scholarly journals Enhanced surface urban heat islands due to divergent urban-rural greening trends

2021 ◽  
Author(s):  
Chi Chen ◽  
Dan Li ◽  
Trevor F. Keenan
Keyword(s):  
Rural Areas ◽  
Urban Heat Islands ◽  
Anthropogenic Heat ◽  
Rapid Urbanization ◽  
Area Index ◽  
Heat Islands ◽  
Urban Rural ◽  
Urban Heat ◽  
Urban And Rural Areas ◽  
The Impact

Abstract Satellite observations show that the surface urban heat island intensity (SUHII) has been increasing over the last two decades. This is often accompanied by an increased urban-rural contrast of vegetation greenness. However, the contribution of uneven vegetation trends in urban and rural areas to the trend of SUHII is unclear, due to the confounding effects of climate change and changes in man-made amenities and anthropogenic heat sources. Here we use a data-model fusion approach to quantify such contributions during the peak growing season. We show that the LAIdif (the urban-rural difference of leaf area index) is increasing (P<0.05) in 189 of the selected 228 global megacities. The increasing trend of LAIdif from 2000 to 2019 accounts for about one quarter of the trend in satellite-derived SUHII, and the impact is particularly evident in places with rapid urbanization and rural cropland intensification. The marginal sensitivity of SUHII to LAIdif is the strongest in hot-humid megacities surrounded by croplands and in hot-dry megacities surrounded by mixed woody and herbaceous vegetation. Our study highlights the role of long-term vegetation trends in modulating the trends of urban-rural temperature differences.

scholarly journals Urban heat island: Aerodynamics or imperviousness?

2019 ◽  
Vol 5 (4) ◽  
pp. eaau4299 ◽  
Author(s):  
Dan Li ◽  
Weilin Liao ◽  
Angela J. Rigden ◽  
Xiaoping Liu ◽  
Dagang Wang ◽  
...  
Keyword(s):  
Green Infrastructure ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Heat Islands ◽  
Lower Atmosphere ◽  
Geographic Variations ◽  
Heat Islands ◽  
Urban Heat ◽  
The Difference ◽  
Urban And Rural Areas

More than half of the world’s population now live in cities, which are known to be heat islands. While daytime urban heat islands (UHIs) are traditionally thought to be the consequence of less evaporative cooling in cities, recent work sparks new debate, showing that geographic variations of daytime UHI intensity were largely explained by variations in the efficiency with which urban and rural areas convect heat from the land surface to the lower atmosphere. Here, we reconcile this debate by demonstrating that the difference between the recent finding and the traditional paradigm can be explained by the difference in the attribution methods. Using a new attribution method, we find that spatial variations of daytime UHI intensity are more controlled by variations in the capacity of urban and rural areas to evaporate water, suggesting that strategies enhancing the evaporation capability such as green infrastructure are effective ways to mitigate urban heat.

Synergistic Interactions between Urban Heat Islands and Heat Waves: The Impact in Cities Is Larger than the Sum of Its Parts

2013 ◽  
Vol 52 (9) ◽  
pp. 2051-2064 ◽  
Author(s):  
Dan Li ◽  
Elie Bou-Zeid
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Urban Areas ◽  
Heat Waves ◽  
Mitigation Strategies ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Urban Heat ◽  
The Impact

AbstractCities are well known to be hotter than the rural areas that surround them; this phenomenon is called the urban heat island. Heat waves are excessively hot periods during which the air temperatures of both urban and rural areas increase significantly. However, whether urban and rural temperatures respond in the same way to heat waves remains a critical unanswered question. In this study, a combination of observational and modeling analyses indicates synergies between urban heat islands and heat waves. That is, not only do heat waves increase the ambient temperatures, but they also intensify the difference between urban and rural temperatures. As a result, the added heat stress in cities will be even higher than the sum of the background urban heat island effect and the heat wave effect. Results presented here also attribute this added impact of heat waves on urban areas to the lack of surface moisture in urban areas and the low wind speed associated with heat waves. Given that heat waves are projected to become more frequent and that urban populations are substantially increasing, these findings underline the serious heat-related health risks facing urban residents in the twenty-first century. Adaptation and mitigation strategies will require joint efforts to reinvent the city, allowing for more green spaces and lesser disruption of the natural water cycle.

