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 Surface Urban Heat Islands Dynamics in Response to LULC and Vegetation across South Asia (2000–2019)

2021 ◽  
Vol 13 (16) ◽  
pp. 3177
Author(s):  
Talha Hassan ◽  
Jiahua Zhang ◽  
Foyez Ahmed Prodhan ◽  
Til Prasad Pangali Sharma ◽  
Barjeece Bashir
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Areas ◽  
Vegetation Index ◽  
Thermal Environment ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Urban Heat

Urbanization is an increasing phenomenon around the world, causing many adverse effects in urban areas. Urban heat island is are of the most well-known phenomena. In the present study, surface urban heat islands (SUHI) were studied for seven megacities of the South Asian countries from 2000–2019. The urban thermal environment and relationship between land surface temperature (LST), land use landcover (LULC) and vegetation were examined. The connection was explored with remote-sensing indices such as urban thermal field variance (UTFVI), surface urban heat island intensity (SUHII) and normal difference vegetation index (NDVI). LULC maps are classified using a CART machine learning classifier, and an accuracy table was generated. The LULC change matrix shows that the vegetated areas of all the cities decreased with an increase in the urban areas during the 20 years. The average LST in the rural areas is increasing compared to the urban core, and the difference is in the range of 1–2 (°C). The SUHII linear trend is increasing in Delhi, Karachi, Kathmandu, and Thimphu, while decreasing in Colombo, Dhaka, and Kabul from 2000–2019. UTFVI has shown the poor ecological conditions in all urban buffers due to high LST and urban infrastructures. In addition, a strong negative correlation between LST and NDVI can be seen in a range of −0.1 to −0.6.

scholarly journals Mitigating the Urban Heat Island Effect in Megacity Tehran

2014 ◽  
Vol 2014 ◽  
pp. 1-19 ◽  
Author(s):  
Sahar Sodoudi ◽  
Parisa Shahmohamadi ◽  
Ken Vollack ◽  
Ulrich Cubasch ◽  
A. I. Che-Ani
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Heat Waves ◽  
Mitigation Strategies ◽  
Cooling Effect ◽  
Heat Island ◽  
Microscale Model ◽  
Negative Effect ◽  
Urban Heat ◽  
Surrounding Areas

Cities demonstrate higher nocturnal temperatures than surrounding rural areas, which is called “urban heat island” (UHI) effect. Climate change projections also indicate increase in the frequency and intensity of heat waves, which will intensify the UHI effect. As megacity Tehran is affected by severe heatwaves in summer, this study investigates its UHI characteristics and suggests some feasible mitigation strategies in order to reduce the air temperature and save energy. Temperature monitoring in Tehran shows clear evidence of the occurrence of the UHI effect, with a peak in July, where the urban area is circa 6 K warmer than the surrounding areas. The mobile measurements show a park cool island of 6-7 K in 2 central parks, which is also confirmed by satellite images. The effectiveness of three UHI mitigation strategies high albedo material (HAM), greenery on the surface and on the roofs (VEG), and a combination of them (HYBRID) has been studied using simulation with the microscale model ENVI-met. All three strategies show higher cooling effect in the daytime. The average nocturnal cooling effect of VEG and HYBRID (0.92, 1.10 K) is much higher than HAM (0.16 K), although high-density trees show a negative effect on nocturnal cooling.

Emergence of opposite trends in daytime and night-time urban heat island intensities in England

2020 ◽  
Author(s):  
Eunice Lo ◽  
Dann Mitchell ◽  
Sylvia Bohnenstengel ◽  
Mat Collins ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Urban Land Use ◽  
Urban Heat Islands ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Night Time ◽  
Heat Islands ◽  
Island Effect ◽  
Urban Heat

