scholarly journals A New Method to Assess Fine-Scale Outdoor Thermal Comfort for Urban Agglomerations

Climate ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 6
Author(s):  
Dirk Lauwaet ◽  
Bino Maiheu ◽  
Koen De Ridder ◽  
Wesley Boënne ◽  
Hans Hooyberghs ◽  
...  
Keyword(s):  
Heat Stress ◽  
Thermal Comfort ◽  
Rural Areas ◽  
Urban Areas ◽  
Urban Heat Islands ◽  
Outdoor Thermal Comfort ◽  
Urban Agglomerations ◽  
Human Thermal Comfort ◽  
Air Temperatures ◽  
Water Surfaces

In urban areas, high air temperatures and heat stress levels greatly affect human thermal comfort and public health, with climate change further increasing the mortality risks. This study presents a high resolution (100 m) modelling method, including detailed offline radiation calculations, that is able to efficiently calculate outdoor heat stress for entire urban agglomerations for a time period spanning several months. A dedicated measurement campaign was set up to evaluate model performance, yielding satisfactory results. As an example, the modelling tool was used to assess the effectiveness of green areas and water surfaces to cool air temperatures and wet bulb globe temperatures during a typical hot day in the city of Ghent (Belgium), since the use of vegetation and water bodies are shown to be promising in mitigating the adverse effects of urban heat islands and improving thermal comfort. The results show that air temperature reduction is most profound over water surfaces during the afternoon, while open rural areas are coolest during the night. Radiation shading from trees, and to a lesser extent, from buildings, is found to be most effective in reducing wet bulb globe temperatures and improving thermal comfort during the warmest moments of the day.

scholarly journals Use of remote sensing in the identification of Urban Heat Islands and in the evaluation of Human Thermal Comfort

2018 ◽  
Vol 7 (7) ◽  
pp. 408
Author(s):  
Rafaela Lisboa Costa
Keyword(s):  
Remote Sensing ◽  
Heat Stress ◽  
Surface Temperature ◽  
Thermal Comfort ◽  
Urban Areas ◽  
Satellite Images ◽  
Urban Heat Islands ◽  
Heat Islands ◽  
Human Thermal Comfort ◽  
Urban Heat

The objective of this study was to identify heat islands and to evaluate the degree of thermal comfort / discomfort in selected urban areas. Landsat 5 and 8 satellite images were use in the thermal bands and, as a complement, observed data from meteorological stations present in the chosen cities. In order to evaluate heat islands and the degree of thermal comfort / discomfort, the surface temperature was obtain and the Kawamura Discomfort Index (IDK) was use. By means of surface temperature images, it was possible to identify the heat islands in these areas. For IDK, in spite of this index, in general, to present the situation of comfort, for some areas were observe situations of discomfort and heat stress due to the heat, mainly in the year of 2016, considered one of the hottest of this century. The use of observed data was necessary in order to corroborate with the information of the satellites.

scholarly journals Characterization of human thermal comfort in urban areas of brazilian semiarid

2015 ◽  
Vol 30 (4) ◽  
pp. 371-380 ◽  
Author(s):  
Pedro Vieira de Azevedo ◽  
Péricles Tadeu da Costa Bezerra ◽  
Mário de Miranda Vilas Boas Ramos Leitão ◽  
Carlos Antonio Costa dos Santos
Keyword(s):  
Thermal Comfort ◽  
Rural Areas ◽  
Urban Areas ◽  
Experimental Studies ◽  
Urban Heat Islands ◽  
Semiarid Region ◽  
Urban Structure ◽  
Thermal Discomfort ◽  
Human Thermal Comfort ◽  
Brazilian Semiarid

ABSTRACT Experimental studies were conducted aiming to characterize the thermal conditions in urban areas of the Brazilian semiarid for identifying the level of human thermal comfort in urban areas of the municipalities of Mossoró-RN, Serra Talhada-PE, Petrolina-PE and Juazeiro-BA. The results showed that the constituent elements of urban areas contribute to human thermal discomfort index (DIT). Both the wet and dry seasons showed up an uncomfortable condition in Mossoró on May 15th and on 23rd, 2008 (rural area) and on May 25rd, 2008 (urban area). By applying Thom's equation for obtaining the DIT, it was observed that the urban areas reported thermal comfort conditions always inferior to those observed in the rural areas. The results indicate conditions of partial comfort for the all areas surveyed. However, the incidence of human thermal discomfort related to the minimum, average and maximum air temperatures are, probably associated to the formation of urban heat islands. In addition, the afforestation is an effective mechanism of mitigating the adverse effects of these structures with better quality of life to the population. Therefore, it can be stated that the Brazilian semiarid region has specific urban climate, which is influenced by the design characteristics of the urban structure and buildings.