scholarly journals Urban Heat Islands and Their Associated Impacts on Health

2020 ◽  
Author(s):  
Clare Heaviside
Keyword(s):  
Rural Areas ◽  
Heat Exposure ◽  
Urban Heat Islands ◽  
Heat Islands ◽  
Weather Patterns ◽  
Local Air Pollution ◽  
Urban Heat ◽  
The Difference ◽  
The Right ◽  
The Impact

Towns and cities generally exhibit higher temperatures than rural areas for a number of reasons, including the effect that urban materials have on the natural balance of incoming and outgoing energy at the surface level, the shape and geometry of buildings, and the impact of anthropogenic heating. This localized heating means that towns and cities are often described as urban heat islands (UHIs). Urbanized areas modify local temperatures, but also other meteorological variables such as wind speed and direction and rainfall patterns. The magnitude of the UHI for a given town or city tends to scale with the size of population, although smaller towns of just thousands of inhabitants can have an appreciable UHI effect. The UHI “intensity” (the difference in temperature between a city center and a rural reference point outside the city) is on the order of a few degrees Celsius on average, but can peak at as much as 10°C in larger cities, given the right conditions. UHIs tend to be enhanced during heatwaves, when there is lots of sunshine and a lack of wind to provide ventilation and disperse the warm air. The UHI is most pronounced at night, when rural areas tend to be cooler than cities and urban materials radiate the energy they have stored during the day into the local atmosphere. As well as affecting local weather patterns and interacting with local air pollution, the UHI can directly affect health through heat exposure, which can exacerbate minor illnesses, affect occupational performance, or increase the risk of hospitalization and even death. Urban populations can face serious risks to health during heatwaves whereby the heat associated with the UHI contributes additional warming. Heat-related health risks are likely to increase in future against a background of climate change and increasing urbanization throughout much of the world. However, there are ways to reduce urban temperatures and avoid some of the health impacts of the UHI through behavioral changes, modification of buildings, or by urban scale interventions. It is important to understand the physical properties of the UHI and its impact on health to evaluate the potential for interventions to reduce heat-related impacts.

scholarly journals Green roofs and cool materials as retrofitting strategies for urban heat island mitigation: Case study in Belgrade, Serbia

2018 ◽  
Vol 22 (6 Part A) ◽  
pp. 2309-2324
Author(s):  
Marija Lalosevic ◽  
Mirko Komatina ◽  
Marko Milos ◽  
Nedzad Rudonja
Keyword(s):  
Green Roofs ◽  
Urban Heat Islands ◽  
Temperature Changes ◽  
Heat Islands ◽  
Air Temperatures ◽  
Urban Heat ◽  
Microclimatic Conditions ◽  
Typical Summer ◽  
Planning And Construction ◽  
The Impact

The effect of extensive and intensive green roofs on improving outdoor microclimate parameters of urban built environments is currently a worldwide focus of research. Due to the lack of reliable data for Belgrade, the impact of extensive and intensive green roof systems on mitigating the effects of urban heat islands and improving microclimatic conditions by utilizing high albedo materials in public spaces were studied. Research was conducted on four chosen urban units within existing residential blocks in the city that were representative of typical urban planning and construction within the Belgrade metropolitan area. Five different models (baseline model and four potential models of retrofitting) were designed, for which the temperature changes at pedestrian and roof levels at 07:00, 13:00, 19:00 h, on a typical summer day, and at 01:00 h, the following night in Belgrade were investigated. The ENVI-met software was used to model the simulations. The results of numerical modeling showed that utilizing green roofs in the Belgrade climatic area could reduce air temperatures in the surroundings up to 0.47, 1.51, 1.60, 1.80 ?C at pedestrian level and up to 0.53, 1.45, 0.90, 1.45 ?C at roof level for four potential retrofitting strategies, respectively.

