POSTER 2: UCD - Impact of urban forms on comfort and ventilation
Climatically Adapted Piloti Arrangement and Ratio of Residential Blocks in a Subtropical Climate City
1Wuhan University, China; 2Tohoku University, Japan
Piloti is a method can adapt to the impacts of inevitable UHI (urban heat island). It can provide shaded-space as well as trees, improve the surrounding wind velocity and alleviate the thermal comfort of human beings. In addition, piloti does not produce water vapor so that the humidity will not be raised. In this paper, the coupled simulations for outdoor wind and thermal environment of residential blocks in Wuhan were carried out. Through comparing the results of basic case and four cases with different piloti arrangements, it was clarified that piloti set in the two ends of building is the optimal piloti arrangement. Then the relationships between piloti ratio and outdoor thermal environment (wind, MRT, SET*) in summer were investigated based on the optimal piloti arrangement. Finally, climatically adapted piloti arrangement and ratio were proposed for design of residential area.
Study on the Green Strategies of Chinese “Neo-vernacular Architecture” Design
Huazhong Unversity of Science and Technology, China, People's Republic of
These years, with the green building research rising, the rational mode of human beings and nature in China traditional architecture, which contains rich experience about ecological design, should be re-considered.This article demonstrates an integrated ecosystem approach in the whole process of neo-vernacular architecture complexes planning and single unit design. We elucidate this method by examining the real design project called “Xijie Neo-vernacular Architecture Design”, a national bid we just finished, from Wuhan, China. A series of elements, which include not only formalism, natural surroundings, native cultural characters, but also climate strategies and construction techniques, such as cold passage, form shading, patio ventilation, thermal insulation material, permeable pavement, are carefully taken care of. Hope this article can make help to ecological building design.
Microclimate Regulation by Trees in a Subtropical High-Density Urban Environment during Sunny and Cloudy Weather
The Chinese University of Hong Kong, Hong Kong S.A.R. (China)
The hot, humid summers of subtropical Hong Kong cause thermal discomfort, which is further intensified by the urban heat island (UHI) effect in heavily built-up areas (Goggins et al., 2012). Urban greenery has been proposed as a mechanism for microclimate regulation, yet the thermal impact of such greenery in the high-density urban environment has seldom been mentioned in the literature (Wang and Chen, 2005). This study reviews outdoor thermal comfort criteria in the hot-humid subtropics. It then evaluates the environmental effects of trees in urban areas with varying sky view factors (SVF), based on the comfort criteria. The role of tree crown density in forming a comfortable microclimate is discussed in the context of urban morphology. These effects were studied in the early afternoon under typical summer cloudy weather, and under fine weather with intense solar radiation, to address the 'prevailing' and 'critical' issues (Ng, 2012) in daytime comfort and UHI mitigation.
On-site measurements were conducted in urban areas of Hong Kong with SVF ranging from 0.2 to 0.8. At each site, several environmental factors were measured under tree canopies and at nearby exposed reference points: air temperature, relative humidity, wind speed, downward radiation, and globe temperature. Mean radiant temperature (Tmrt), calculated using the measured data, was used as comprehensive microclimate indicator (Thorsson et al., 2007). Measurements were taken in sunny, partially cloudy, and overcast weather, and the observed data revealed that the shading effect of urban trees was strongly related to SVF. On cloudy afternoons, Tmrt was 15C lower under a tree canopy than at exposed points at site of 0.8 SVF; at a site of 0.2 SVF, the difference in Tmrt was reduced to 3.5C. The tree effects were more profound on sunny days, when the variation in Tmrt was 30C and 25C, respectively, for the two SVFs. It can be seen from the data that thermal behaviors of urban trees under low and high SVF were more diverse during cloudy weather. In heavily built-up areas with low SVF of 0.2-0.3, urban trees can provide a "comfortable microclimate" (Forwood et al., 2000; Ng and Cheng, 2012) by maintaining the Tmrt at around 33C in the early afternoon. Outside the canopy, Tmrt reached 37C on cloudy days and exceeded 60C on hot, clear days.