scholarly journals Future Changes in Human-Biometeorological Index Classes in Three Regions of Luxembourg, Western-Central Europe

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hanna Leona Lokys ◽  
Jürgen Junk ◽  
Andreas Krein
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Thermal Stress ◽  
Thermal Comfort ◽  
Central Europe ◽  
Spatial Resolution ◽  
Climate Index ◽  
Human Thermal Comfort ◽  
Air Temperatures ◽  
The Impact

Projected climate change will cause increasing air temperatures affecting human thermal comfort. In the highly populated areas of Western-Central Europe a large population will be exposed to these changes. In particular Luxembourg—with its dense population and the large cross-border commuter flows—is vulnerable to changing thermal stress. Based on climate change projections we assessed the impact of climate change on human thermal comfort over the next century using two common human-biometeorological indices, the Physiological Equivalent Temperature and the Universal Thermal Climate Index. To account for uncertainties, we used a multimodel ensemble of 12 transient simulations (1971–2098) with a spatial resolution of 25 km. In addition, the regional differences were analysed by a single regional climate model run with a spatial resolution of 1.3 km. For the future, trends in air temperature, vapour pressure, and both human-biometeorological indices could be determined. Cold stress levels will decrease significantly in the near future up to 2050, while the increase in heat stress turns statistically significant in the far future up to 2100. This results in a temporarily reduced overall thermal stress level but further increasing air temperatures will shift the thermal comfort towards heat stress.

Automated detection of urban heat islands based on satellite imagery, digital surface models, and a low-cost sensor network                                     

2021 ◽  
Author(s):  
Sebastian Schlögl ◽  
Nico Bader ◽  
Julien Gérard Anet ◽  
Martin Frey ◽  
Curdin Spirig ◽  
...  
Keyword(s):  
Climate Change ◽  
Air Temperature ◽  
Rural Areas ◽  
Urban Areas ◽  
Low Cost ◽  
Urban Heat Islands ◽  
Heat Islands ◽  
Micro Scale ◽  
Air Temperatures ◽  
Urban Heat

<p>Today, more than half of the world’s population lives in urban areas and the proportion is projected to increase further in the near future. The increased number of heatwaves worldwide caused by the anthropogenic climate change may lead to heat stress and significant economic and ecological damages. Therefore, the growth of urban areas in combination with climate change can increase future mortality rates in cities, given that cities are more vulnerable to heatwaves due to the greater heat storage capacity of artificial surfaces towards higher longwave radiation fluxes.</p><p>To detect urban heat islands and resolve the micro-scale air temperature field in an urban environment, a low-cost air temperature network, including 450 sensors, was installed in the Swiss cities of Zurich and Basel in 2019 and 2020. These air temperature data, complemented with further official measurement stations, force a statistical air temperature downscaling model for urban environments, which is used operationally to calculate hourly micro-scale air temperatures in 10 m horizontal resolution. In addition to air temperature measurements from the low-cost sensor network, the model is further forced by albedo, NDVI, and NDBI values generated from the polar-orbiting satellite Sentinel-2, land surface temperatures estimated from Landsat-8, and high-resolution digital surface and elevation models.</p><p>Urban heat islands (UHI) are processed averaging hourly air temperatures over an entire year for each grid point, and comparing this average to the overall average in rural areas. UHI effects can then be correlated to high-resolution local climate zone maps and other local factors.</p><p>Between 60-80 % of the urban area is modeled with an accuracy below 1 K for an hourly time step indicating that the approach may work well in different cities. However, the outcome may depend on the complexity of the cities. The model error decreases rapidly by increasing the number of spatially distributed sensor data used to train the model, from 0 to 70 sensors, and then plateaus with further increases. An accuracy below 1 K can be expected for more than 50 air temperature measurements within the investigated cities and the surrounding rural areas. </p><p>A strong statistical air temperature model coupled with atmospheric boundary layer models (e.g. PALM-4U, MUKLIMO, FITNAH) will aid to generate highly resolved urban heat island prediction maps that help decision-makers to identify local heat islands easier. This will ensure that financial resources will be invested as efficiently as possible in mitigation actions.</p>

scholarly journals What is the most threatening for citizens of a mid-latitude city: cold stress or heat stress?

