scholarly journals Influence of Weather Factors on Thermal Comfort in Subtropical Urban Environments

2020 ◽  
Vol 12 (5) ◽  
pp. 2001 ◽  
Author(s):  
Chih-Hong Huang ◽  
Hsin-Hua Tsai ◽  
Hung-chen Chen
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Thermal Environment ◽  
Urban Environments ◽  
Heat Island ◽  
Weather Factors ◽  
Urban Forms ◽  
Thermal Environments ◽  
Island Effect ◽  
Urban Heat

Urbanization has influenced the distribution of heat in urban environments. The mutual influence between weather factors and urban forms created by dense buildings intensify human perception of the deteriorating thermal environment in subtropics. Past studies have used real-world measurements and theoretical simulations to understand the relationship between climate factors and the urban heat island effect. However, few studies have examined how weather factors and urban forms are connected to the thermal environment. To understand the influence of various weather factors on urban thermal environments in various urban forms, this study applied structural equation modeling to assumptions of linear relationships and used quantitative statistical analysis of weather data as well as structural conversion of this data to establish the structural relationships between variables. Our objective was to examine the relationships among urban forms, weather factors, and thermal comfort. Our results indicate that weather factors do indeed exert influence on thermal comfort in urban environments. In addition, the thermal comfort of urban thermal environments varies with location and building density. In hot and humid environments in the subtropics, humidity and wind speed have an even more profound impact on the thermal environment. Apparent temperature can be used to examine differences in thermal comfort and urban forms. This study also proved that an urban wind field can effectively mitigate the urban heat island effect. Ventilation driven by wind and thermal buoyancy can dissipate heat islands and take the heat away from urban areas.

scholarly journals Impact of urbanization on thermal environment of Chengdu-Chongqing Urban Agglomeration under complex terrain

2021 ◽  
Author(s):  
Si Chen ◽  
Zhenghui Xie ◽  
Jinbo Xie ◽  
Bin Liu ◽  
Binghao Jia ◽  
...  
Keyword(s):  
Urban Heat Island ◽  
Urban Area ◽  
Complex Terrain ◽  
Thermal Environment ◽  
Urban Agglomeration ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Island Effect ◽  
The Future ◽  
Urban Heat

Abstract. Located in the mountainous area of southwest China, the Chengdu-Chongqing Urban Agglomeration (CCUA) was rapidly urbanized in the last four decades, has led to a three-fold urban area expansion, thereby affecting the weather and climate. To investigate the urbanization effects on the thermal environment in the CCUA under the complex terrain, we conducted the simulations using the advanced Weather Research and Forecasting (WRF V4.1.5) model together with the combining land-use scenarios and terrain conditions. We observed that the WRF model reproduces the general synoptic summer weather pattern, particularly for the thermal environment. It was shown that the expansion of the urban area changed the underlying surface's thermal properties, leading to the urban heat island effect, enhanced by the complex terrain further. The simulation with the future scenario shows that the implementation of idealized measures including returning farmland to forests, expanding rivers and lakes can reduce the urban heat island effect and regulate the urban ecosystem. Therefore, the urban planning policy can has potential to provide feasible suggestions to best manage the thermal environment of the future city toward improving the livelihood of the people in the environment.

Numerical Simulation on Cooling Effects of Greening for Alleviating Urban Heat Island Effect in North China

2014 ◽  
Vol 675-677 ◽  
pp. 1227-1233 ◽  
Author(s):  
Cheng Chen ◽  
Yu Yue ◽  
Wen Jiang
Keyword(s):  
Numerical Simulation ◽  
Computer Simulation ◽  
Urban Heat Island ◽  
North China ◽  
Thermal Environment ◽  
Heat Island ◽  
Island Effect ◽  
Outdoor Thermal Environment ◽  
Urban Heat ◽  
Cooling Effects

As the climate warming up, the effects of the urban heat island have been an insurmountable issue in the urban development. In this paper, taking Tianjin for example, the research combined computer simulation with on-site measurement to evaluate the effects of different greening ratios on outdoor thermal environment. Besides, the accuracy of the simulation model has been verified by calibration. Research results determined that the increase of the greening ratio in the existing environment could improve the outdoor thermal environment in summer. But the limitations of green cooling was also pointed out, namely that the air temperature would infinitely close to a certain value with further increasing greening ratio.

The Performance of Low-Heat Accumulation Asphalt Mixture and the Evaluation Model of its Thermal Effect on Cities

2011 ◽  
Vol 287-290 ◽  
pp. 1795-1804 ◽  
Author(s):  
Jian Guang Xie ◽  
Zhao Xu Yang ◽  
Xiao Qing Fang ◽  
Ye Hu
Keyword(s):  
Surface Temperature ◽  
Urban Heat Island ◽  
Thermal Environment ◽  
Temperature Stability ◽  
Atmospheric Temperature ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Heat Accumulation ◽  
Island Effect ◽  
Urban Heat

A new type of low-heat accumulation asphalt concrete material has been made to reduce urban surface temperature and to ease the urban heat island effect. The test has investigated the temperature reduction performance and pavement performance, established a non-gray model of the atmospheric temperature field, and evaluated its effect on the urban thermal environment. The results show that compare specimens mixed with infrared powder with normal ones, the higher the infrared powder content, the lower the surface temperature, but the cooling rate decreases; the properties of high-temperature stability, low-temperature stability and water stability are improved; under the same temperature and humidity conditions, the surface layer temperature of the former pavement is lower generally; under the same radiation conditions, the surface equilibrium temperature of the former ones is 8.12K lower, which can reduce the near-earth atmospheric temperature and ease the urban heat island effect.

scholarly journals Bioclimatic Architecture and Urban Morphology. Studies on Intermediate Urban Open Spaces