Using the measured data, the vegetation scheme of the three-dimensional microclimate model ENVI-met was validated. As the measurements showed, the solar transmission of the tree crowns, and the microclimate under the canopy, were strongly dependent on the density of tree crown. A parametric study was conducted, using ENVI-met to investigate the influence of leaf area density (LAD) under different SVFs on sunny and cloudy days. The result demonstrated that with an average LAD around 1.0, trees can cool the air by 1C and the ground surface by 10C, and lower the Tmrt to comfortable level. Simulation results also pointed out that to avoid overheating in hot, clear weather, it is necessary to consider the summer sun angle in the subtropics when designing greenery plans for high-density districts.
The study demonstrated that it is of great significance to plant trees in high-density urban areas with low SVF. A 4C temperature rise was reported as UHI effect in heavily built areas of Hong Kong (Siu, 2013). Trees of appropriate canopy density can provide a comfortable microclimate in these districts. At the same time, the net environmental impact of urban trees was found SVF-related, especially under cloudy weather. Therefore, to address the issue of summer outdoor comfort, building-morphology-based strategy is essential for urban greenery design in Hong Kong. Based on the finding, site-specific tree planning suggestions responding to urban morphology and subtropical sun angle are summarized in the paper.
PROPOSITION OF AN INDEX QUANTIFYING THE AMOUNT OF VEGETATED FRACTION NEEDED FOR AIR TEMPERATURE CHANGES IN URBAN LOCATIONS
UTFPR, Brazil, Germany
Vegetation can produce measurable effects on the thermal field of urban spaces. In view of thermal inadequacies in outdoor spaces, there is a need for projects and urban design strategies which consider the use of vegetation as strategic element for the creation of thermal comfort conditions in open spaces. In this sense, the relevance of this study is the proposition of an index which estimates the amount of vegetated fraction needed to reduce the air temperature in urban areas. The index was developed for the city of Curitiba, in southern Brazil (25°31’ S, 49°11’ W, mean elevation around 935 m a.m.s.l. and with subtropical highland climate Cfb, according to Köppen’s climate classification), specifically for its central arteries such as Avenida Sete de Setembro and Avenida Linha Verde. The study combines field microclimatic measurements and computer simulations with the ENVI-met model, which allowed the comparison of current and alternative scenarios. All simulations have been carried out for summer conditions. The thermal comfort indices Physiological Equivalent Temperature (PET) and Universal Thermal Climate Index (UTCI) were used to assess levels of thermal stress at the pedestrian level. In general, it was observed that the insertion of green areas (particularly under dense canopy) could slightly reduce daytime air temperature in urban areas having a more substantial impact on changes in heat stress categories. The proposed index (ratio between the increase of vegetated over built-up area) may explain the reduction of mean air temperature by 83.1%. From its application, it can be concluded that a 1°C reduction in air temperature should be expected for an increase of 49% in vegetated fraction. The importance of the index (and the proposed methodology behind it) lies in the possibility of its use in urban planning and climate-responsive urban design.
Study on the Cooling Effects of Green Spaces for Improving the Outdoor Thermal Environment in the High-density Cities: A Case Study of Macau Peninsula
School of Architecture, The Chinese University of Hong Kong, Hong Kong S.A.R. (China)
The thermal environment have several effects on people who in the outdoor spaces. For high-density urban living environment such as Macau, green spaces can improve thermal comfort in outdoor urban spaces in moderate climates, which have been proven to significantly mitigate urban heat islands (UHI) and decrease ambient air temperature created by urbanization. However, the environmental benefits of cooling provided by urban green spaces have rarely been measured. This study focuses on the importance of green spaces as a potential method for use in reducing ambient air temperatures and for passive cooling effects, especially at a pedestrian level.
In this study, Macau Peninsula is chosen to carry out a case study, which is one of high-density urban areas and need local planners to make climate change adaptation in urban construction. These greening modification methods were investigated regarding their local cooling effect. Two approaches are presented in the study, including the on-site measurement and numerical ENVI-met simulation models. Measurements of weather parameters (temperature, wind speed, relative humidity, solar and infrared radiation) were carried out along the selected typical paths, starting from inside the green spaces to surrounding streets with different orientations and solar exposure. The parametric studies then employed the model ENVI-met, verified using field measurements, to simulate numerical cases with different combinations of factors.