2021 ◽  
Author(s):  
Sara Top ◽  
Dragan Milošević ◽  
Steven Caluwaerts ◽  
Stevan Savić
Keyword(s):  
Heat Stress ◽  
Cold Stress ◽  
Thermal Comfort ◽  
Heat Wave ◽  
Outdoor Thermal Comfort ◽  
Belgian Society ◽  
Human Thermal Comfort ◽  
Summer Heat ◽  
Heat And Cold Stress ◽  
The City

<p>Both heat and cold waves cause extreme human thermal discomfort and a clear excess in mortality. This shows the importance of knowing the prevailing thermal comfort conditions and how thermal comfort conditions vary in various environments so measures can be taken. Microclimatic and outdoor human thermal comfort conditions are investigated in various built-up and green areas in the city of Ghent (Belgium) using meteorological measurements of six weather stations of the MOCCA (Monitoring the Cities Climate and Atmosphere) network in combination with calculations done by RayMan.</p><p>Normal to extreme summer heat wave periods show that dangerous strong heat stress prevails during the daytime periods at all locations. Comparison of thermal comfort during normal and extreme summer heat wave periods showed that heat stress is more extreme when a heat wave is more intense. Overall the urban park in Ghent was the most comfortable location during heat waves since it effectively mitigates heat stress in the city. These results should be taken into account in urban planning and design to keep mid-latitude cities livable.</p><p>Further, a one year data series revealed that outdoor cold stress was more apparent during 2017 in the mid-latitude city of Ghent that experiences a mild maritime climate. During spring and summer, both heat stress and cold stress occurred due to the larger diurnal temperature range compared to the other seasons. Even though high Physiological Equivalent Temperatures (PET) were obtained during a heat wave in summer, heat stress did not occur as intensely and as frequently compared to cold stress on annual level. It could thus be stated that outdoors, cold stress is a bigger threat than heat stress. However, one should keep in mind that the study was executed for outdoor thermal heat comfort and that people will take shelter or take measures when feeling uncomfortable. The question is thus rather, how are citizens protected against heat and cold stress? Currently, the Belgian society is better adapted to cold stress since most buildings contain central heating, while air conditioning is not standard. Future projections predict an increase in temperature, causing more occurrence of extreme heat stress, while extreme cold stress will be reduced. Additionally, the urban heat island effect currently has mainly a positive effect on the average annual outdoor thermal comfort conditions, while it will become a negative effect in the warmer future. Measures should thus be taken to reduce the threat of future heat stress.</p>

The Benefits of Tree Shade and Turf on Globe and Surface Temperatures in an Urban Tropical Environment

2020 ◽  
Vol 46 (3) ◽  
pp. 228-244
Author(s):  
Lai Fern Ow ◽  
Subhadip Ghosh ◽  
Mohamed Lokman Mohd Yusof
Keyword(s):  
Thermal Comfort ◽  
Urban Areas ◽  
Mitigation Strategies ◽  
Urban Heat Islands ◽  
Outdoor Thermal Comfort ◽  
Mitigation Measures ◽  
Heat Islands ◽  
Ambient Temperatures ◽  
Surface Temperatures ◽  
Island State