<p>Urban environments are known to be warmer than their sub-urban or rural surroundings, particularly at night. In summer, urban heat islands exacerbate the occurrence of extreme heat events, posing health risks to urban residents. In the UK where 90% of the population is projected to live in urban areas by 2050, projecting changes in urban heat islands in a warming climate is essential to adaptation and urban planning.</p><p>With the use of the new UK Climate Projections (UKCP18) in which urban land use is constant, I will show that both summer urban and sub-urban temperatures are projected to increase in the 10 most populous built-up areas in England between 1980 and 2080. However, differential warming rates in urban and sub-urban areas, and during day and at night suggest a trend towards a reduced daytime urban heat island effect but an enhanced night-time urban heat island effect. These changes in urban heat islands have implications on thermal comfort and local atmospheric circulations that impact the dispersion of air pollutants. I will further demonstrate that the opposite trends in daytime and night-time urban heat island effects are projected to emerge from current variability in more than half of the studied cities below a global mean warming of 3°C above pre-industrial levels.</p>

Evolutionary Consequences of the Urban Heat Island

2020 ◽  
pp. 91-110 ◽  
Author(s):  
Sarah E. Diamond ◽  
Ryan A. Martin
Keyword(s):  
Urban Heat Island ◽  
Urban Areas ◽  
Climatic Conditions ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Heat Islands ◽  
Physiological Tolerance ◽  
Downstream Effects ◽  
Urban Heat ◽  
Evolutionary Consequences

As humans continue to modify the climatic conditions organisms encounter, downstream effects on the phenotypes of organisms are likely to arise. In particular, the worldwide proliferation of human settlements rapidly generates pockets of localized warming across the landscape. These urban heat island effects are frequently intense, especially for moderate to larger sized cities, where urban centres can be several degrees Celsius warmer compared with nearby non-urban areas. Although organisms likely ameliorate the effects of warming through phenotypic plasticity, the evolution of thermally sensitive traits may be an important yet underappreciated means of survival. Recent work suggests the potential for contemporary evolutionary change in association with urban heat islands across a diverse suite of traits from morphology to physiological tolerance, growth rate, and metabolism. This chapter reviews and synthesizes this work. It first develops a comprehensive set of predictions for adaptive evolutionary changes in morphology, physiology, and life-history traits driven by urban heat islands. It then evaluates these predictions with regard to the burgeoning literature on urban evolution of thermally sensitive traits.

scholarly journals Urban Thermal Environment and Heat Island in Ho Chi Minh City, Vietnam from Remote Sensing Data

2017 ◽  
Author(s):  
Van Tran Thi ◽  
Bao Ha Duong Xuan ◽  
Mai Nguyen Thi Tuyet
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Rural Areas ◽  
Land Surface ◽  
Urban Areas ◽  
Ho Chi Minh City ◽  
Heat Island ◽  
Urban Heat ◽  
Surface Urban Heat Island ◽  
The Impact

In urban area, one of the great problem is the rise of temperature, which leads to form the urban heat island effect. This paper refers to the trend of the urban surface temperature extracted from the Landsat images from which to consider changes in the formation of surface urban heat island for the north of Ho Chi Minh city in period 1995-2015. Research has identified land surface temperature from thermal infrared band, according to the ability of the surface emission based on characteristics of normalized difference vegetation index NDVI. The results showed that temperature fluctuated over the city with a growing trend and the gradual expansion of the area of the high-temperature zone towards the suburbs. Within 20 years, the trend of the formation of surface urban heat island with two typical locations showed a clear difference between the surface temperature of urban areas and rural areas with space expansion of heat island in 4 times in 2015 compared to 1995. An extreme heat island located in the inner city has an area of approximately 18% compared to the total area of the region. Since then, the solution to reduce the impact of urban heat island has been proposed, in order to protect the urban environment and the lives of residents in Ho Chi Minh City becoming better

scholarly journals Comparative Analysis of Urban Heat Island Intensities in Chinese, Russian, and DPRK Regions across the Transnational Urban Agglomeration of the Tumen River in Northeast Asia

2018 ◽  
Vol 10 (8) ◽  
pp. 2637 ◽  
Author(s):  
Bing Li ◽  
Zhifeng Liu ◽  
Ying Nan ◽  
Shengnan Li ◽  
Yanmin Yang
Keyword(s):  
Urban Heat Island ◽  
Urban Agglomeration ◽  
Urban Heat Islands ◽  
City Size ◽  
Vegetation Coverage ◽  
Heat Island ◽  
Tumen River ◽  
Heat Islands ◽  
Urban Heat ◽  
The Impact