It was found that physiological equivalent temperature (PET) in urban green spaces on average was lower than surrounding areas, either in the sun or in the shade during the hottest period of the day in Macau Peninsula. These differences were higher in hotter days and particularly related to the mean radiant temperature (Tmrt). In addition, the weather conditions, the sun exposure, the low wind speed and the urban geometry are the potential factors for these differences. Besides, the study reveals that thermal variance between green spaces was mainly influenced by tree canopy cover and upwind vegetation cover, not for the size of green spaces. The study allows urban planners to identity more precisely the methods, principles and policies of green space planning for improving outdoor thermal environment in high-density areas.
Influence of different urban configurations on human thermal conditions in a typical subtropical coast city: case of Santos, São Paulo
1State University of Campinas, Brazil; 2Albert-Ludwigs-University Freiburg, Germany
Urban design parameters as buildings’ height and street orientations can affects human thermal comfort conditions in subtropical cities considerably. This study aims to quantify the human thermal conditions at pedestrian level and develop strategies to adapt the urban climate. The urban configuration of Santos can be represented by typical urban street, a long urban park in front the seaside and urban trees canal. The simulations have been done using a long-term meteorological data from Santos airport for the period 2002 to 2012. The simulations were conducted with the radiation and bioclimate model RayMan. The human thermal conditions were assessed in terms of mean radiant (Tmrt) and physiologically equivalent (PET) temperatures. PET values, higher as 41°C, are observed to prevail during the summer’s afternoons especially in the east-west oriented streets with height and width ratio (H/W) less than 0.5. In streets oriented east-west, façades of buildings’ height of 45 m provide shadow effect and improve thermal heat stress. The densification within urban grid can modify the urban ventilation and consequently thermal conditions. The management of green areas is recommended to promote shade on pedestrian ways and façades and improve human thermal bioclimate controlling. The method and results can be applied by architects and urban planning interested in developing guidelines for urban climate including climate change.
Variability of longwave radiation in a midsize city: Experiments in free spaces in São Carlos-SP.
1University of São Paulo, Brazil; 2University of São Paulo, Brazil; 3University of São Paulo, Brazil; 4University of São Paulo, Brazil
The energy balance and the radiative flux produced in urban areas are not objects of many studies in Brazil. This research aimed to determine the variability of flows of energy in long waves in a Tropical midsize city. The methodology is based on the use of an infrared digital thermometer fixed on a tripod, with the manual measurement of cardinal points and the side slopes of -10º, 0°, 10º, 25º, and 35º, in various classifications of urban land use defined by the Laboratory Quadro do Paisagismo do Brazil - QUAPÁ. Has been made in São Carlos-SP eleven field trials representative climatic episodes in winter and summer. The polar invasions in the city of study, in phase of domain, imposes the initial conditions of weather types with thermal values surface over mild compared with the tropicalized phase. In field trials the highest temperatures were recorded for the angles -10 ° and 0 ° to the approximate height of the pedestrian level. The thermal patterns observed in local were corresponding to some classifications and not to others, because they depend on multi scalar factors as advection, intraurban layer, flows sensible heat and latent heat.
Green infrastructure enhancement in Glasgow: A proposal based on Local Climate Zone evaluation of urban morphology in a shrinking city
1Glasgow Caledonian University, United Kingdom; 2University of Rio de Janeiro, Brazil; 3University of Salento, Italy
Local warming continues to grow in Glasgow, UK, even though the urban growth in the city has long peaked. The contribution of urban morphology to generate local heat islands is currently net positive but is expected to be negative as the background climate continues to warm. Reversible strategies that are able to tackle the negative consequences of urban warming are needed in shrinking cities to anticipate and accommodate future regeneration possibilities. Green infrastructure offers one such possibility but urban planning authorities need evidence-based proposals to promote such approaches in their climate change adaptation plans.
In this paper we present a relatively less data-intense method to classify local climate zones (LCZ) and evaluate the effectiveness of green infrastructure options in tackling the likely overheating problem in cold climate urban agglomerations such as the Glasgow Clyde Valley (GCV) region. LCZ classification uses LIDAR data available with local authorities, based on the typology developed by Stewart and Oke (2012). Built cover/green cover and land use classes were used to identify LCZ classes, which in turn were used to cluster areas likely to exhibit similar warming trends locally. This helped to identify likely problem areas (‘hot spots’), a sub-set of which were then modelled to quantify the effect of green cover options (both increase and reduction in green cover) as well as building density options.
