User:Merlinderhindergrinder/sandbox

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You will use your own sandbox page to create an annotated bibliography of reliable sources that will help you make a substantive contribution to your article.

You will also use a sandbox page to draft the changes that your group with publish to your article.

This is a WYSIWYG editor,

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Evaluate an article: Urban Heat Island

In general, high-quality articles have five elements:

• A lead section that gives an easy-to-understand overview

I think the lead is too long. It touches on some of the main issues around urban heat islands, but I don't know if introducing those issues briefly in the lead is the best way to go about it - they could be introduced and further developed in their own sections in the article, and those sections do already exist. There are also a few unsourced claims in the lead.

• A clear structure

Definition section contains citations that should be cleaned up to more clearly communicate what publication is being cited.

The Diurnal variability section could be written more clearly - it is a little jargon-y.

There are some potentially contradictory claims in the Green Infrastructure section that could be rewritten and reorganized to be more clear.

I am wondering if the section on redlining should be moved into the section on Aspects of social inequality.

• Balanced coverage

It is true that the examples section is US-centric. There are other international examples mentioned at earlier points in the article that I could follow up on to provide other examples.

• Neutral content

Climate change as an amplifier but not a cause of UHIs seems like it's worth discussing. There is something kind of hedgey or semi-denialist about the tone and I am hoping to rewrite this section be clear, factual, and encyclopedic in tone.

• Reliable sources

There is likely more evidence available for the Redlining section.

There are two citation needed tags in the Seasonal variability section.

The section On energy usage for cooling should have an updated source for the LA data (it's more than 20 years old). All of the sources in that section are pretty old, and surely there is more recent data available about air conditioning.

There are two citation needed tags in the Green infrastructure section.

The Sydney section has a needs sources header.


 * Move Causes and Climate Change as Amplifier under Description
 * Move Redlining under society and culture
 * Consider creating Environmental Justice section
 * Revise lead to shorten and clarify

Causes
[edit] See also: Heatwave § Formation

There are several causes of an urban heat island (UHI); for example, dark surfaces absorb significantly more solar radiation, which causes urban concentrations of roads and buildings to heat more than suburban and rural areas during the day; materials commonly used in urban areas for pavement and roofs, such as concrete and asphalt, have significantly different thermal bulk properties (including heat capacity and thermal conductivity) and surface radiative properties (albedo and emissivity) than the surrounding rural areas. This causes a change in the energy budget of the urban area, often leading to higher temperatures than surrounding rural areas.

Pavements, parking lots, roads or, more generally speaking transport infrastructure, contribute significantly to the urban heat island effect. For example, pavement infrastructure is a main contributor to urban heat during summer afternoons in Phoenix, Arizona, United States.

Another major reason is the lack of evapotranspiration (for example, through lack of vegetation) in urban areas. The U.S. Forest Service found in 2018 that cities in the United States are losing 36 million trees each year. With a decreased amount of vegetation, cities also lose the shade and evaporative cooling effect of trees.

Other causes of a UHI are due to geometric effects. The tall buildings within many urban areas provide multiple surfaces for the reflection and absorption of sunlight, increasing the efficiency with which urban areas are heated. This is called the "urban canyon effect". Another effect of buildings is the blocking of wind, which also inhibits cooling by convection and prevents pollutants from dissipating. Waste heat from automobiles, air conditioning, industry, and other sources also contributes to the UHI.

High levels of pollution in urban areas can also increase the UHI, as many forms of pollution change the radiative properties of the atmosphere. UHI not only raises urban temperatures but also increases ozone concentrations because ozone is a greenhouse gas whose formation will accelerate with the increase of temperature.

Climate change as an amplifier
[edit] Further information: Climate change and cities and Climate change adaptation § Heatwaves

Climate change amplifies the urban heat island effect. The IPCC Sixth Assessment Report from 2022 summarized the available research accordingly: "Climate change increases heat stress risks in cities [...] and amplifies the urban heat island across Asian cities at 1.5°C and 2°C warming levels, both substantially larger than under present climates [...]."

The report goes on to say: "In a warming world, increasing air temperature makes the urban heat island effect in cities worse. One key risk is heatwaves in cities that are likely to affect half of the future global urban population, with negative impacts on human health and economic productivity."

There are unhelpful interactions between heat and built infrastructure: These interactions increase the risk of heat stress for people living in cities.