Quantification of the spatial pattern of urban heat island intensities across the transnational urban agglomeration of the Tumen River is important for the promotion of sustainable regional development. This study employed Landsat images and MODIS LST data obtained in 2016 to determine the intensity of urban heat islands in this region, enabling direct comparison of data from the sub-regions of China, Democratic People’s Republic of Korea (DPRK), and Russia. The average urban heat island intensity for the region was found to be 1.0 °C, with the highest intensity of 3.0 °C occurring during the summer time. The intensity of urban heat islands on the Chinese side was higher than on the other two sides, with city size, socio-economic development levels and vegetation coverage significantly affect their intensity. Urban heat island effects in Chinese cities in the region contribute increases in maximum summer temperatures and the number of high-temperature days that pose a threat to the health of their residents. The factors that influence urban heat island intensities in these cities and the impacts of urban heat island effects on the quality of life and health of residents are discussed. Therefore, it is desirable to reduce the impact of urban heat island effects on cities in the region by increasing the area of green spaces they contain, as well as controlling their size and population.

scholarly journals Characterization of the urban microclimate by the modelling of urban planning policies in France

2021 ◽  
Vol 2042 (1) ◽  
pp. 012065
Author(s):  
Magalie Técher ◽  
Hassan Ait Haddou ◽  
Rahim Aguejdad
Keyword(s):  
Urban Planning ◽  
Urban Heat Island ◽  
Urban Form ◽  
Urban Heat Islands ◽  
Heat Island ◽  
Urban Microclimate ◽  
Heat Islands ◽  
Urban Heat ◽  
The Impact ◽  
Planning Policies

Abstract With the increase of Urban Heat Islands (UHI) and the effects of global warming, cities will face challenges in anticipating these phenomena. However, the complexity of urban development within the framework of urban planning policies, makes difficult for urban decision-makers to anticipate the Urban Heat Islands within their territory. In this paper, we propose a methodology to assess the impact of urban planning policies on Urban Heat Island. Thanks to a coupling of 2D urban growth model, 3D constructability model and urban microclimate simulation, this tool will make it possible to visualize the impact of urban planning decisions on urban form and on Urban Heat Island.

scholarly journals Synergies between urban heat island and heat waves in Seoul: The role of wind speed and land use characteristics

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243571
Author(s):  
Jack Ngarambe ◽  
Jacques Nganyiyimana ◽  
Inhan Kim ◽  
Mat Santamouris ◽  
Geun Young Yun
Keyword(s):  
Land Use ◽  
Wind Speed ◽  
Urban Heat Island ◽  
Rural Areas ◽  
Urban Areas ◽  
Heat Waves ◽  
Weather Conditions ◽  
Heat Island ◽  
Emergency Relief ◽  
Urban Heat

The effects of heat waves (HW) are more pronounced in urban areas than in rural areas due to the additive effect of the urban heat island (UHI) phenomenon. However, the synergies between UHI and HW are still an open scientific question and have only been quantified for a few metropolitan cities. In the current study, we explore the synergies between UHI and HW in Seoul city. We consider summertime data from two non-consecutive years (i.e., 2012 and 2016) and ten automatic weather stations. Our results show that UHI is more intense during HW periods than non-heat wave (NHW) periods (i.e., normal summer background conditions), with a maximum UHI difference of 3.30°C and 4.50°C, between HW and NHW periods, in 2012 and 2016 respectively. Our results also show substantial variations in the synergies between UHI and HW due to land use characteristics and synoptic weather conditions; the synergies were relatively more intense in densely built areas and under low wind speed conditions. Our results contribute to our understanding of thermal risks posed by HW in urban areas and, subsequently, the health risks on urban populations. Moreover, they are of significant importance to emergency relief providers as a resource allocation guideline, for instance, regarding which areas and time of the day to prioritize during HW periods in Seoul.

scholarly journals Observational evidence of urban heat island intensification during heatwaves in European cities

2021 ◽  
Author(s):  
Marco Possega ◽  
Leonardo Aragão ◽  
Paolo Ruggieri ◽  
Marco Antonio Santo ◽  
Silvana Di Sabatino
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
Heat Waves ◽  
Observational Evidence ◽  
Extreme Heat ◽  
Mitigation Strategies ◽  
Daily Maximum ◽  
Heat Island ◽  
European Cities ◽  
Urban Heat