Results indicate green infrastructure could play a significant role in mitigating the urban overheating expected under a warming climate in the Glasgow Clyde Valley (GCV) Region. A green cover increase of approximately twenty percent over the present level could eliminate a third to a half of the expected extra urban heat island effect in 2050. This level of increase in green cover could also lead to local reductions in surface temperature by up to 2 deg. C. Over half of the street users would consider such an increase in green cover in the city centre to be thermally acceptable, even under a warm 2050 scenario.
The realisation of green cover could take several approaches and we use the Green Area Ratio Method to propose green infrastructure alternatives for Glasgow city centre. The process adopted here could be used to estimate the overheating problem as well as the effectiveness green infrastructure strategies to overcome them in other similar cities.
Cold and urban design. Challenging Russian cities
Politecnico di Milano, Italy
In the present essay the climate-related issues are for the first time investigated for the Russian cities. This topic has never been widely discussed and therefore has an innovative concern.
The thesis gives an overview of the existing conditions in the northern Russian cities, which is the result of the history of the mastering of Siberia but mainly of the rapid urbanization and industrialization during the 20th century under Soviet regime. This period is considered to be the starting point of the mass construction and typical building design solutions. The appearance of new paradigm of effective, cheap and utilitarian construction was conformable with the socialistic ideology. This race has led to the arisen of numerous new cities across the country, which were all similar as the tweens. The vast areas of Siberia and North were not an exception, since the region has the rich basins of natural resources.
Relation between climate and urban issues requires a comprehensive research in order to provide comfortable microclimate conditions by the means of urban design and architecture. Unfortunately, in the 20th century this was not an issue due to the fast pace of development and is not an issue today in the period of ubiquitous private developments concerned only with the profitable land mastering. Nevertheless, the special attention has to be given to the comfort living conditions on the north, since they are encumbered by the lack of solar radiation, long winter periods, extremely low temperatures and strong winds, excessive snowfalls and lack of vegetation on permafrost.
The aim of the thesis is the understanding of what are the living conditions in the northern cities and what were the processes which have led to the current situation and proposal of regulations, which should be used for planning in the northern cities according to their specificities.
By providing testing of selected samples of typical Soviet urban design solutions with the Karalit SW in different climatic regions the evidence of their typical character as well as the discrepancy to the climate is interpreted in relation to the morphological parameters of the urban fabric. The interpretations of the simulation results are the basis for the author’s proposals and guidelines.
The influence of urban geometry on thermal comfort of public open spaces for Italian climate zones
1Sapienza - University of Rome, Italy; 2Albert Ludwigs University, Freiburg, Italy
The relationship between urban geometry and microclimate is a relevant topic for both urban planning and urban climatology, as it significantly influences the thermal comfort of individuals. Urban geometry has a conflicting seasonal effect on thermal comfort, with a demand for compactness in summer, to secure protection from the sun, and openness in winter, to provide solar access. Therefore, this aspect needs to be addressed by long-term analysis.
We present a numerical study on the effect of urban geometry (building and space proportions) on the thermal comfort of public open spaces in Italy. According to a detailed version of Köppen-Geiger classification, 6 Italian cities were selected as representative for each Italian climate zone: Aosta, Milano, Campobasso, Firenze, Lecce, Catania. Alpine climates were excluded, as they affect no significant urban area.
The assessment of thermal comfort is based on the Physiologically Equivalent Temperature (PET), calculated using the RayMan model. The input for the model are 30 years data on air temperature, vapor pressure, air velocity and cloud cover, with 3-hours resolution, obtained from the meteorological station of each city.
The results of daily median analysis over the year and seasonal frequency analysis indicate that aspect ratio appears to have a stabilizing effect over thermal comfort, more conspicuous in summer than in winter. However, the absolute levels of PET vary according to the climate zone, linking the use of each urban proportion to specific climatic conditions.
Architectural bioclimatic analysis of kashan and presentation
student, Iran, Islamic Republic of technical and vocational rajaeikashan university
Nowadays in construction of cities, consideration of climate's architecture, plays a minor role in architects designing .With considering this issue that for creating comfort condition in the buildings with different usage like residential, businesses and … .
