The Urban Heat Island

Jacob Chen

In my individual chapter, I will focus on Urban Heat Islands and I will discuss the definition of an Urban Heat Island, the impact of this phenomenon, the measures taken, and the future plans. Increasing urbanization has led to a growing urban heat island effect, which has serious implications for the regional environment and human health.

High-resolution Images:

Temperature (1.0 MB JPEG)
Vegetation (1.0 MB JPEG)

https://earthobservatory.nasa.gov/images/6800/new-york-city-temperature-and-vegetation

Background

The current research on the urban heat island effect is based on radiation temperatures obtained from satellite remote sensing, but the general public's understanding of urban heat island is relatively weak, so it is particularly important to investigate the impact of this phenomenon, to understand how to prevent it and to increase awareness of it in this deteriorating environment. “Scientists first discovered the heat island effect in the 19th century, when they observed that cities were warmer than the surrounding rural areas. Particularly in summer, asphalt, concrete, and other materials make up urban surfaces - also known as "impermeable surfaces". During the day, more solar radiation is absorbed, and at night, most of the heat is released into the urban air, creating warm bubbles on the city, which can be more intense than in rural areas of the city”。（Ecosystem, Vegetation Affect Intensity of Urban Heat Island Effect）

The definition and formed

“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 is usually larger at night than during the day and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the urban heat island effect is the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas”.（What is urban heat island). So why do urban heat islands form? “There are several reasons for the formation of urban heat islands.1: The influence of various artificial heat sources in the city. As urbanization continues to accelerate, the amount of energy required for industrial production, transport, social entertainment, and residential life is increasing day by day, emitting large amounts of heat into the atmosphere day and night; the increasingly dense urban population has also led to a sharp increase in energy-intensive equipment such as air conditioners and cars, which are like "little suns" heating up the surrounding The natural substrate of the city, such as green spaces, woods, and water bodies, is shrinking and diminishing. 2: Man-made buildings not only absorb heat very easily, but they also have a small thermal capacity. This means that they require relatively little heat to increase their temperature. Under the same intensity of sunlight, buildings in the city heat up much faster than natural substrates such as green areas and water bodies in the suburbs, and the surface temperature of buildings is significantly higher than the surface temperature in the suburbs. 3: The city center is full of tall buildings and there is no extra space for the heat to escape from the buildings, making the whole city like a large closed oven, which makes it very easy for the temperature to rise.” (Causes, Effects and Solutions To Urban Heat Island)

Deaths Classified as “Heat-Related” in the United States, 1979–2018

“Climate Change Indicators: Heat-Related Deaths.” US EPA, 2 Aug. 2022, www.epa.gov/climate-indicators/climate-change-indicators-heat-related-deaths.

The Impact

The 'urban heat island phenomenon can have an impact on local weather conditions, causing an increase in meteorological activity such as precipitation and thunderstorms. “For urban ecosystems, increased temperatures can lead to negative fluctuations, resulting in the reduction or loss of animal habitats and the replacement of existing species by invasive species. With global climate change, the 'urban heat island' is compounded by the constant occurrence of 'heat waves", which not only increase the temperature of the 'heat wave', but also prolong the duration of the 'heat wave'. "The impact on the health of urban dwellers can be immediate and even fatal. In addition, urban heat islands have a negative impact on the food and water supply within the city limits. For example, urban buildings have significantly warmer surface temperatures than their surroundings, and rainwater then runs off these hotter buildings, warming in the process. This warmer runoff flows into nearby streams, rivers, lakes, and other bodies of water. As the heated runoff enters these bodies of water, their temperatures rise.” (United States Environmental Protection Agency).

Park's Five Borough Administraitive Building Green Roof

Any Measures?

Most efforts to cool urban communities rely on reintroducing vegetation into the urban environment to mimic nature's own natural cooling, shading and reflective techniques. For example, some cities are adding more parks, green spaces, green roofs, tree-lined streets and urban farms to their developments. Communities are also increasingly adopting 'green' or ecological buildings and incorporating features such as green roofs into building design to reduce indoor and outdoor temperatures. Some cities are also reducing the impact of heat islands by increasing the reflectivity of existing urban surfaces. “For example, New York, the largest city in the USA, added a requirement for white roofs to its building code as early as 2008. (White surfaces reflect up to 90 percent of sunlight, while dark surfaces such as asphalt reflect about 5 percent.) Similarly, Los Angeles, the second largest city in the USA, introduced various "cool pavement" pilot projects, during which the city painted its traditional asphalt pavement light grey and white.” (7 ways to reduce the urban heat island effect)

In order to mitigate the urban heat island phenomenon, comprehensive and effective measures must be taken along with monitoring the urban thermal environment and analyzing the influencing factors and cost-effectiveness. The urban heat island phenomenon is profoundly linked to urbanization, which has been shaped by human history for a long time and therefore inevitably requires long-term planning. In order to implement a long-term plan, there is a case for progressively strengthening the response measures as the plan is flexibly revised. To this end, the latest scientific knowledge and technology should be reviewed as the UHI is monitored.

