scholarly journals Quantifying the Effect of Building Shadowing and Cloudiness on Mean Radiant Temperature in Singapore

Atmosphere ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1012
Author(s):  
Juan A. Acero ◽  
Elliot J. Y. Koh ◽  
Yon Sun Tan ◽  
Leslie K. Norford
Keyword(s):  
Urban Areas ◽  
Thermal Environment ◽  
Monsoon Season ◽  
Outdoor Thermal Comfort ◽  
View Factor ◽  
Detailed Knowledge ◽  
Mean Radiant Temperature ◽  
Diffuse Solar Radiation ◽  
Radiant Temperature ◽  
The Impact

Improving the quality of life in urban areas has become a major concern in the last few decades. With a constantly increasing urban population and in a climate change context, detailed knowledge of the impact of urban elements on the outdoor thermal environment is relevant. In this work, we present the results of several climatic campaigns carried out in Singapore aiming to evaluate local urban climate variables. Sensors were deployed simultaneously in different sites. The effect of building shadowing in the diurnal cycle of mean radiant temperature (Tmrt) is evaluated in different seasons. Although during the Inter-Monsoon season, mean Tmrt reduction due to building shadow is ≈19 °C, during clear skies days, it can be reduced by ≈30 °C. The Tmrt difference between sites is analyzed based on the weather conditions, the sky view factor (SVF), and the type of surrounding urban elements. Under building shadow conditions, higher SVF showed higher Tmrt values, although no correlation was found between Tmrt and diffuse solar radiation (measured above the urban canopy). The results suggest a relevant contribution of other radiation components (e.g., longwave radiation). The quantitative analysis of the Tmrt provided in this work is relevant for outdoor thermal comfort strategies in tropical areas such as Singapore.

scholarly journals Thermal and Geometric Controls on the Rate of Surface Air Temperature Changes in a Medium-Sized, Midlatitude City

2007 ◽  
Vol 46 (2) ◽  
pp. 241-247 ◽  
Author(s):  
Tomohiko Tomita ◽  
Hiroyuki Kusaka ◽  
Ryo Akiyoshi ◽  
Yoshiyuki Imasato
Keyword(s):  
Time Dependence ◽  
Air Temperature ◽  
Urban Areas ◽  
Mesoscale Model ◽  
Thermal Environment ◽  
Surface Air Temperature ◽  
Anthropogenic Heat ◽  
View Factor ◽  
Temperature Changes ◽  
The Impact

Abstract Gradual cooling in the evening forms a wintertime nocturnal urban heat island. This work, with a mesoscale model involving urban canopy physics, is an examination of how four thermal and geometric controls—anthropogenic heat QF, heat capacity C, thermal conductivity k, and sky-view factor ψs—modify the rate of surface air temperature changes ΔT/Δt. In particular, the time dependence is diagnosed through numerical experiments. The controls QF and k are major agents in the evening, when QF changes the evening ΔT/Δt linearly and k is logarithmic. The effects of C and ψs are large in the morning and in the afternoon with those of k. The impact of QF is, however, substantial only in the evening. Because the time dependence of C and k is different, the thermal inertia used as a parameter in the urban climate studies should be divided into two parameters: C and k. To improve the thermal environment in urban areas, the modification of QF and k could be effective.

scholarly journals Modeling Mean Radiant Temperature Distribution in Urban Landscapes Using DART

2021 ◽  
Vol 13 (8) ◽  
pp. 1443
Author(s):  
Maria Angela Dissegna ◽  
Tiangang Yin ◽  
Hao Wu ◽  
Nicolas Lauret ◽  
Shanshan Wei ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Thermal Comfort ◽  
Leaf Area ◽  
Remote Sensing Data ◽  
Outdoor Thermal Comfort ◽  
Transfer Model ◽  
Mean Radiant Temperature ◽  
Area Index ◽  
Sensing Data ◽  
Radiant Temperature