The vital role of compatible architecture with the climate shouldn't be ignored
With the case study of classic architecture (the historical context of kashan) some studies in the field of data information of kashan climate by the use of Gionee diagram has made that with using humidity ,wind ,shadow, radiation and other effective factors in order to reach to comfort in the different seasons of the year. An effort has made to present compatible solution with the climate toward sustainable development some measured should be taken.
Keywords :bioclimatic ,Gionee diagram ,compatible to the climate,kashan
Quantification of thermal bioclimate of Erzurum based on different land uses and thermal band information
1Ataturk University, Turkey; 2Ataturk University, Turkey; 3Ataturk University, Turkey; 4Ataturk University, Turkey
Living environments (urban ecosystems) are deteriorating day by day and the level of human quality of life is decreasing depending on the changes faced in urban areas. Studies on the effects of the changes in urban land use on urban microclimate and the meaning of these changes for urban ecosystems are quite inefficient and superficial in especially Turkey. Over recent years, the quality and quantity of the studies regarding the extents of global warming and its future projection have consistently increased. Subject matter of the study is very hot and important since it deals with the human quality of life. Therefore, it is vitally important to determine how the areas which constitute urban land use classes such as open green spaces, housing and industrial areas, rangelands, agricultural areas etc., may affect urban microclimate.
With the results obtained in the study it can clearly be estimated how much green or open space will be needed in order to create more comfortable and liveable urban environments. After the conduction of the study, obtained results will be able to give the opportunities to calculate precise and strong relationships between the sizes of green areas and their effects on climatic elements instead of the statements taking place in many related studies as “ green areas can affect urban microclimate”. In the city, where heavy air pollution is experienced in winter months, requirements can be determined for the city to have more climatically comfortable conditions and to increase the number of comfortable days if the study is conducted. In addition, the effects of air pollution on climatic elements can be determined in the scope of the study. Outcomes of the study will be a database for the works of local authorities and governorship.
Mill Avenue, Tempe, AZ Downtown Microclimate - an APA-designated Best Street
arizona state university, United States of America
Climate change scenarios for the desert Southwestern United States suggest a warming and drying climate to mid-century. In the state of Arizona, a region labeled the Sun Corridor will experience major urban development in the future. Scenarios raise concerns about summer temperature extremes impacting energy, health, and water use. We address human comfort of a downtown city area of the Phoenix Metropolitan Area – Tempe, Arizona. This city has been noted by the American Planning Association as an excellent example of improving the environment and attracting tourists as well as local citizens. It thus became an interesting “laboratory” to survey, and perhaps a future kind of microclimate to envision, as opposed to the typical urban sprawl type city Phoenix generally represents. Thus, our purpose is to gain knowledge on microclimate and human comfort offered by downtown Tempe. The methods included diurnal weather observations at selected locales, thermographic imaging, analysis of a NASA-funded thermal overflight day and night set of high resolution images, and use of microclimate modeling and human comfort calculations. Overall, as expected for late spring, summer and early fall conditions, we found that urban forms with more compact building spaces act to reduce sun exposure and increase hours of comfort. Some nighttime heat retention was experienced due to decreases in sky view factors, consistent with other urban studies on heat islands. However, due to large diurnal temperature ranges of this desert climate, nighttime PET temperatures normally drop below 30-35oC even in some compact spaces. We also found significant microclimate differences that relate to factors such as the extensive use of misters (to create evaporative cooling, e.g., in open spaces, plazas, outdoor eating places), vegetation lining north-south sidewalks and main street median strip, pavers to enhance reflectance particularly in plazas between buildings, walk-through tunnels from streets to interior court yards, and awnings, arcades, and overhangs along sun-exposed sidewalks. In terms of air flow, we found that even slight increases in ventilation above calm to slightly windy conditions can be quite beneficial to daytime comfort. Phoenix has been labeled the world’s most unsustainable city - a city waiting to burn up (Andrew Ross, 2011; in his book Bird on Fire). The future can be different – downtowns can be re-designed to enhance comfort as well as improve other factors of everyday living.