The process of urbanisation increases temperature and alters the thermal comfort in cities. Urban heat islands (UHIs) result in the rise of ambient temperatures. For example, in the densely populated island state of Singapore, the UHI intensity was some 4.5 °C. Such elevation in heat can negatively impact outdoor thermal comfort and may give rise to serious health problems. The present study investigated the benefits of trees and turf as mitigation strategies for urban areas. Short- and long-term observations were made for surface and globe temperatures over smaller plots of vegetation and hard surfaces involving tree shade and full sun. Similar observations were investigated over a larger extent of vegetation across concrete, asphalt, and turf within an urban park setting. The presence of turf and shade from trees greatly affected surface temperatures, and the effect was most pronounced when both were present. The presence of turf reduced surface temperatures by up to 10 °C, while tree shade led to a 12 °C reduction. Globe temperatures showed that the presence of turf and shading reduced temperatures between 5 and 10 °C. These results suggest that turf and trees can effectively cool surfaces and improve outdoor thermal comfort. The results of this study can be applied to urban planning of greenery and can be used as a reference for other tropical cities with similar climates that are also working to develop mitigation measures to improve the liveability of their cities.

scholarly journals Thermal Comfort Level Assessment in Urban Area of Petrolina-PE County, Brazil

2017 ◽  
Vol 32 (4) ◽  
pp. 555-563 ◽  
Author(s):  
Pedro Vieira de Azevedo ◽  
Péricles Tadeu da Costa Bezerra ◽  
Mario de Miranda Vilas Boas Ramos Leitão ◽  
Carlos Antonio Costa dos Santos
Keyword(s):  
Thermal Comfort ◽  
Urban Area ◽  
Rural Areas ◽  
Urban Areas ◽  
Thermal Conditions ◽  
Comfort Level ◽  
Urban Heat Islands ◽  
Thermal Discomfort ◽  
Heat Islands ◽  
Urban And Rural Areas

Abstract This study evaluated the thermal conditions of urban areas in Petrolina-PE, from continuous data collected in urban and rural areas for the year of 2012. The results characterized urban heat islands (UHI) with varying intensity in urban areas, especially UHI = 5.3 °C (high intensity) occurred on April 28, 2012. It was evident that the constituent elements of urban areas contribute to the formation and expansion of UHI bringing thermal discomfort for its inhabitants. An adaptation to Thom’s equation for calculating the Thermal Discomfort Index (DIT), was used to obtain the maximum (DITx) and minimum (DITm) thermal discomfort. In the urban area, the DITm indicated thermal comfort in 23.0% of the days and partial comfort in 77.0% of days surveyed. Already, the DITx characterized 71.6% of days with partial comfort and 28.4% of days with thermal discomfort. In the rural area, The DITm indicated that 41.5% of days were thermally comfortable and 58.5% of days had partial comfort. However, the DITx pointed 87.7% of the days of this environment with partial thermal comfort and 12.3% of thermally uncomfortable days. Finally, the results showed that afforestation of urban area constitutes to an effective and efficient way to mitigate thermal discomfort.

scholarly journals Analysis of human thermal comfort in Central European City during summer of 2015: A case of Novi Sad (Serbia)

2020 ◽  
Vol 100 (1) ◽  
pp. 31-39
Author(s):  
Dragan Milosevic ◽  
Stevan Savic ◽  
Danijela Arsenovic ◽  
Zorana Luzanin ◽  
Jelena Dunjic
Keyword(s):  
Heat Stress ◽  
Thermal Comfort ◽  
Extreme Heat ◽  
Outdoor Thermal Comfort ◽  
European City ◽  
Central European ◽  
Human Thermal Comfort ◽  
Local Climate Zones ◽  
Novi Sad ◽  
Extreme Heat Stress

Urban meteorological network (UMN) was established in the Central European City of Novi Sad (Serbia) based on "local climate zones" (LCZs) system. Physiologically Equivalent Temperature (PET) index was used for the assessment of outdoor thermal comfort in the "built" and "land cover" LCZ classes of Novi Sad. The index was calculated in the RayMan software based on the meteorological, physiological as well as building and vegetation data. Temporal analysis was performed for extreme heat stress days (PETmax ? 41 ?C), extreme heat stress hours (PETav ? 41 ?C) and days with occurrence of "tropical nights" (Tmin > 20 ?C) during exceptionally hot summer of 2015. Our results show that extreme heat stress hours are the least frequent in compact midrise LCZ 2, followed by dense trees LCZ A. On the contrary, countryside (low plants - LCZ D) showed to be the most uncomfortable area during daytime followed by compact low-rise areas (LCZ 3). Tropical nights are the most frequent in midrise LCZs 5 and 2 (40-46 nights) and decreasing towards open, sparsely built and natural LCZs (6-8 tropical nights in LCZs A and D). This is almost 800% decrease and it has implications for health and recreation of urban population and emphasizes the need for UMN development based on LCZ system.