scholarly journals A Quantitative Assessment of Surface Urban Heat Islands Using Satellite Multitemporal Data over Abeokuta, Nigeria

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
K. A. Ishola ◽  
E. C. Okogbue ◽  
O. E. Adeyeri
Keyword(s):  
Land Cover ◽  
Urban Expansion ◽  
Regional Scale ◽  
Thermal Response ◽  
Urban Heat Islands ◽  
Rapid Urbanization ◽  
Land Cover Types ◽  
Remarkable Effect ◽  
Heat Islands ◽  
Urban Heat

The fast urban expansion has led to the transformation of the natural landscape into anthropogenic surfaces. The city of Abeokuta, for instance, is located in a region experiencing rapid urbanization, which has produced a remarkable effect on the surface thermal response. This effect significantly influences urban internal microclimatology on a regional scale. In this study, the surface temperatures and land cover types retrieved from Landsat TM and ETM+ images of Abeokuta city for 1984, 2003, and 2014 were analyzed. A quantitative approach was used to assess surface urban heat islands through the relationships among surface temperature and land cover types. Results showed that impervious surface areas were found to be correlated positively with high temperatures. Conversely, vegetated areas and bare surfaces correlated positively with mid temperature zones. This study found that areas with increasing impervious surfaces will accelerate LST rise and consequently lead to increasing effect of surface urban heat islands. These findings pose a major challenge to urban planners. However, the study would help to quantify the impacts of different scenarios (e.g., vegetation loss to accommodate urban growth) on LST and consequently to devise appropriate policy measures.

THE IMPACT OF URBANIZATION ON MURDER RATES AND ON THE GEOGRAPHY OF HOMICIDE IN ENGLAND AND WALES, 1780–1850

2010 ◽  
Vol 53 (3) ◽  
pp. 671-698 ◽  
Author(s):  
PETER KING
Keyword(s):  
Rural Areas ◽  
Rapid Urbanization ◽  
Homicide Rates ◽  
England And Wales ◽  
Large Cities ◽  
Methodological Problems ◽  
Urban And Rural Areas ◽  
And Migration ◽  
Impact Of Urbanization ◽  
The Impact

ABSTRACTAlthough higher murder rates have traditionally been associated with large cities, this view has recently been challenged by several historians who have argued that ‘homicide rates were negatively correlated with urbanisation and industrialisation’, and this is rapidly becoming the new consensus. By exploring the geography of homicide rates for one area undergoing rapid urbanization and industrialization – England and Wales, 1780–1850 – this article challenges this new view and re-assesses the relationship between recorded homicide rates and both modernization and urbanization. After discussing the methodological problems involved in using homicide statistics, it focuses mainly on the first fifteen years for which detailed county-based data is available – 1834–48 – as well as looking at the more limited late eighteenth-century and early nineteenth-century evidence. This data raises fundamental questions about the links historians have recently made between urbanization and low homicide rates, since the remote rural parts of England and Wales generally had very low recorded murder rates while industrializing and rapidly urbanizing areas such as Lancashire had very high ones. Potential explanations for these systematic and large variations between urban and rural areas – including the impact of age structures and migration patterns – are then explored.

scholarly journals The Influence of Vegetation on UHIs, MUHIs, and Microclimate of Selected Southern Cities

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 509A-509
Author(s):  
Derald A. Harp ◽  
Edward L. McWilliams
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Building Materials ◽  
Urban Heat Islands ◽  
Shopping Malls ◽  
Heat Islands ◽  
Suburban Areas ◽  
Winter Temperatures ◽  
Urban Heat ◽  
The City