The microclimatic conditions of the urban environment influence significantly the thermal comfort of human beings. One of the main human biometeorology parameters of thermal comfort is the Mean Radiant Temperature (Tmrt), which quantifies effective radiative flux reaching a human body. Simulation tools have proven useful to analyze the radiative behavior of an urban space and its impact on the inhabitants. We present a new method to produce detailed modeling of Tmrt spatial distribution using the 3-D Discrete Anisotropic Radiation Transfer model (DART). Our approach is capable to simulate Tmrt at different scales and under a range of parameters including the urban pattern, surface material of ground, walls, roofs, and properties of the vegetation (coverage, shape, spectral signature, Leaf Area Index and Leaf Area Density). The main advantages of our method are found in (1) the fine treatment of radiation in both short-wave and long-wave domains, (2) detailed specification of optical properties of urban surface materials and of vegetation, (3) precise representation of the vegetation component, and (4) capability to assimilate 3-D inputs derived from multisource remote sensing data. We illustrate and provide a first evaluation of the method in Singapore, a tropical city experiencing strong Urban Heat Island effect (UHI) and seeking to enhance the outdoor thermal comfort. The comparison between DART modelled and field estimated Tmrt shows good agreement in our study site under clear-sky condition over a time period from 10:00 to 19:00 (R2 = 0.9697, RMSE = 3.3249). The use of a 3-D radiative transfer model shows promising capability to study urban microclimate and outdoor thermal comfort with increasing landscape details, and to build linkage to remote sensing data. Our methodology has the potential to contribute towards optimizing climate-sensitive urban design when combined with the appropriate tools.

scholarly journals How Can We Adapt Thermal Comfort for Disabled Patients? A Case Study of French Healthcare Buildings in Summer

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4530
Author(s):  
Youcef Bouzidi ◽  
Zoubayre El Akili ◽  
Antoine Gademer ◽  
Nacef Tazi ◽  
Adil Chahboun
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Residential Buildings ◽  
Linear Regression Analysis ◽  
Environmental Parameters ◽  
Physical Parameters ◽  
Mean Radiant Temperature ◽  
Operative Temperature ◽  
Neutral Temperature ◽  
Radiant Temperature

This paper investigates adaptive thermal comfort during summer in medical residences that are located in the French city of Troyes and managed by the Association of Parents of Disabled Children (APEI). Thermal comfort in these buildings is evaluated using subjective measurements and objective physical parameters. The thermal sensations of respondents were determined by questionnaires, while thermal comfort was estimated using the predicted mean vote (PMV) model. Indoor environmental parameters (relative humidity, mean radiant temperature, air temperature, and air velocity) were measured using a thermal environment sensor during the summer period in July and August 2018. A good correlation was found between operative temperature, mean radiant temperature, and PMV. The neutral temperature was determined by linear regression analysis of the operative temperature and Fanger’s PMV model. The obtained neutral temperature is 23.7 °C. Based on the datasets and questionnaires, the adaptive coefficient α representing patients’ capacity to adapt to heat was found to be 1.261. A strong correlation was also observed between the sequential thermal index n(t) and the adaptive temperature. Finally, a new empirical model of adaptive temperature was developed using the data collected from a longitudinal survey in four residential buildings of APEI in summer, and the obtained adaptive temperature is 25.0 °C with upper and lower limits of 24.7 °C and 25.4 °C.

scholarly journals Biomimicry-Based Strategies for Urban Heat Island Mitigation: A Numerical Case Study under Tropical Climate

Biomimetics ◽  
2021 ◽  
Vol 6 (3) ◽  
pp. 48
Author(s):  
Kevin Araque ◽  
Paola Palacios ◽  
Dafni Mora ◽  
Miguel Chen Austin
Keyword(s):  
Thermal Comfort ◽  
Urban Heat Island ◽  
Urban Areas ◽  
Outdoor Thermal Comfort ◽  
Base Case ◽  
Heat Island ◽  
Urban Heat ◽  
Historical Heritage ◽  
Pet Index ◽  
Radiant Temperature

