between urban and rural temperatures increased by 0.21% per decade. These changes in the Shanghai urban climate are predicted to have severe consequences for residents (Tan et al., 2010).

Various mitigation strategies have been proposed to counter the effects of the urban heat island. Some strategies focus on improving shading and evapotranspiration in urban settings by planting vegetation such as trees and shrubs. Such vegetation would increase the albedo of dense urban areas, slow down and absorb runoff, provide shade, and balance energy exchange with the atmosphere through evapotranspiration. Other solutions involve developing watered landscapes in urban areas. Irrigated landscapes hold less and reflect more heat energy than problematic urban surfaces such as buildings and blacktop. Another strategy is to change the albedo of urban surfaces such as buildings to reflect more solar radiation. This strategy would help to reduce the amount of heat energy stored by urban surfaces and as a result it would reduce the intense nighttime urban heat island.

Research that has explored the relationship between urbanization and urban/rural temperature disparity in Shanghai, China for the most part have used in situ data. It may be useful to observe this relationship by through remotely sensed data. This method of analysis may allow the results to be used more generally to determine the risks for residents of Shanghai. Remotely sensed data measures the boundary level temperatures of a city, therefore this study would be more applicable to the greater weather patterns in the Shanghai urban area. There is also a lack of proposed solutions to mitigate the specific Shanghai urban heat island. It is necessary to observe the severity of the urban heat island in Shanghai as well as current urban land cover to assess the appropriateness of individual mitigation strategies.

Understanding the severity of the urban heat island in Shanghai and determining what solutions are appropriate for its particular urban setting is directly consequential to the residential populations quality of life and wellbeing. Reducing the intensity of the urban heat island may reduce the mortality rate in the event of a heat wave. Possible mitigation strategies would provide comfortable climates in urban areas, reduce energy usage, and minimizes environmental pollution from urban runoff.

Methods

The chief objective of the proposed research is to assess the potential for urban heat island mitigation strategies and solutions in Shanghai, China. This analysis will require two phases of research to achieve the stated objective. In order to facilitate thorough and careful research, the three research questions have been translated into a set of corresponding research objectives:

1) What strategies are being developed and currently used to mitigate and prevent urban heat islands?

a) Compile a list of proven mitigation strategies and solutions.

b) Determine how successful each strategy has been in achieving its objectives of mitigating or preventing the urban heat island effect.

c) Determine each strategies limitations and requirements. Using this list, establish what data; in addition to land cover needs to be collected.

2) What is the current composition of the land cover in Shanghai urban areas?

a) Determine how land cover and other relevant data will be collected (ie. Over the internet, using remote sensing, physical collection of the data)

b) Collect, aggregate, and validate land cover and other relevant data.

3) Given the limitations and requirements of the investigated strategies, how can they be applied to Shanghai urban areas?

a) Determine the suitability of the Shanghai urban area for the investigated strategies.

First, after compiling a list of proven strategies, a meta-analysis of potential mitigation strategies will be carried out. Next, land cover and other pertinent data for the Shanghai urban area will be collected and aggregated. To determine whether these strategies are appropriate for Shanghai and to what extent they can be implemented, the characteristic requirements of each investigated strategy will be tested against the characteristics of the Shanghai urban area.

Meta-Analysis

There are numerous different strategies currently being used to combat urban heat islands as well as many others that are being developed and tested. All these different strategies will form our target population for the meta-analysis. In order to provide a comprehensive but not exhaustive base for meta-analysis, the four general mitigation strategies defined by the US Environmental Protection Agency on their urban heat island mitigation page will be used as a sampling frame. These strategies are: trees and vegetation, green roofs, cool roofs, and cool pavements. Using this list to direct the meta-analysis, three examples of each will be collected from online and literature resources. Three case studies will be sufficient to provide a substantial amount of information on each strategy and to be confident of its usefulness. When these examples are being collected, careful attention will be paid to how successful each has been. In order to avoid error in the data collection process, examples will be chosen based on the amount and reliability of the information available. Examples will not be collected explicitly because they are successful cases.

Next, the collected examples will analyzed for (1) their success in mitigating or preventing the urban heat island effect, (2) spatial requirements and constraints, and (3) abiotic requirements and constraints. The resulting constraints and requirements will determine what data needs to be collected on the Shanghai urban area. These requirements and constraints for each strategy will later be applied to data collected on Shanghai to identify sites where these strategies could be implemented. Collecting this data will take a relatively short period of time.

