scholarly journals Correlating the Sky View Factor with the Pedestrian Thermal Environment in a Hot Arid University Campus Plaza

2021 ◽  
Vol 13 (2) ◽  
pp. 468
Author(s):  
Randa Osama Shata ◽  
Ayman Hassaan Mahmoud ◽  
Mohammad Fahmy
Keyword(s):  
Thermal Environment ◽  
Field Measurements ◽  
Urban Trees ◽  
View Factor ◽  
University Campus ◽  
Physiological Equivalent Temperature ◽  
Area Index ◽  
Comfort Index ◽  
Sky View Factor ◽  
The Impact

In hot, arid regions on university campuses, students are more vulnerable to heat stresses than in street canyons in terms of function; however, the knowledge of the impact of built environments on thermal performance is still lacking. In two summer and winter days, the shading effect of the existing urban trees pattern in a university campus in Egypt was examined to correlate their Sky View Factor (SVF) with the thermal environment, meteorology, Physiological Equivalent Temperature (PET), and Universal Thermal Comfort Index (UTCI). The ENVI-met model was used in order to assess meteorological parameters, followed by SVF calculation in the Rayman program. Meteorological field measurements validated the simulation model and measured the Leaf Area Index (LAI) of two native urban trees to model the in-situ canopies foliage. In summer, the results showed a significant direct impact of the SVF on mean radiant temperature (Tmrt), PET, and UTCI; however, the excessive shading by trees on materials with a low albedo and low wind speed could lead to a slight increase in air temperature. Meanwhile, in the winter, SVF did not affect the microclimatic variables, PET, or UTCI. The resulting insight into the correlation between SVF and Tmrt emphasizes the importance of urban trees in modifying the microclimates of already-existing university plazas.

scholarly journals The Influence of Sky View Factor on Daytime and Nighttime Urban Land Surface Temperature in Different Spatial-Temporal Scales: A Case Study of Beijing

2021 ◽  
Vol 13 (20) ◽  
pp. 4117
Author(s):  
Qiang Chen ◽  
Qianhao Cheng ◽  
Yunhao Chen ◽  
Kangning Li ◽  
Dandan Wang ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Thermal Environment ◽  
Experimental Results ◽  
View Factor ◽  
Temporal Scales ◽  
Building Height ◽  
Sky View Factor ◽  
The Impact

Urban building morphology has a significant impact on the urban thermal environment (UTE). The sky view factor (SVF) is an important structure index of buildings and combines height and density attributes. These factors have impact on the land surface temperature (LST). Thus, it is crucial to analyze the relationship between SVF and LST in different spatial-temporal scales. Therefore, we tried to use a building vector database to calculate the SVF, and we used remote sensing thermal infrared band to retrieve LST. Then, we analyzed the influence between SVF and LST in different spatial and temporal scales, and we analyzed the seasonal variation, day–night variation, and the impact of building height and density of the SVF–LST relationship. We selected the core built-up area of Beijing as the study area and analyzed the SVF–LST relationship in four periods in 2018. The temporal experimental results indicated that LST is higher in the obscured areas than in the open areas at nighttime. In winter, the maximum mean LST is in the open areas. The spatial experimental results indicate that the SVF and LST relationship is different in the low SVF region, with 30 m and 90 m pixel scale in the daytime. This may be the shadow cooling effect around the buildings. In addition, we discussed the effects of building height and shading on the SVF–LST relationship, and the experimental results show that the average shading ratio is the largest at 0.38 in the mid-rise building area in winter.