<p>Heat waves (HWs) are extreme weather conditions characterized by persistent high temperatures with considerable impacts on society in terms of<br>mortality, thermal stress and energy demand of the population. One of the most interesting aspects of HWs concerns the interaction with the phenomenon<br>of urban heat island (UHI). The UHI is the tendency of urbanized areas to have warmer temperatures than the surrounding rural areas, mainly due to the thermal<br>properties of materials forming urban environment and the heat produced by human activities. Some studies analyzed the behavior of UHI during periods of<br>extreme heat, showing an amplification of the gradient of temperature between urban and rural areas in HW conditions, but results are often limited to case<br>studies with a single HW and/or a specific city. Other papers dealt with the same topic by examining events on various cities using outputs of global models,<br>but with resolution insufficient to include in detail urban-scale processes and therefore to take into account specific properties of the cities investigated. The<br>approach of this work consisted in providing observational evidence and extending the aforementioned results, studying the effect of HWs on UHI in 41 European cities<br>with different characteristics (geography, topography, urban planning) through the analysis of daily maximum / minimum temperatures data measured by<br>meteorological stations for the summers of period 2000-2019. In particular, the intensity of UHI was assessed through the computation of a Composite UHI Index<br>(UHII), defined as the difference between averaged urban and non-urban values. The different behavior of UHII during HWs compared to "normal" summer days<br>(NO) in selected European cities was investigated, detecting an intensification of index values regarding periods of extreme heat for the majority of examined<br>locations. More specifically, the analysis of temporal evolution of UHII was conducted, revealing an average increase of this index during the occurrence of<br>HW events due to higher urban than rural temperatures. This work provides an indication of how European urban areas respond to severe hot periods and could<br>be useful to validate numerical model simulations for more detailed analysis, for example regarding mitigation strategies. Finally, the emergence of some outliers,<br>namely cities whose UHI manifested a different reaction to HWs, may deserve dedicated studies in the future.</p><p> </p>

scholarly journals The mechanisms and seasonal differences of the impact of aerosols on daytime surface urban heat island effect

2020 ◽  
Vol 20 (11) ◽  
pp. 6479-6493 ◽  
Author(s):  
Wenchao Han ◽  
Zhanqing Li ◽  
Fang Wu ◽  
Yuwei Zhang ◽  
Jianping Guo ◽  
...  
Keyword(s):  
Air Pollution ◽  
Urban Heat Island ◽  
Rural Areas ◽  
Urban Areas ◽  
Urban Climate ◽  
Dynamic Effect ◽  
Heat Island ◽  
Near Surface ◽  
Urban Heat ◽  
The Impact

Abstract. The urban heat island intensity (UHII) is the temperature difference between urban areas and their rural surroundings. It is commonly attributed to changes in the underlying surface structure caused by urbanization. Air pollution caused by aerosol particles can affect the UHII through changing (1) the surface energy balance by the aerosol radiative effect (ARE) and (2) planetary-boundary-layer (PBL) stability and airflow intensity by modifying thermodynamic structure, which is referred to as the aerosol dynamic effect (ADE). By analyzing satellite data and ground-based observations collected from 2001 to 2010 at 35 cities in China and using the WRF-Chem model, we find that the impact of aerosols on UHII differs considerably: reducing the UHII in summer but increasing the UHII in winter. This seasonal contrast is proposed to be caused by the different strengths of the ARE and ADE between summer and winter. In summer, the ARE on UHII is dominant over the ADE, cooling down surface temperature more strongly in urban areas than in rural areas because of much higher aerosol loading, and offsets the urban heating, therefore weakening UHII. In winter, however, the ADE is more dominant, because aerosols stabilize the PBL more in the polluted condition, weakening the near-surface heat transport over urban areas in both vertical and horizontal directions. This means that the heat accumulated in urban areas is dispersed less effectively, and thus the UHII is enhanced. These findings shed new light on the impact of the interaction between urbanization-induced surface changes and air pollution on urban climate.

Sign in / Sign up

Export Citation Format

Share Document