Summer and winter thermal and comfort conditions inside a vegetated courtyard area of a Mediterranean city (Athens)
1Agricultural university of Athens, Greece; 2Technion-Israel Institute of Technology, Haifa Israel
Appropriately designed open and semi-open spaces may function effectively as positive bioclimatic elements in the urban environment and thus they may be integrated in a sustainable urban design context. Courtyards are common architectural solutions; depending on their detailed design (geometry, vegetation presence and materials), they can be positive or negative climatic elements in the urban environment In the present study the microclimatic and thermal comfort conditions of a vegetated courtyard area located in an urban cluster of the city of Athens (Greece) are estimated and evaluated. In the selected courtyard area, continuous measurements of microclimatic parameters (air temperature, relative humidity, wind speed, net radiation and global solar radiation) were carried out during a summer and also a winter time period. In addition, an urban microclimatic model was used to evaluate combined building and vegetation design scenarios that may improve microclimatic and bioclimatic conditions inside the courtyard and also in the surrounding urban cluster area. The implications of the study’s results on the architectural design for Athens are mainly associated with propositions to have high mass residential buildings with backyard vegetated areas to moderate the extremely high or low air temperature values and to ameliorate, to a certain degree, comfort conditions of occupants.
Study of urban ventilation corridor planning method based on a case study of Guiyang, China
Huazhong University of Science and Technology, China, People's Republic of
In recent years, most of the cities in China are affected by the problem of air pollution, including the capital city Guiyang of Guizhou province of Southwest China. Guiyang has a four-season, monsoon-influenced humid subtropical climate, and it is famous for its mild and pleasant climate and environment. However with the urban development, the pollution of Guiyang becomes more and more serious. To reduce air pollution, improve the outdoor thermal comfort, and save energy consumption, the city council of Guiyang has organized a special project of urban ventilation corridor planning and design in Guiyang area, since October, 2013.
This project aims to improve the wind environment of Guiyang, and then promote the diffusion of pollutants. Firstly, the Weather & Research Forecasting model of WRF is applied to this project to find out the areas and locations with poor wind environment. Secondly, the planners connected all these areas and locations with the existing green area, water system, or traffic network of Guiyang and planned the urban ventilation corridors. According to the environment, natural resources, and weather condition of Guiyang, planners designed 6 first level corridors, 16 second level corridors, and 30 third level corridors basing on the principles of urban ventilation corridor planning of Guiyang, which are reserving the green space, dredging the channels, and controlling the development. Thirdly, WRF is applied to this project once more to evaluate the effect of urban ventilation corridor of Guiyang with the comparison between a case with urban ventilation corridor and a case without that. The simulation results of WRF illustrated that because of the planning of urban ventilation corridor, the winter average wind speed of Guiyang increases 8%, summer average wind speed of Guiyang increases 6%, winter average wind speed of the central city of Guiyang increases 12%, and summer average wind speed of central city of Guiyang increases 9%.
STUDIES BY ASSOCIATING THE URBAN MORPHOLOGY AND THE VENTILATION: RESIDENTIAL VILLAGE OF UFRJ
1UFRJ, Brazil; 2UFF
Urban areas influence and are influenced by local climate, which behaviour interferes on life quality of people and can result in energy consumption increase in the case of intra-urban temperature rise. In Brazil, there seems to be a shortage of microclimatology studies that are directly useable in urban planning and design. The understanding of relations between ventilation dynamics and urban morphology helps us to find configurations of the urban mesh able to mitigate, at least in part, impacts generated by changes in local climate. Federal University of Rio de Janeiro’s – UFRJ – campus, in Fundão Island, is passing through a phase of constant changes and there are plans for new constructions and interventions, according to UFRJ’s Master Plan 2020 (2009), already sketched up. By applying microclimatology studies in UFRJ’s Campus area, more specifically in the Residential Village – VR –, we expect to face a unique opportunity to develop a ground zero study of the ventilation dynamics for that region before large modifications occur. The VR’s starting point was an old construction site of the Rio-Niterói Bridge – the construction begun in 1969 – on the south area of University’s City. This construction site was comprised of 180 residential units and support service facilities to assist workers and their family members, and after the end of construction, many families chose to remain in the region as illegal occupants. Nowadays VR occupies an area of 20 thousand square meters, gathering