In recent years, demographic growth has caused cities to expand their urban areas, increasing the risk of overheating, creating insurmountable microclimatic conditions within the urban area, which is why studies have been carried out on the urban heat island effect (UHI) and its mitigation. Therefore, this research aims to evaluate the cooling potential in the application of strategies based on biomimicry for the microclimate in a historical heritage city of Panama. For this, three case studies (base case, case 1, and case 2) of outdoor thermal comfort were evaluated, in which the Envi-met software was used to emulate and evaluate the thermal performance of these strategies during March (highest temperature month) and October (rainier month). The strategies used were extracted from the contrast of zebra skin, human skin, evaporative cooling, and ant skin. The results showed a reduction of 2.8 °C in the air temperature at 11:00, the radiant temperature decreased by 2.2 °C, and the PET index managed to reduce the thermal comfort indicator among its categories. The importance of thinking based on biomimicry in sustainable strategies is concluded; although significant changes were obtained, high risks of discomfort persist due to the layout and proximity of the building.

Design Range of Indoor Relative Humidity in Radiant Cooling Environment

2011 ◽  
Vol 243-249 ◽  
pp. 4905-4908
Author(s):  
Xue Min Sui ◽  
Xu Zhang ◽  
Guang Hui Han
Keyword(s):  
Relative Humidity ◽  
Thermal Comfort ◽  
Mean Radiant Temperature ◽  
Design Standards ◽  
Human Thermal Comfort ◽  
Radiant Cooling ◽  
Climate Parameter ◽  
Radiant Temperature ◽  
Thermal Comfort Model ◽  
The Impact

Relative humidity is an important micro-climate parameter in radiant cooling environment. Based on the human thermal comfort model, this paper studied the effect on PMV index of relative humidity, and studied the relationship of low mean radiant temperature and relative humidity, drew the appropriate design range of indoor relative humidity for radiant cooling systems.The results show that high relative humidity can compensate for the impact on thermal comfort of low mean radiant temperature, on the premise of achieving the same thermal comfort requirements. However, because of the limited compensation range of relative humidity, together with the constraints for it due to anti-condensation of radiant terminal devices, the design range of relative humidity should not be improved, and it can still use the traditional air-conditioning design standards.

scholarly journals Estimation of Mean Radiant Temperature in Urban Canyons Using Google Street View: A Case Study on Seoul

2022 ◽  
Vol 14 (2) ◽  
pp. 260
Author(s):  
Eun-Sub Kim ◽  
Seok-Hwan Yun ◽  
Chae-Yeon Park ◽  
Han-Kyul Heo ◽  
Dong-Kun Lee
Keyword(s):  
Heat Stress ◽  
Spatial Patterns ◽  
High Density ◽  
View Factor ◽  
Mean Radiant Temperature ◽  
Street Canyons ◽  
Google Street View ◽  
Street Level ◽  
Street View ◽  
Radiant Temperature

Extreme heat exposure has severe negative impacts on humans, and the issue is exacerbated by climate change. Estimating spatial heat stress such as mean radiant temperature (MRT) is currently difficult to apply at city scale. This study constructed a method for estimating the MRT of street canyons using Google Street View (GSV) images and investigated its large-scale spatial patterns at street level. We used image segmentation using deep learning to calculate the view factor (VF) and project panorama into fisheye images. We calculated sun paths to estimate MRT using panorama images from Google Street View. This paper shows that regression analysis can be used to validate between estimated short-wave, long-wave radiation and the measurement data at seven field measurements in the clear-sky (0.97 and 0.77, respectively). Additionally, we compared the calculated MRT and land surface temperature (LST) from Landsat 8 on a city scale. As a result of investigating spatial patterns of MRT in Seoul, South Korea, we found that a high MRT of street canyons (>59.4 °C) is mainly distributed in open space areas and compact low-rise density buildings where the sky view factor is 0.6–1.0 and the building view factor (BVF) is 0.35–0.5, or west-east oriented street canyons with an SVF of 0.3–0.55. However, high-density buildings (BVF: 0.4–0.6) or high-density tree areas (Tree View Factor, TVF: 0.6–0.99) showed low MRT (<47.6). The mapped MRT results had a similar spatial distribution to the LST; however, the MRT was lower than the LST in low tree density or low-rise high-density building areas. The method proposed in this study is suitable for a complex urban environment consisting of buildings, trees, and streets. This will help decision makers understand spatial patterns of heat stress at the street level.