GIS Data Collection

In order to collect pertinent data, the method of collection will first be determined. An initial search of the Internet for land cover and other needed data will be performed. If the necessary data is available over the Internet by search or request, the data will be collected in a geo-database and edited using ArcGIS to create a comprehensive profile of the Shanghai urban area. If all or some of the data is not available over the Internet or by special request the data will need to be collected using remote sensing techniques. Some data that may be needed might include high spatial resolution land cover, altitude, and vegetative cover data.

Once the data has been collected it can be aggregated using Clark Labs’ GIS program, IDRISI Taiga. This process will include using multiple tools in the program resulting in individual map layers representing factors such as of the spatial distribution of the urban area, land cover, and other necessary data.

This data will then be validated by research participants using face validation techniques. Land cover data will be validated by comparing the computer’s coding of land cover data to an observer’s coding of the same land cover data. Pixels of land cover data will be randomly selected and assessed. Validation of other data may require in field measurements and observations to be taken and compared against the remotely sensed data.

Determining Suitability

Once individual profiles of the four types of mitigation strategies and a profile of the Shanghai urban area have been created, the strategies will be tested for their suitability within urban Shanghai. This assessment will be accomplished using the GIS software IDRISI Taiga’s multi-criterion evaluation (MCE) module. In order to use the MCE module, raster images indicating the limitations and requirements of each strategy must first be created. Once these files have been created the will be entered into the MCE module and each requirement will be weighted appropriately if weighting is deemed necessary. The resulting raster images will then be compared to a true color map of Shanghai to reveal what areas are appropriate for such strategies. These results can then be used to inform future decisions to implement urban heat island mitigation strategies within the Shanghai urban area.

Concluding Remarks

This research is extremely important to securing the safety of human and environmental health not only in Shanghai, China, but in all populated areas across the world. The strategies that will be investigated through this research are adaptable to existing cities facing the consequences of urban heat islands as well as for developing cities that could potentially face this issue in the future. It is important for cities such as Shanghai that continue to expand its urban area to build these mitigation strategies into their future plans and existing infrastructure. This will directly affect the livelihoods of the cities residents by protecting their own health as well as that of the ecosystem that supports their everyday lives. Understanding what factors that constrain these strategies and how to assess their suitability to a site such as Shanghai will be useful in future investigations and applications on the topic of urban heat islands

Works Cited

Buyantuyev, Alexander and Wu, Jianguo. 2010. “Urban heat islands and landscape heterogeneity: linking spatiotemporal variations in surface temperatures to land-cover and socioeconomic patterns”. Landscape Ecology, issue 25: 17-23. http://www.springerlink.com/content/xp40247307lr3436/fulltext.pdf

Chen, Liding; Fu, Bojie; Zhao, Wenwu. 2008. Source-Sink Landscape Theory and its Ecological Significance. http://www.springerlink.com/content/a512831874j0x28r/fulltext.pdf.

Gober, Patricia; Brazel, Anthony; Quay, Ray; Myint, Soe; Grossman-Clarke, Susanne; Miller, Adam; Rossi, Steve. 2010. Using Watered Landscapes to Manipulate Urban Heat Island Effects. Journal of the American Planning Association, Winter 2010, Vol. 76, No. 1.

Guhathakurta, Subhrajit and Gober, Patricia. 2007. The Impact of the Phoenix Urban Heat Island on Residential Water Use. Journal of American Planning, Summer 2007, Vol. 73, No. 3.

Haffner, Jan and Kidder, Stanley Q. 1998. Urban Heat Island Modeling in Conjunction with Satellite-Derived Surface/Soil Parameters. http://amsu.cira.colostate.edu/kidder/UHI.pdf.

Howard, L. (1833). The climate of London, vols. I – III. London: Harvey and Dorton.

Páldy, A.; Bobvos, J.; Vámos, A; Kovats, R.S.; Hajat, S. 2005. The Effect of Temperature and Heat Waves on Daily Mortality in Budapest, Hungary, 1970 – 2000. http://www.springerlink.com/content/ql2543240u1ltku7/fulltext.pdf

Physicians for Social Responsibility (PSR). 2009. Health Implications of Global Warming: Heat’s Deadly Effects. http://www.psr.org/assets/pdfs/heats-deadly-effects.pdf

The Population Reference Bureau. 2009. Human Population: Urbanization. http://www.prb.org/Educators/TeachersGuides/HumanPopulation/Urbanization.aspx