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5819
Author(s):  
Alessandra Battisti
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Well Being ◽  
Urban Morphology ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Open Spaces ◽  
Physiological Equivalent Temperature ◽  
Island Effect ◽  
Urban Heat

This paper deals with the interactions between biophysical and microclimatic factors on the one hand with, on the other, the urban morphology of intermediate urban open spaces, the relationship between environmental and bioclimatic thermal comfort, and the implementation of innovative materials and the use of greenery, aimed at the users’ well-being. In particular, the thermal comfort of the open spaces of the consolidated fabrics of the city of Rome is studied, by carrying out simulations of cooling strategies relating to two scenarios applied to Piazza Bainsizza. The first scenario involves the use of cool materials for roofs, cladding surfaces, and pavement, while the second scenario, in addition to the cool materials employed in the first scenario, also includes the use of greenery and permeable green surfaces. The research was performed using summer and winter microclimatic simulations of the CFD (ENVI-met v. 3.1) type, in order to determine the different influences of the materials with cold colors, trees, and vegetated surfaces on the thermal comfort of the urban morphology itself. Meanwhile, the comfort assessment was determined through the physiological equivalent temperature (PET) calculated with the RayMan program. The first scenario, with the use of cool materials, improves summer conditions and reduces the urban heat island effect but does not eliminate thermal discomfort due to the lack of shaded surfaces and vegetation. The second scenario, where material renovations is matched with vegetation improvements, has a slightly bad effect on winter conditions but drastically ameliorates the summer situation, both for direct users and, thanks to the strong reduction of the urban heat island effect, to urban inhabitants as a whole.

scholarly journals Simplified Numerical Model for Analyzing the Effects of the Urban Heat Island upon Low-Rise Buildings by Using a Free-License Thermal Simulation Program

Urban Science ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 30
Author(s):  
Ivan Oropeza-Perez
Keyword(s):  
Numerical Model ◽  
Thermal Comfort ◽  
Urban Heat Island ◽  
Thermal Simulation ◽  
Urban Heat Island Effect ◽  
Heat Island ◽  
Indoor Temperature ◽  
Indoor Thermal Comfort ◽  
Island Effect ◽  
Urban Heat

In this document, the thermal effect of a heat island upon an urban area and its surrounding low-rise buildings is analyzed with the building thermal simulation program EnergyPlus and its EnergyPlus weather files (EPW). By using a top-down approach, a simplified numerical model is developed, which is used to simulate the urban heat island effect, and that deals with the performance of various cooling methods according to the physical, urban, and climatic characteristics of the urban site. The calculated results of outdoor air temperature considering the heat island effect achieve good agreement with the already-published results. Then, different methods of shading and cooling, varying physical values such as urban thermal transmittance, and urban thermal absorption are applied in order to find the most influencing feature upon the indoor temperature drop into a simulation loop. With this, it is found that a maximum average decrease of indoor temperature of 5.1 °C can be achieved. Furthermore, carrying out a sensitivity analysis, it is found that the albedo of both building surface and urban layout is the most influencing parameter onto the indoor thermal comfort. With this, it is expected to have a reliable model that helps to understand the urban heat island effect in a simple and cheap manner and in terms of the indoor thermal comfort of its surrounding buildings.

OVERVIEW OF URBAN HEAT ISLAND (UHI) PHENOMENON TOWARDS HUMAN THERMAL COMFORT

2017 ◽  
Vol 16 (9) ◽  
pp. 2097-2111 ◽  
Author(s):  
Mohanadoss Ponraj ◽  
Yee Yong Lee ◽  
Mohd Fadhil Md Din ◽  
Zainura Zainon Noor ◽  
Kenzo Iwao ◽  
...  
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Heat Island ◽  
Human Thermal Comfort ◽  
Urban Heat

scholarly journals Cooling Effect of Different Land Cover Types: A Case Study in Xi’an and Xianyang, China

2021 ◽  
Vol 13 (3) ◽  
pp. 1099
Author(s):  
Yuhe Ma ◽  
Mudan Zhao ◽  
Jianbo Li ◽  
Jian Wang ◽  
Lifa Hu
Keyword(s):  
Land Cover ◽  
Surface Temperature ◽  
Urban Heat Island ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Cooling Effect ◽  
Heat Island ◽  
Land Cover Types ◽  
Island Effect ◽  
Urban Heat

One of the climate problems caused by rapid urbanization is the urban heat island effect, which directly threatens the human survival environment. In general, some land cover types, such as vegetation and water, are generally considered to alleviate the urban heat island effect, because these landscapes can significantly reduce the temperature of the surrounding environment, known as the cold island effect. However, this phenomenon varies over different geographical locations, climates, and other environmental factors. Therefore, how to reasonably configure these land cover types with the cooling effect from the perspective of urban planning is a great challenge, and it is necessary to find the regularity of this effect by designing experiments in more cities. In this study, land cover (LC) classification and land surface temperature (LST) of Xi’an, Xianyang and its surrounding areas were obtained by Landsat-8 images. The land types with cooling effect were identified and their ideal configuration was discussed through grid analysis, distance analysis, landscape index analysis and correlation analysis. The results showed that an obvious cooling effect occurred in both woodland and water at different spatial scales. The cooling distance of woodland is 330 m, much more than that of water (180 m), but the land surface temperature around water decreased more than that around the woodland within the cooling distance. In the specific urban planning cases, woodland can be designed with a complex shape, high tree planting density and large planting areas while water bodies with large patch areas to cool the densely built-up areas. The results of this study have utility for researchers, urban planners and urban designers seeking how to efficiently and reasonably rearrange landscapes with cooling effect and in urban land design, which is of great significance to improve urban heat island problem.

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