Evaluation of tree shade effectiveness and its renewal strategy in typical historic districts: A case study in Harbin, China

2021 ◽  
pp. 239980832110296
Author(s):  
Guanghao Li ◽  
Nan He ◽  
Changhong Zhan
Keyword(s):  
Urban Form ◽  
Urban Areas ◽  
Thermal Environment ◽  
View Factor ◽  
Street Canyons ◽  
Historic Districts ◽  
Planning And Design ◽  
Important Means ◽  
Strategic Support

China’s rapid and extraordinary urbanisation has resulted in a dichotomy between the urban form of historic districts and that of new urban areas. Unlike the new planning of new urban areas, the optimisation of the thermal environment in historic districts is achieved through an important means of regulating the shading effectiveness of trees in street canyons, without destruction of current buildings in existing districts. In this paper, the sky view factor, an index for evaluating the shading capacity of street canyons, is used to calculate the shading efficiency of trees and reveal their influence mechanism by using a convolutional neural network (SegNet) to segment the Baidu street view images. The results show that: (1) tree shading in Harbin’s historic districts has a significant impact on the thermal environment of street canyons, with an average shade effectiveness of 56.3%; (2) based on geospatial autocorrelation analysis and a typological reconstruction of street canyons, the study reveals that tree shading has significant spatial aggregation characteristics in historic districts and proposes guidelines for the planning and design of different types of street canyon trees. The study provides important data and strategic support for optimising the thermal environment of urban historic districts in Northeast China.

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.

Exploration on Traditional Courtyard Micro-Climate Characteristics and Improvement Method - Case Study of No. 6 Courtyard of Chang'anxue Alley in Xi'an Sanxuejie Historic District

2013 ◽  
Vol 357-360 ◽  
pp. 1918-1927 ◽  
Author(s):  
Ruo Bing Fan ◽  
Xiao Ming Li
Keyword(s):  
Sustainable Development ◽  
Thermal Environment ◽  
Urban Expansion ◽  
Historic District ◽  
Climate Conditions ◽  
Historic Districts ◽  
Improvement Method ◽  
New Perspective

Xian Sanxuejie district is a typical historic district of the city. Presently this type of traditional districts is surrounded by many modern buildings due to the rapid urban expansion. The historic districts are facing problems of poor courtyard micro-climate conditions and low living level, which has become the bottleneck of historic districts sustainable development. This paper studies thermal environment, luminous environment, solar environment and wind environment from a new perspective using Ecotect building environment analyzing software. The author explores micro-climate improving method suitable for traditional courtyard in order to promote micro-climate quality of historic district and to improve the comfort of local residences. The purpose is to achieve sustainable development of historic districts.

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.

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 Urban form and vacant shops: can one explain the other? – a case study in Portugal

2017 ◽  
Author(s):  
Miguel Saraiva ◽  
Teresa Sá Marques ◽  
Paulo Pinho
Keyword(s):  
Urban Form ◽  
Urban Areas ◽  
Positive Association ◽  
Urban Morphology ◽  
Negative Effects ◽  
Economic Market ◽  
New Developments ◽  
Morphological Variables ◽  
The City

Shopping is much more than a wealth-generator in post-modern societies; it is intrinsically linked with the way people experience the city and an indivisible part of their day-to-day social experiences. Consequently, the literature has gradually recognized that commercial geographies are not just a consequence of economic market logics. It has been proven that there is a relationship between store-types and urban morphology, and that commerce is an important catalyst for urban regeneration and revitalization. Thus, the urban form can also be a cause for the lack of success of a shop. The amount of vacant shops has been signaled as an important problem in urban areas, affecting the structure and the identity of neighborhoods, and reflects the negative effects of the economic-crisis. Strategies to overcome this problem are usually economically-oriented and fail to capitalize on the new-found relationships between store-success and urban morphology. Thus this research wishes to test whether there are indeed correlations between specific morphological features and the existence of vacant shops, and consequently to propose how changes in the urban environment can contribute to overcome, and even prevent, such cases. The geographical distribution of vacant shops in a sample of Portuguese cities was set against morphological variables such as building age or centrality in the network (Space Syntax). Positive association was found, for example, between new developments and vacant shops, questioning the need for more store space in certain areas; and, particularly outside central neighborhoods, between open shops and high ‘choice’ (rather than high ‘integration’) axes.

scholarly journals Sky View Factors from Synthetic Fisheye Photos for Thermal Comfort Routing—A Case Study in Phoenix, Arizona

2017 ◽  
Vol 2 (1) ◽  
pp. 19-30 ◽  
Author(s):  
Ariane Middel ◽  
Jonas Lukasczyk ◽  
Ross Maciejewski
Keyword(s):  
Thermal Comfort ◽  
Urban Form ◽  
Urban Areas ◽  
Meteorological Data ◽  
Routing Algorithm ◽  
Google Earth ◽  
Urban Environments ◽  
Tree Planting ◽  
Outdoor Thermal Comfort ◽  
View Factor