"THE THREE MAIN AREAS"

There are three main areas of response to UHI:

1 reducing anthropocentric heat emissions. In particular, a large number of motor vehicles, industrial production, and residential life often emit large amounts of pollutants such as nitrogen oxides, carbon dioxide, and dust. These substances not only absorb all kinds of heat radiation generated by the city but also create an invisible "glass envelope" in the atmosphere, which prevents some of the heat from escaping into outer space, creating a "greenhouse effect". This situation will eventually further accelerate the warming of the atmosphere。 With urbanization, there has been a massive influx of people into cities, leading to an increase in urban population density, which has also exacerbated the urban heat island effect.

2 improving the urban surface. The use of thermal insulation in building walls or the application of light paint to external walls and roof surfaces can improve the reflectivity of solar radiation. This reduces the absorption rate and thus mitigates the urban heat island effect.

3 improving the urban structure. However, the UHI phenomenon also reflects the lifestyles of residents. Therefore, improving lifestyles should be part of the solution. The understanding and support of residents have an important role to play in improving the phenomenon. (THE POLICY FRAMEWORK TO REDUCE URBAN HEAT ISLAND EFFECTS）

Explanation of the three main areas

1. Reduction of Anthropogenic Heat Emission

In order to reduce anthropogenic heat emission from such as air conditioning, electric equipment and automobiles, the following measures shall be carried out;

-Facilitation to improve the efficiency of energy-consuming equipments by subsidizing new technology development and installation of its outcome.

-Facilitation to diffuse high energy efficient houses and buildings by policy-based finance, model projects developing environment friendly houses and urban areas and utilization of "Energy Service Company (ESCO)"

-Facilitation of the technology development and the diffusion of low emission vehicles

-Traffic control measures, facilitation of rationalization of the distribution and encouraging use of public transportation

-Encouragement of the use of new energy

2. Improvement of Urban Surface

-In order to mitigate decrease of evapo-transpiration and the high-temperature rise of the ground, which were caused by reduction of green space and water and the expansion of impervious surface such as buildings and asphalt, the following measures for the improvement of the urban surface shall be carried out;

-Facilitation of tree-planting in private houses, buildings and their sites

-Promotion of tree planting in public facilities such as government buildings

-Construction of urban parks and promotion of tree-planting in public spaces such as ports, airports and sewage plants

3. Improvement of urban structure

In order to ensure wind flow through green spaces and water, following measures for the improvement of urban structure shall be carried out;

-Development of network with green and water in the region across the prefectures by construction of large green spaces and making up the linkage between parks, rivers, and roads 。

-Feasibility study on the urban heat emission treatment system which carries heat from the very densely build-up area to rivers and sea through underground pipes with circulating water。

--Facilitation to utilize of the city planning system to develop "less environmental burden cities"。（THE POLICY FRAMEWORK TO REDUCE URBAN HEAT ISLAND EFFECTS）

What needs to think about?

Energy planning and energy policies are very important in the development of the master planning phase of a city because of the large amount of heat generated by the use of fossil fuels in production and living. The rational development of a city's energy plan is an important part of the overall planning and design of the city. It is imperative that energy plans and energy policies are developed as soon as possible to replace fossil fuels such as oil with natural energy sources that do not have a negative impact on the environment and are recyclable (also known as green energy).

The UHI phenomenon varies according to its location. It is, therefore, necessary to implement measures in cooperation with local governments. the UHI phenomenon reflects a wide range of social and economic activities. Therefore, partnerships between governments, businesses, and residents are important in the implementation of measures. In addition, links with other environmental policies such as global warming, cities, transport, and energy should be promoted.

It is also worth considering the issue of area thresholds for urban green spaces. For example, in some cosmopolitan cities the total green space coverage has been increasing in recent decades, but at the same time the 'heat island' intensity has also been increasing, which may indicate that the rapid expansion of cities has significantly increased the intensity of the regional 'heat island', while the increase in green space has not been able to offset the increase in temperature caused by urban expansion. This may indicate that the rapid urban expansion has significantly increased the regional 'heat island' intensity, while the increase in green space has not been able to offset the increase in temperature caused by urban expansion. Therefore, in the formation of large cities and even urban agglomerations, it is important to pay attention to how green spaces are deployed and how high the green space coverage can effectively mitigate the 'heat island' intensity.

Works Cited

Dunbar, Brian. “Ecosystem, Vegetation Affect Intensity of Urban Heat Island Effect.” NASA, NASA, https://www.nasa.gov/mission_pages/terra/news/heat-islands.html.

About RinkeshA true environmentalist by heart ❤️. Founded Conserve Energy Future with the sole motto of providing helpful information related to our rapidly depleting environment. Unless you strongly believe in Elon Musk‘s idea of making Mars as another h , et al. “Causes, Effects and Solutions to Urban Heat Island.” Conserve Energy Future, 28 July 2022, https://www.conserve-energy-future.com/effects-solutions-urban-heat-island.php.

https://www.epa.gov/heatislands/heat-island-impacts

By Inter-Ministry Coordination Committee to mitigate urban ... - env.go.jp. (n.d.). Retrieved November 21, 2022, from https://www.env.go.jp/en/air/heat/heatisland.pdf

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