Urban areas have average annual temperatures 2–3°C warmer than surrounding rural areas, with daily differences of 5–6°C common. A suggested reason for this temperature difference is the extensive use of concrete, asphalt, and other building materials in the urban environment. Vegetation can moderate these temperatures by intercepting incoming radiation. The influence of vegetation patterns on the magnitude of urban and micro-urban “heat islands” (UHI and MUHI, respectively) is compared for several cities including Houston, Austin, College Station, and Ft. Worth, Texas; Huntsville, Ala.; and Gainesville, Fla. Temperatures for all cities studied were greatest in the built-up areas and dropped off in suburban areas and adjacent rural areas. In Houston, surrounding rice fields were 3–5°C cooler than urban areas. Heavily built-up areas of Austin were 2–4°C warmer than parks and fields outside of the city. In all of the cities, large parks were typically 2–3°C cooler than adjacent built-up areas. Large shopping malls varied in nocturnal winter and summer temperature, with winter temperatures near door openings 2–3°C warmer, and summer daytime temperatures as much as 17°C cooler beneath trees. This effect seemed to persist at the microclimatic scale. Areas beneath evergreen trees and shrubs were warmer in the winter than surrounding grass covered areas. Video thermography indicated that the lower surfaces of limbs in deciduous trees were warmer than the upper surfaces. Overall, vegetation played a significant role, both at the local and microscale, in temperature moderation.

scholarly journals Urban Heat Island and Its Interaction with Heatwaves: A Review of Studies on Mesoscale

2021 ◽  
Vol 13 (19) ◽  
pp. 10923
Author(s):  
Jing Kong ◽  
Yongling Zhao ◽  
Jan Carmeliet ◽  
Chengwang Lei
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Anthropogenic Activities ◽  
Urban Heat Islands ◽  
Mitigation Measures ◽  
Rapid Urbanization ◽  
Pollution Dispersion ◽  
Vegetation Fraction ◽  
Holistic Review ◽  
Urban Heat

With rapid urbanization, population growth and anthropogenic activities, an increasing number of major cities across the globe are facing severe urban heat islands (UHI). UHI can cause complex impacts on the urban environment and human health, and it may bring more severe effects under heatwave (HW) conditions. In this paper, a holistic review is conducted to articulate the findings of the synergies between UHI and HW and corresponding mitigation measures proposed by the research community. It is worth pointing out that most studies show that urban areas are more vulnerable than rural areas during HWs, but the opposite is also observed in some studies. Changes in urban energy budget and major drivers are discussed and compared to explain such discrepancies. Recent studies also indicate that increasing albedo, vegetation fraction and irrigation can lower the urban temperature during HWs. Research gaps in this topic necessitate more studies concerning vulnerable cities in developing countries. Moreover, multidisciplinary studies considering factors such as UHI, HW, human comfort, pollution dispersion and the efficacy of mitigation measures should be conducted to provide more accurate and explicit guidance to urban planners and policymakers.

scholarly journals Resilience Thinking as a System Approach to Promote China’s Sustainability Transitions

2020 ◽  
Vol 12 (12) ◽  
pp. 5008
Author(s):  
Qirui Li
Keyword(s):  
Rural Areas ◽  
Mobility Control ◽  
Sustainability Transitions ◽  
Population Mobility ◽  
Policy Reforms ◽  
Rapid Urbanization ◽  
Resilience Thinking ◽  
Urban Rural ◽  
History Of ◽  
Urban And Rural Areas

Urban regeneration and rural revitalization are becoming major policy initiatives in China, which requires new approaches for sustainability transitions. This paper reviewed the history of policy reforms and institutional changes and analysed the main challenges to sustainability transitions in China. The urban-rural systems were defined as a complex dynamic social-ecological system based on resilience thinking and transition theory. The notions of adaptation and transformation were applied to compose a framework to coordinate “resilience” with “sustainability”. The findings indicate that China’s urbanization has experienced the conservative development of restructuring socio-economic and political systems (before 1984), the fast industrialization and economic development leaned to cities (1984 to 2002), the rapid urbanization led by land expropriation and investment expansion (2002 to 2012), and the quality development transformation equally in urban and rural areas (since 2012). The sustainability transitions have been challenged by controversial institutional arrangements, concerning population mobility control, unequal social welfare, and incomplete property rights. A series of policy interventions should be designed and implemented accordingly with joint efforts of multiple stakeholders and based on the combined technocratic and bottom-up knowledge derived from proactive and conscious individuals and collectives through context-dependent social networks.

Sign in / Sign up

Export Citation Format

Share Document