Diurnal variability
[edit]

Throughout the daytime, particularly when the skies are cloudless, urban surfaces are warmed by the absorption of solar radiation. Surfaces in the urban areas tend to warm faster than those of the surrounding rural areas. By virtue of their high heat capacities, urban surfaces act as a reservoir of heat energy. For example, concrete can hold roughly 2,000 times as much heat as an equivalent volume of air. As a result, high daytime surface temperatures within the UHI can be easily seen via thermal remote sensing. As is often the case with daytime heating, this warming also has the effect of generating convective winds within the urban boundary layer. At night, the situation reverses. The absence of solar heating leads to the decrease of atmospheric convection and the stabilization of urban boundary layer. If enough stabilization occurs, an inversion layer is formed. This traps urban air near the surface, and keeping surface air warm from the still-warm urban surfaces, resulting in warmer nighttime air temperatures within the UHI.

Generally speaking, the difference in temperature between the urban and surrounding rural area is more pronounced at night that in daytime. For example, in the United States, the temperature in urban areas tends to be warmer than the surrounding area 1-7° F during the daytime, and about 2-5° F warmer at night. However, the difference is more pronounced during the day in arid climates such as those in southeastern China and Taiwan. Studies have shown that diurnal variability is impacted by several factors including local climate and weather, seasonality, humidity, vegetation, surfaces, and materials in the built environment.

Other than the heat retention properties of urban areas, the nighttime maximum in urban canyons could also be due to the blocking of "sky view" during cooling: surfaces lose heat at night principally by radiation to the comparatively cool sky, and this is blocked by the buildings in an urban area. Radiative cooling is more dominant when wind speed is low and the sky is cloudless, and indeed the UHI is found to be largest at night in these conditions.

It is theorized that, due to the atmospheric mixing that results, the air temperature perturbation within the UHI is generally minimal or nonexistent during the day, though the surface temperatures can reach extremely high levels.

For most cities, the difference in temperature between the urban and surrounding rural area is largest at night. While temperature difference is significant all year round, the difference is generally bigger in winter. The typical temperature difference is several degrees between the city and surrounding areas. The difference in temperature between an inner city and its surrounding suburbs is frequently mentioned in weather reports, as in "68 °F (20 °C) downtown, 64 °F (18 °C) in the suburbs". In the United States, the difference during the day is between 0.6–3.9 °C The difference is larger for bigger cities and areas with a high air humidity.

Though the warmer air temperature within the UHI is generally most apparent at night, urban heat islands exhibit significant and somewhat paradoxical diurnal behavior. The air temperature difference between the UHI and the surrounding environment is large at night and small during the day.

Seasonal variability
[edit] Seasonal variability is less well understood than diurnal variability of the urban heat island temperature difference. . Complex relationships between precipitation, vegetation, solar radiation, and surface materials in various microclimates play interlocking roles that influence seasonal patterns of temperature variation in a particular urban heat island.

This is especially true in areas where snow is common, as cities tend to hold snow for shorter periods of time than surrounding rural areas (this is due to the higher insulation capacity of cities, as well as human activities such as plowing). This decreases the albedo of the city and thereby magnifies the heating effect. Higher wind speeds in rural areas, particularly in winter, can also function to make them cooler than urban areas. Regions with distinct wet and dry seasons will exhibit a larger urban heat island effect during the dry season.[citation needed

Green Roof

Green roofs (roofs with vegetation such as trees or a garden) may increase the albedo and decrease the urban heat island effect. Green roofs can also have positive impacts on stormwater management, air quality, and energy consumption. Cost can be a barrier to implementing a green roof. Several factors that influence the initial cost of a green roof, including design and soil depth, location, and the price of labor and equipment in that market, with costs typically lower in more developed markets where there is more experience designing and installing green roofs. The individualized context of each green roof presents a challenge for making broad comparisons and assessments, and focusing only on monetary costs may leave out the social, environmental, and public health benefits green roofs provide. Global comparisons of green roof performance are further challenged by the lack of a shared framework for making such comparisons.

Green roofery is the practice of having vegetation on a roof; such as having trees or a garden. The plants that are on the roof and decreases the urban heat island effect.

This method has been studied and criticized for the fact that green roofs are affected by climatic conditions, green roof variables are hard to measure, and are very complex systems.

The cost efficiency of green roofs is quite high because of several reasons.[citation needed] For one, green roofs have over double the lifespan of a conventional roof, effectively decelerating the amount of roof replacements every year. In addition to roof-life, green roofs add stormwater management reducing fees for utilities. The cost for green roofs is more in the beginning, but over a period of time, their efficiency provides financial as well as health benefits. However, "A conventional roof is estimated to be $83.78/m2 while a green roof was estimated at $158.82/m2."[92][clarification needed]

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