Tree planting indices and their effects on summer park thermal environment: A case study of a subtropical satellite city, China

2020 ◽  
pp. 1420326X2097761
Author(s):  
Wei Guo ◽  
Bin Cheng ◽  
Chunlu Wang ◽  
Xinyu Tang
Keyword(s):  
Leaf Area Index ◽  
Leaf Area ◽  
Thermal Environment ◽  
Urban Forestry ◽  
Urban Environments ◽  
Tree Planting ◽  
View Factor ◽  
Radiation Level ◽  
Area Index ◽  
Sky View Factor

Urban residents are suffering from serious thermal stress resulting from urban heat island and global warming. Investigators have explored several methods to address this issue. Vegetation, especially trees, were found to play a vital part in urban environments. It produces a cooling effect by reducing temperature and radiation levels. To find thermal performances of trees in detail, this study physically measured two urban parks during August 2019 in a satellite city of China regarding their thermal environments relevant to tree planting indices. There were three planting indices used, sky view factor, leaf area index and enclosure area. Through associating them with thermal indicators by linear regression, all of the indices were confirmed to have significant thermal effects. Every 0.1 increase in sky view factor resulted in an increase of 1°C air temperature, 0.16 m/s air velocity, 40 W/m2 solar radiation level and 1.6°C mean radiant temperature. Same effects were found in nearly 0.4 leaf area index decrease and approximately 20 m2 enclosure area increase. These results provide very optimistic directions for future urban forestry planning and landscaping.

scholarly journals Effects of Roadside Trees and Road Orientation on Thermal Environment in a Tropical City

2020 ◽  
Vol 12 (3) ◽  
pp. 1053 ◽  
Author(s):  
Sheikh Ahmad Zaki ◽  
Hai Jian Toh ◽  
Fitri Yakub ◽  
Ahmad Shakir Mohd Saudi ◽  
Jorge Alfredo Ardila-Rey ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Air Temperature ◽  
Thermal Environment ◽  
Absolute Humidity ◽  
Field Measurements ◽  
View Factor ◽  
Physiological Equivalent Temperature ◽  
Thermal Environments ◽  
Outdoor Thermal Environment ◽  
Tropical Cities

Emerging tropical cities are experiencing rapid population growth and development, which can greatly affect the thermal environments. The effects of roadside trees and road orientation on the outdoor thermal environment were investigated on four different roads in Kuala Lumpur, Malaysia. Field measurements were conducted to assess outdoor thermal environments, where the selection of sites was based on different roadside tree morphological features and road orientations. Outdoor air temperature (Ta), relative humidity (RH), globe temperature (Tg), wind speed (WS), and wind direction (WD) were measured. Absolute humidity (AH) was estimated based on relative humidity and air temperature. Planting dense canopy trees with an average sky view factor (SVF) of 0.07 reduced the mean radiant temperature (Tmrt) by 35% and the physiological equivalent temperature (PET) by 25%. East–West (E–W) and Northwest–Southeast (NW–SE) oriented roads had high PET values of 41 °C and 43 °C, respectively. North–South (N–S) and Northeast–Southwest (NE–SW) orientated roads had lower PET values (37 °C), providing improved outdoor microclimate. Roadside trees provided greater cooling potential in E–W and NW–SE oriented roads. The findings are useful for urban road design in tropical cities in order to improve the outdoor thermal environment and pedestrian comfort.

scholarly journals Analyzing the Effect of Water Body on the Thermal Environment and Comfort at Indoor and Outdoor Spaces in Tropical University Campus

2021 ◽  
Vol 12 (10) ◽  
pp. 282-288
Author(s):  
Farhadur Reza ◽  
◽  
Shoichi Kojima ◽  
Wataru Ando
Keyword(s):  
Thermal Comfort ◽  
Thermal Environment ◽  
Outdoor Thermal Comfort ◽  
University Campus ◽  
Clothing Insulation ◽  
Comfort Index ◽  
Outdoor Spaces ◽  
Globe Temperature ◽  
And Performance ◽  
University Spaces