scholarly journals U.K. Climate Projections: Summer Daytime and Nighttime Urban Heat Island Changes in England’s Major Cities

2020 ◽  
Vol 33 (20) ◽  
pp. 9015-9030
Author(s):  
Y. T. Eunice Lo ◽  
Daniel M. Mitchell ◽  
Sylvia I. Bohnenstengel ◽  
Mat Collins ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Time Of Day ◽  
Urban Heat Islands ◽  
Future Research ◽  
Climate Projections ◽  
Near Surface ◽  
Air Temperatures ◽  
Summer Temperatures ◽  
Urban Heat

AbstractIn the United Kingdom, where 90% of residents are projected to live in urban areas by 2050, projecting changes in urban heat islands (UHIs) is essential to municipal adaptation. Increased summer temperatures are linked to increased mortality. Using the new regional U.K. Climate Projections, UKCP18-regional, we estimate the 1981–2079 trends in summer urban and rural near-surface air temperatures and in UHI intensities during day and at night in the 10 most populous built-up areas in England. Summer temperatures increase by 0.45°–0.81°C per decade under RCP8.5, depending on the time of day and location. Nighttime temperatures increase more in urban than rural areas, enhancing the nighttime UHI by 0.01°–0.05°C per decade in all cities. When these upward UHI signals emerge from 2008–18 variability, positive summer nighttime UHI intensities of up to 1.8°C are projected in most cities. However, we can prevent most of these upward nighttime UHI signals from emerging by stabilizing climate to the Paris Agreement target of 2°C above preindustrial levels. In contrast, daytime UHI intensities decrease in nine cities, at rates between −0.004° and −0.05°C per decade, indicating a trend toward a reduced daytime UHI effect. These changes reflect different feedbacks over urban and rural areas and are specific to UKCP18-regional. Future research is important to better understand the drivers of these UHI intensity changes.

scholarly journals Using Climate-Sensitive 3D City Modeling to Analyze Outdoor Thermal Comfort in Urban Areas

2020 ◽  
Vol 9 (11) ◽  
pp. 688
Author(s):  
SeyedehRabeeh HosseiniHaghighi ◽  
Fatemeh Izadi ◽  
Rushikesh Padsala ◽  
Ursula Eicker
Keyword(s):  
Climate Change ◽  
Heat Stress ◽  
Thermal Comfort ◽  
Urban Areas ◽  
Assessment Model ◽  
Three Dimensions ◽  
Outdoor Thermal Comfort ◽  
Effective Response ◽  
Climate Assessment ◽  
City Modeling

With increasing urbanization, climate change poses an unprecedented threat, and climate-sensitive urban management is highly demanded. Mitigating climate change undoubtedly requires smarter urban design tools and techniques than ever before. With the continuous evolution of geospatial technologies and an added benefit of analyzing and virtually visualizing our world in three dimensions, the focus is now shifting from a traditional 2D to a more complicated 3D spatial design and assessment with increasing potential of supporting climate-responsive urban decisions. This paper focuses on using 3D city models to calculate the mean radiant temperature (Tmrt) as an outdoor thermal comfort indicator in terms of assessing the spatiotemporal distribution of heat stress on the district scale. The analysis is done to evaluate planning scenarios for a district transformation in Montreal/Canada. The research identifies a systematic workflow to assess and upgrade the outdoor thermal comfort using the contribution of ArcGIS CityEngine for 3D city modeling and the open-source model of solar longwave environmental irradiance geometry (SOLWEIG) as the climate assessment model. A statistically downscaled weather profile for the warmest year predicted before 2050 (2047) is used for climate data. The outcome shows the workflow capacity for the structured recognition of area under heat stress alongside supporting the efficient intervention, the tree placement as a passive strategy of heat mitigation. The adaptability of workflow with the various urban scale makes it an effective response to the technical challenges of urban designers for decision-making and action planning. However, the discovered technical issues in data conversion and wall surface albedo processing call for the climate assessment model improvement as future demand.

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