scholarly journals Quantifying the Effects of Urban Form on Land Surface Temperature in Subtropical High-Density Urban Areas Using Machine Learning

2019 ◽  
Vol 11 (8) ◽  
pp. 959 ◽  
Author(s):  
Yanwei Sun ◽  
Chao Gao ◽  
Jialin Li ◽  
Run Wang ◽  
Jian Liu
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Urban Form ◽  
Urban Areas ◽  
Thermal Environment ◽  
High Density ◽  
Cooling Effects ◽  
Urban Thermal Environment ◽  
The Impact

It is widely acknowledged that urban form significantly affects urban thermal environment, which is a key element to adapt and mitigate extreme high temperature weather in high-density urban areas. However, few studies have discussed the impact of physical urban form features on the land surface temperature (LST) from a perspective of comprehensive urban spatial structures. This study used the ordinary least-squares regression (OLS) and random forest regression (RF) to distinguish the relative contributions of urban form metrics on LST at three observation scales. Results of this study indicate that more than 90% of the LST variations were explained by selected urban form metrics using RF. Effects of the magnitude and direction of urban form metrics on LST varied with the changes of seasons and observation scales. Overall, building morphology and urban ecological infrastructure had dominant effects on LST variations in high-density urban centers. Urban green space and water bodies demonstrated stronger cooling effects, especially in summer. Building density (BD) exhibited significant positive effects on LST, whereas the floor area ratio (FAR) showed a negative influence on LST. The results can be applied to investigate and implement urban thermal environment mitigation planning for city managers and planners.

Modelling the impact of increased street tree cover on mean radiant temperature across Vancouver’s local climate zones

2019 ◽  
Vol 39 ◽  
pp. 9-17 ◽  
Author(s):  
Mehdi Aminipouri ◽  
Anders Jensen Knudby ◽  
E. Scott Krayenhoff ◽  
Kirsten Zickfeld ◽  
Ariane Middel
Keyword(s):  
Tree Cover ◽  
Mean Radiant Temperature ◽  
Climate Zones ◽  
Local Climate ◽  
Street Tree ◽  
Local Climate Zones ◽  
Radiant Temperature ◽  
The Impact

scholarly journals The most problematic variable in the course of human-biometeorological comfort assessment — the mean radiant temperature

2011 ◽  
Vol 3 (1) ◽  
Author(s):  
Noémi Kántor ◽  
János Unger
Keyword(s):  
Thermal Comfort ◽  
Short Wave ◽  
Urban Environments ◽  
Outdoor Thermal Comfort ◽  
Radiation Environment ◽  
Wave Radiation ◽  
Mean Radiant Temperature ◽  
Radiation Fluxes ◽  
The Mean ◽  
Radiant Temperature

AbstractThis paper gives a review on the topic of the mean radiant temperature Tmrt, the most important parameter influencing outdoor thermal comfort during sunny conditions. Tmrt summarizes all short wave and long wave radiation fluxes reaching the human body, which can be very complex (variable in spatial and also in temporal manner) in urban settings. Thermal comfort researchers and urban planners need easy and sound methodological approaches to assess Tmrt. After the basics of the Tmrt calculation some of the methods suitable for obtaining Tmrt also in urban environments will be presented.. Two of the discussed methods are based on instruments which measure the radiation fluxes integral (globe thermometer, pyranometer-pyrgeometer combination), and three of the methods are based on modelling the radiation environment with PC software (RayMan, ENVI-met and SOLWEIG).

scholarly journals CityComfort+: A simulation-based method for predicting mean radiant temperature in dense urban areas

2014 ◽  
Vol 80 ◽  
pp. 84-95 ◽  
Author(s):  
Jianxiang Huang ◽  
Jose Guillermo Cedeño-Laurent ◽  
John D. Spengler
Keyword(s):  
Urban Areas ◽  
Mean Radiant Temperature ◽  
Simulation Based ◽  
Radiant Temperature
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