Water bodies play a significant role in its surrounding thermal environment. Thermal comfort in university spaces is critical that affects the students’ health and performance as well as the staffs. This study investigated thermal environment and comfort near lakeside and non-lakeside tropical university spaces. Standard Effective Temperature (SET*) have been calculated using recorded air temperature, relative humidity, globe temperature, air velocity, clothing insulation and metabolic rate to evaluate the thermal comfort in outdoor and indoor spaces. The effects of weather parameters have been clearly visible on the comfort index. The calculated SET* values indicate that the outdoor thermal comfort near a lake is much closer to the standard comfort zone than non-lakeside outdoor space. In the case of indoor thermal comfort, however, slightly a different scenario has been observed. To achieve the desirable indoor thermal environment, some design considerations are recommended based on findings.

scholarly journals In-situ Measurement of Pedestrian Outdoor Thermal Comfort in Universities Campus of Malaysia

2019 ◽  
Author(s):  
Nurnida Elmira Othman ◽  
Sheikh Ahmad Zaki ◽  
Nurul Huda Ahmad ◽  
Azli Razak
Keyword(s):  
Thermal Comfort ◽  
Field Measurement ◽  
Thermal Sensation ◽  
Outdoor Thermal Comfort ◽  
View Factor ◽  
Thermal Preference ◽  
Equivalent Temperature ◽  
Physiological Equivalent Temperature ◽  
Sky View Factor

The present study is intended to evaluate an outdoor thermal comfort at two universities campus in Malaysia. Field measurement and questionnaire survey were conducted simultaneously to assess the microclimatic condition and pedestrian thermal sensation. A total of 3033 samples were collected at seven different sky view factor (SVF) values that range from 0.2 to 0.9. The physiological equivalent temperature (PET) was estimated to evaluate outdoor thermal comfort. It was observed that at a highly shaded area (SVF < 0.35) the respondent’s thermal sensation vote (TSV) are neutral (> 25%), acceptable for thermal acceptance vote (TAV) (> 50%) and no change (> 50%) for thermal preference vote (TPV). For moderate shaded (0.35 ≤ SVF ≤ 0.70) TSV was voted as hot (> 25%), acceptable for TAV (40%), and prefer slightly cooler for TPV (>50%). For less shaded area (0.70 < SVF ≤ 1), TSV was voted as hot and very hot (> 25%), acceptable for TAV (>40%) and prefer slightly cooler for TPV (> 40%). Moreover, the PET value increases simultaneously with the increase of SVF. Results thus suggest that at any given activities such as sitting, walking, and standing also caused effects slightly on the way people thermally perceive it during the on-campus daytime.

Analysis of urban thermal environments based on the perception and simulation of the microclimate in the historic city of Tlemcen

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wafa Ghaffour ◽  
Mohammed Nabil Ouissi ◽  
Marc André Velay Dabat
Keyword(s):  
Urban Form ◽  
Thermal Environment ◽  
Thermal Conditions ◽  
Width Ratio ◽  
Subjective Perception ◽  
View Factor ◽  
Content Type ◽  
Outdoor Spaces ◽  
The Impact ◽  
The City

PurposeThe preservation of historic urban centres prevents anarchic development of the city and ensures a harmonious evolution of the urban form. It also improves the quality of life in the context of climate and environmental change. Morphological and geometric indicators of the urban fabric are key parameters in the formation of external microclimates. They provide a positive effect on the thermal comfort of pedestrians. The objective of this work is to study the impact of the site morphology on the external microclimate and to understand the relationship between the subjective perception and the objective quantification of the thermal environment. The result of this study has allowed us to propose solutions for the creation of a microclimate favourable to the appropriation of outdoor spaces. The authors finally propose guidelines for the design and rehabilitation of the historic site based on the establishment of links between the site's configuration, microclimatic conditions and users' perceptions.Design/methodology/approachPart of this study included the analysis of the microclimate of the historic “Bab El Hadid” district of the City of Tlemcen, by developing a questionnaire survey and a numerical simulation validated by measurements of the microclimate the authors made on site. To complete this task, the authors applied the Envi-met 4.1 model during the coldest month of the winter and the hottest month of the summer. Urban parameters are represented at different measurement points characterised by a variability of the sky view factor (SVF).FindingsThe results presented in terms of average expected the predicted mean vote (PMV) voting, solar access and air temperature. They show that thermal conditions are directly related to the SVF, the height/width ratio (H/L) of streets as well as the orientation of urban canyons. The points located in the streets facing North–South, present an acceptable performance. Streets shaded by trees with a canyon aspect ratio of between 1.18 and 1.70 reduce heat stress in outdoor spaces. The PMV models discussed provide information on the most appropriate locations for pedestrians. The authors have proposed urban orientations that could limit unfavourable conditions in outdoor spaces. They are useful for architects and urban planners in the design and rehabilitation of historic centres.Originality/valueIn Tlemcen, the microclimate is not taken into account in the design and rehabilitation of urban fabrics. For this specific purpose, the authors want to stress in the research the importance of safeguarding urban heritage through the renewal of the old city and the bioclimatic rehabilitation of its urban spaces.