The Sky View Factor (SVF) is a dimension-reduced representation of urban form and one of the major variables in radiation models that estimate outdoor thermal comfort. Common ways of retrieving SVFs in urban environments include capturing fisheye photographs or creating a digital 3D city or elevation model of the environment. Such techniques have previously been limited due to a lack of imagery or lack of full scale detailed models of urban areas. We developed a web based tool that automatically generates synthetic hemispherical fisheye views from Google Earth at arbitrary spatial resolution and calculates the corresponding SVFs through equiangular projection. SVF results were validated using Google Maps Street View and compared to results from other SVF calculation tools. We generated 5-meter resolution SVF maps for two neighborhoods in Phoenix, Arizona to illustrate fine-scale variations of intra-urban horizon limitations due to urban form and vegetation. To demonstrate the utility of our synthetic fisheye approach for heat stress applications, we automated a radiation model to generate outdoor thermal comfort maps for Arizona State University’s Tempe campus for a hot summer day using synthetic fisheye photos and on-site meteorological data. Model output was tested against mobile transect measurements of the six-directional radiant flux density. Based on the thermal comfort maps, we implemented a pedestrian routing algorithm that is optimized for distance and thermal comfort preferences. Our synthetic fisheye approach can help planners assess urban design and tree planting strategies to maximize thermal comfort outcomes and can support heat hazard mitigation in urban areas.

scholarly journals DO POST-SOCIALIST URBAN AREAS MAINTAIN THEIR SUSTAINABLE COMPACT FORM? ROMANIAN URBAN AREAS AS CASE STUDY

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Simona Raluca GRĂDINARU ◽  
Cristian Ioan IOJĂ ◽  
Ileana PĂTRU-STUPARIU
Keyword(s):  
Urban Form ◽  
Urban Areas ◽  
Planning System ◽  
Compact Form ◽  
The European Union ◽  
Housing Provision ◽  
The Public ◽  
Development Level ◽  
Development Trajectories

The compact city is regarded as an important concept in promoting sustainable development, especially within the European Union. The socialist urban planning system maintained a high compactness of the urban areas through almost exclusive predominance of the public sector in housing provision, and ideological nature of the planning strategies. After the 1990’s, the administrative decentralization allowed local authorities to adopt particular urban development strategies. However, development was directly influenced by the importance of the urban administrative centre. The aim of the paper is to determine if post-socialist urban areas maintained their compact urban form or they encountered different evolution trajectories. We determined the type of changes by calculating urban form indicators at two time moments: 1990 and 2006. Furthermore, the two-way repeated-measurement ANOVA was used to identify significant changes, and to assess the effect of the development level of the urban area on the variance of form indicators. The results show that Romanian post-socialist urban areas either shifted from the compact form, "inherited" after the collapse of socialism, to more dispersed patterns, either expanded in a compact manner. Moreover, as development level got higher, urban areas were more likely to be affected by suburbanization and periurbanization. In order to respond to these challenges, new instruments such as setting of metropolitan areas or spatial framework plans could be used. Furthermore, planning should be adapted to local circumstances and to the different development trajectories of big and mid-sized urban areas.

A Probe into Localized Urban Design Approach – Case Study of Design for Guangzhou International Financial City (GIFC)

2013 ◽  
Vol 368-370 ◽  
pp. 160-164
Author(s):  
Yan Fei
Keyword(s):  
Public Space ◽  
Urban Design ◽  
Urban Areas ◽  
Ecological Design ◽  
Space System ◽  
The Public ◽  
Planning And Design ◽  
Design Idea ◽  
Design Proposal

Urban design for high-intensity central urban areas often ends up with the conglomeration of high-rises, while these areas are then faced with the question as how reasonable planning and design approaches could be employed to reflect the green and ecological design idea, optimize the spatial and environmental quality and carry on the local traditional culture and features. To respond, this paper conducts a case study of the GIFC urban design proposal, and further explores the green and ecological design approaches with the local Lingnan characteristics from the perspectives of the macro-level ecological pattern, the spatial order as well as the establishment of the public space system, with the intent to offer some reference for the development of new urban areas.

scholarly journals Study on the Effect of Streets’ Space Forms on Campus Microclimate in the Severe Cold Region of China—Case Study of a University Campus in Daqing City

2020 ◽  
Vol 17 (22) ◽  
pp. 8389
Author(s):  
Hong Jin ◽  
Liang Qiao ◽  
Peng Cui
Keyword(s):  
Wind Speed ◽  
Air Temperature ◽  
Urban Areas ◽  
Thermal Environment ◽  
Heat Convection ◽  
Heat Radiation ◽  
View Factor ◽  
University Campus ◽  
Human Comfort ◽  
Open Type

In urban areas, local microclimate is influenced by architectural forms, which will in turn affect human comfort. Taking Daqing as an example, this article studies the microclimate of a university campus in the severe cold area in China. Based on the space features of the streets, we categorize the streets into three types: open type, semi-open type, and street-entry type. Through analysis, this article researches microclimates of the three kinds of streets, the influence of building heating on the surrounding thermal environment, the relationship between streets’ morphology features and microclimate and human comfort (physiological equivalent temperature, PET). By study and analysis, we have the following findings: for open-type streets, the average globe temperatures of streets with different orientations can reach 1.3 °C in winter because of the influence of sidewalk trees. For semi-open-type streets, streets temperature is under the influence of the locating directions of buildings. The maximum air temperature difference among streets with different building arrangements reaches 2.1 °C in winter. For street-entry-type streets, the height–width ratios and orientations of streets are related to the continuity degree of the street interfaces. The building interface acts as a heating element and affect the surrounding thermal environment by heat convection and heat radiation. Analysis demonstrates that heat convection has a more obvious effect on rising surrounding temperature than heat radiation. Buildings with higher heat radiation witness higher globe temperature. For street-entry-type streets and semi-open-type streets, the SVF (sky view factor) and L/C (plane opening rate) of streets are negatively correlated with temperature and PET, but positively correlated with wind speed. If the SVF increases 0.1, the air temperature will reduce 0.1 °C, the wind speed will increase 0.19 m/s, and the PET will reduce 0.7 °C.

Sign in / Sign up

Export Citation Format

Share Document