Tan, Jianguo; Zheng, Youfei; Tang, Xu; Guo, Changyi; Li, Liping; Song, Guixiang; Zhen, Xinrong; Yuan, Dong; Kalkstein, Adam J.; Li, Furong; and Chen, Heng. 2008. The Urban Heat Island and Its Impact on Heat Waves and Human Health in Shanghai, China. Int J Biometeorol (2010), issue 54:75–84. http://www.springerlink.com/content/m256t0413674whl1/fulltext.pdf

Tan, Jianguo; Zheng, Youfei; Tang, Xu; Guo, Changyi; Li, Liping; Song, Guixiang; Zhen, Xinrong; Yuan, Dong; Kalkstein, Adam J.; Li, Furong; and Chen, Heng. 2010. The Urban Heat Island and Its Impact on Heat Waves and Human Health in Shanghai, China. http://www.springerlink.com/content/m256t0413674whl1/fulltext.pdf.

US Environmental Protection Agency (EPA). 2010. Reducing Urban Heat Islands: Compendium of Strategies. http://www.epa.gov/heatisld/resources/pdf/BasicsCompendium.pdf

Weng, Qihao; Lu, Dengsheng; Schubring, Jacquelyn. 2003. Estimation of land surface temperature–vegetation abundance relationship for urban heat island studies. http://www.utsa.edu/lrsg/Teaching/EES5053_Geo4093/Labs/Wengetal.pdf

Wu, Jianguo. 2008. Making the Case for Landscape Ecology. http://leml.asu.edu/jingle/web_pages/wu_pubs/pdf_files/2008-wu-urbansust.pdf.

Zhang, Kaixuan; Wang, Rui; Shen, Chenchen; Da, Liangjun. 2008. “Temporal and Spatial Characteristics of the Urban Heat Island During Rapid Urbanization in Shanghai, China.” Environmental Monitoring and Assessment (2010), issue 169: 101-112. http://www.springerlink.com/content/l308379r70t16601/fulltext.pdf

Zhang, Kaixuan; Wang, Rui; Shen, Chenchen; and Da, Liangjun. 2009. Temporal and Spatial Characteristics of the Urban Heat Island During Rapid Urbanization in Shanghai, China. http://www.springerlink.com/content/l308379r70t16601/fulltext.pdf
Spatial Analysis of Shrinking U.S. Neighborhoods, 2000-2009
Clark University
Budget Justification Page

A. Senior Personnel – Dr. Hamil Pearsall (PI) will dedicate 4 summer months during each of the three years of the project.

B. Other Personnel – One BA student at Clark University will work closely with Dr. Johnson in the data analysis and management. This student will work for 12 months, full-time.

C. Fringe Benefits: Clark University’s federally approved fringe rate is 43% for faculty and 11.1% for students.

E. Travel – Costs for Dr. Pearsall to present research findings at annual Association of American Geographer’s Annual meetings in the spring 2012. Travel costs also for Dr. Pearsall and one student to present research findings at 2012 and 2013 annual meetings of the New England – Saint Lawrence Valley Geographical Society at a location within New England to be determined. Costs will be incurred to travel to Shanghai, China for 1 month to conduct field research in the summer of 2010.

Below are the expected travel expenses to the 2013 AAG conference:
Boston to conference location roundtrip $300
Four night lodging @ $150 per night $600
Per diem 5 days @ $40 day $200
Transportation to/from airports Boston @ $35 * 2 $70 Washington @ $35 * 2 $70
Registration Fee $300
Total AAG conference travel = $1,540

Below is the per person expected travel expenses to the local conference:
Automobile mileage $150
Meals $15
Registration $200
Total local conference travel = $365 x 2 participants = $730 in Year 2 and Year 3 each

Below are the expected travel expenses to Shanghai, China to conduct field research.

Boston to field research location roundtrip $1775
Three weeks lodging @ $140 per night $2940
Per diem 3 weeks @ $40 day $840
Transportation to/from airports Boston @ $60 round trip $60 Shanghai @ $20 round trip $20
Total research travel = $5635 per person * 2 = $11,270 in year 3

G. Other Direct Costs
1. Materials and Supplies – Two portable netbooks ($300) for field research are needed. Funds are also requested ($5000) to purchase GPS units for field data collection. Funds are requested to purchase IDRISI GIS software and supplies ($3000) to facilitate Mapping.

I. Indirect Costs: Calculated at Clark University’s federally approved indirect cost rate of 52% of Modified Total Direct Costs, for a total of $58,275.08.