Measurement and Analysis of Summer Outdoor Thermal Environment of Campus Open Space in Guangzhou

2011 ◽  
Vol 121-126 ◽  
pp. 4680-4684
Author(s):  
Guang Chen ◽  
Li Hua Zhao ◽  
Qiong Li
Keyword(s):  
Energy Saving ◽  
Open Space ◽  
Thermal Environment ◽  
Great Influence ◽  
View Factor ◽  
Environment Design ◽  
Sky View Factor ◽  
Hot Environment ◽  
Outdoor Thermal Environment ◽  
Measurement And Analysis

Open space is an important part of Campus, also has an important influence to the thermal environment of campus. The measurement of summer outdoor thermal environment of campus open space showed that: the piloti can effectively improve the thermal environment in hot summer; underlying surface materials, sky view factor has a great influence on the outdoor thermal environment. Using appropriate surface structure, increasing piloti and increasing square shading are suggested as outdoor thermal environment optimizing measures based the measure results. Advices were given for hot environment design and passive energy saving design

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 The importance of city trees for reducing net rainfall: comparing measurements and simulations

2018 ◽  
Author(s):  
Vincent Smets ◽  
Charlotte Wirion ◽  
Willy Bauwens ◽  
Martin Hermy ◽  
Ben Somers ◽  
...  
Keyword(s):  
Regression Analysis ◽  
Urban Environment ◽  
Urban Trees ◽  
University Campus ◽  
Area Index ◽  
Rainfall Events ◽  
Norway Maple ◽  
Mediterranean Regions

Abstract. An in-situ tree interception experiment was conducted to determine the hydrological impact of a solitary standing Norway maple and small-leaved lime in an urban environment. During the two-year experiment, rainfall data was collected and divided into interception, throughfall and stemflow. With approximately 38 % of the gross precipitation intercepted by both trees, the interception storage was higher than for similar studies done in Mediterranean regions. A regression analyses for the Norway maple found rainfall duration, rainfall amount and the tree's leaf area index to be the most important variables influencing interception storage. The regression analysis and the tree interception models by Gash and Rutter, as well as an adapted version of the Water and Energy Transfer between Soil, Plants and Atmosphere model (WetSpa), were tested for their accuracy in modelling the measured interception storage. The models in general overestimated interception storage for small interception events ( interception storage). The regression analysis wasn't stable throughout seasons, event sizes and trees making it unsuitable for generic use. The method of Gash slightly overperformed WetSpa and Rutter for all events throughout seasons and trees. However, WetSpa showed a better performance for rainfall events > 10 mm. A scenario analysis, featuring the construction of student houses on a university campus, demonstrated the potential of urban trees to retain rainfall water. Even though trees alone could not restore the natural hydrological balance, they could partly mitigate the increased runoff volume and peak discharge caused by sealing of the natural surface through decreasing the net rainfall that reaches the ground. This study highlights the role of solitary trees in an urban environment where natural hydrological processes are severely altered.

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