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>

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 ◽  
Observational Evidence ◽  
Extreme Heat ◽  
Mitigation Strategies ◽  
Maximum Temperature ◽  
Daily Maximum ◽  
Heat Island ◽  
European Cities ◽  
Urban Heat

<p>Heatwaves (HWs) are extreme weather conditions characterized by persistent high temperatures with considerable impacts on society in terms of mortality, thermal stress and energy demand of the population. One of the most interesting aspects of HWs concerns the interaction with the phenomenon 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 properties of materials forming urban environment and the heat produced by human activities. Some studies analyzed the behavior of UHI during periods of extreme heat, showing an amplification of the gradient of temperature between urban and rural areas in HW conditions, but the results are often limited to case 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, but with resolution insufficient to include in detail urban-scale processes and therefore to take into account specific properties of the cities investigated. The approach of this work consisted in providing observational evidence and extending the aforementioned results, studying the effect of HWs on UHI in about ten European cities with different characteristics (geography, topography, urban planning) through the analysis of daily maximum/minimum temperatures data measured by meteorological stations for the summers of period 2006-2019. In particular, the intensity of UHI was assessed through the computation of a Composite UHI Index (UHII), defined as the difference between averaged urban and non-urban values. The different behavior of UHII during HWs compared to "normal" summer days (NO) in selected European cities was investigated, detecting an intensification of index values regarding periods of extreme heat for the majority of examined locations. More specifically, the analysis of temporal evolution of UHII was conducted, revealing an average increase of this index during the occurrence of HW events. Moreover, a correlation between UHI index and maximum temperature anomalies was examined, and HW days appeared to exhibit a larger percentage of positive UHII with respect to NO days, showing also higher absolute values. This work provides an indication of how European urban areas respond to severe hot periods and could be useful to validate numerical model simulations for more detailed analysis, for example regarding mitigation strategies. Finally, the emergence of some outliers, namely cities whose UHI manifested a different reaction to HWs, may deserve dedicated studies in the future.</p>

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.

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 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 The Influence of Urban Climate on Bioclimatic Conditions in the City of Iași, Romania

2020 ◽  
Vol 12 (22) ◽  
pp. 9652
Author(s):  
Pavel Ichim ◽  
Lucian Sfîcă
Keyword(s):  
Inner City ◽  
Urban Heat Island ◽  
Rural Area ◽  
Rural Areas ◽  
Heat Waves ◽  
Urban Climate ◽  
Heat Island ◽  
Urban Heat ◽  
Bioclimatic Conditions ◽  
The City

This study was carried out in order to outline the human bioclimatic stress/comfort conditions within the area of Iași city, Romania. The meteorological data were obtained over a 7-year period (December 2012–November 2019) from an observation network relying on 8 fixed observation points located in selected spots, relevant for the urban climate conditions in the region. The results demonstrate firstly that throughout the entire analyzed period, using the thermo-hygrometric index (THI), “very cold” conditions characterize 4% of the entire year in the inner parts of the city and 6% in the rural area, while the “hot” THI conditions vary from 18% in the middle of the urban heat island to 15% in the rural area. Overall, the rural areas are generally more comfortable than the inner city, especially during summer, when the urban heat island (UHI) core is starting to develop from the evening and persists during the night. On the contrary, the UHI renders the inner city more comfortable than the rural surroundings from October to April. Similar bioclimatic conditions are also presented in detail for the summer by the relative strain index (RSI), which exceeds the stress threshold value mostly during heat waves, when a significant contrast between urban and rural areas is felt. In brief, it has been determined that the most suitable area for human comfort in Iași city is inside the urban area during the winter and in the rural areas during the summer.

scholarly journals The Impact of the Urban Heat Island during an Intense Heat Wave in Oklahoma City

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
Jeffrey B. Basara ◽  
Heather G. Basara ◽  
Bradley G. Illston ◽  
Kenneth C. Crawford
Keyword(s):  
Urban Heat Island ◽  
Heat Wave ◽  
Rural Areas ◽  
Oklahoma City ◽  
Apparent Temperature ◽  
Heat Island ◽  
Atmospheric Conditions ◽  
Urban Heat ◽  
The Impact ◽  
Intense Heat

During late July and early August 2008, an intense heat wave occurred in Oklahoma City. To quantify the impact of the urban heat island (UHI) in Oklahoma City on observed and apparent temperature conditions during the heat wave event, this study used observations from 46 locations in and around Oklahoma City. The methodology utilized composite values of atmospheric conditions for three primary categories defined by population and general land use: rural, suburban, and urban. The results of the analyses demonstrated that a consistent UHI existed during the study period whereby the composite temperature values within the urban core were approximately C warmer during the day than the rural areas and over C warmer at night. Further, when the warmer temperatures were combined with ambient humidity conditions, the composite values consistently revealed even warmer heat-related variables within the urban environment as compared with the rural zone.

A comparative study of urban heat island effects in two Belarusian cities from satellite and ground-based observations

2021 ◽  
Author(s):  
Heorhi Burchanka ◽  
Yahor Prakopchyk ◽  
Tsimafei Schlender ◽  
Aleh Baravik ◽  
Siarhei Barodka
Keyword(s):  
Urban Heat Island ◽  
Rural Areas ◽  
City Planning ◽  
Thermal Characteristics ◽  
Data Availability ◽  
Eastern Bloc ◽  
Temperature Fields ◽  
Landsat 8 ◽  
Heat Island ◽  
Urban Heat

<p>This study is devoted to analysis of urban development effects on surface thermal characteristics for the case of Belarusian cities of Minsk and Mahiloŭ. Both cities being situated on the same latitude (53.90 N) and not far from each other (~180 km distance), while also sharing a number of similar features typical for cities in Belarus (and in some other former Eastern Bloc countries as well), Minsk and Mahiloŭ nevertheless differ significantly in terms of their population, size and structure. It is therefore of interest to perform urban climate studies for these two cities in parallel.</p><p>First, we use geoinformation systems (QGIS), centralized city planning databases and Open Street Maps (OSM) vector data to implement description of Minsk and Mahiloŭ urban territories in terms of functional zones, taking into account such features as buildings density and urban area category (industrial, residential, business, recreational and other types).</p><p>Furthermore, we perform analysis of surface temperature fields for both cities from satellite data (Landsat-8) and ground-based observations, the latter including both regular meteorological stations (in urban as well as surrounding rural areas) and a volunteer network of weather and air quality sensors distributed in both cities as part of the AirMQ project [1]. We analyze observations for several months in the 2019-2021 period (depending on data availability), paying special attention to days with specific weather conditions (e.g. blocking anticyclones).</p><p>Analysis demonstrates clear evidence of significant urban heat island effects in thermal regimes of both cities, with specific areas of increased temperature related to urban zoning, industrial and green areas, buildings heights and density. However, the selected method of surface urban heat island (SUHI) detection turns out to be somewhat limited for the purposes of studying the effects of blocking anticyclones on urban heat island phenomena development, thereby calling for application of atmospheric numerical modelling techniques.</p><p>[1] AirMQ project, URL: https://airmq.by/</p>

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