nearly 2 thousand people in about 350 homes, it’s worth mentioning that the inhabitants were granted legal position of the land, but that they continue to struggle for public service and life quality improvements in the region. The VR is now contemplated on the “University’s Residence Politics” – CIDUNI – of the “University’s City prefecture”. For the ventilation studies the Wind Tunnel based in the Faculty of Architecture and Urbanism – FAU/UFRJ – was used. The air temperature was measured using the transect method, carried in a short time space and under intense insolation. Five stop points were selected, within the VR and this selection, sought to represent the diversity of morphology within the VR, e.g., tree-lined street, narrow street, broad street, open place (square), proximity to the sea. Each point was georeferenced and documented with images obtained through a fish eye lens. From the images, masks solar trajectory maps were generated and the sky view factor was calculated. The region map was taken as basis for building the 3D model tested in the wind tunnel, but the heights and new buildings were observed in situ. Charts with bioclimatic analysis of each point were filled to complement the information and get a closer picture of scenario. The results begins to delineate strategies for climate sensitive design pointing interference in urban morphology appropriate to the area of VR, taking into account not only the position of streets in relation to the prevailing and secondary winds, as well as the barriers in the environment. The close link between urban geometry and outdoor comfort could contribute to planners and designers’ ability to create urban spaces of quality.
Using GIS tools to assess the urban environment influence on the particles concentration variability in Paris
1PMCLab - University Pierre & Marie Curie, Paris, France; 2University Paris Diderot, Sorbonne Paris Cité - UMR CNRS PRODIG, Paris, France
Particles affect public health (respiratory and cardiovascular), increasing morbidity and mortality rate. Currently, they are one of the most important megacities' air pollution problems. Moreover, their concentration, composition and size distribution are spatially highly variable due to different emissions and air mass movements. At the scale of the city, street geometry (orientation, width…), the built-up environment (density, color, materials…) and the green spaces also strongly affect the spatial distribution of pollutant concentrations.
From a GIS analysis, we calculated several geometric parameters chosen to give a fair representation of the Parisian urban space (building density, SVF, street orientation, proportion of green spaces…), taking into account also the topography of the city. To assess outdoor pollution levels on a fine scale, we performed several mobile measurement campaigns of particles concentrations, with low cost sensors as well as certified sensors, for different weather conditions.
In this paper, we highlight and explain the observed spatial variability of particles concentrations by comparing mobile measurements and urban indices. We evidence the strong influence of the geometry of streets and wind. Beyond these results, this presentation allows us to discuss the relevant scale for the pollution phenomenon as well as the representativeness of measurements and interoperability between data points and environment contexts.
Role of Vegetation, urban morphology and building rise in air quality and urban heat island: simulations in five Parisian neighborhoods.
1EIVP, France; 2University of Mons, Belgium
The European heat wave in 2003 has evidenced the vulnerability of cities to a warmer climate. From the 1st to the 20th of august 2003 France experienced an abnormally high death rate of 14 800 people (INVS, 2003). The rate was higher in Paris because of the population density along with the effect of urban heat island, in fact the meteorologist observed a difference of 8°C among the center of Paris and the near country side. As well air pollution is stronger in urban areas and mortality is also related with this phenomenon. Currently, municipalities have to deal with both air pollution and urban heat island. Cities planners usually treat both problems separately, leading to antagonisms measures. For instance, trees shades seem be mitigate UHI, but may increase pollutants concentrations. Canopy trees could indeed induce the stagnation of pollution in some street canyons (Vos, P.E.J., et al., 2012). Therefore, the role of vegetation has to be studied regarding both issues, the benefices couldn’t be always positive. In addition, urban densification is frequently related with UHI; however the development of new surfaces outskirts of large cities increases the effect of severe heat waves unlike what happens in more compact cities (Stone et al., 2010). Therefore, urban densification has to be also evaluated. There is a necessity to find synergetic solutions to treat both UHI and air pollution.
We have identified two parameters that influence UHI and air pollution concentrations: morphology and vegetation. Our study proposes to compare different scenarios for adaptation or protection against UHI and air pollution. Scenarios of adaptation are simulated in five homogeneous neighborhoods in Paris using ENVI-met. For each neighborhood, four scenarios are presented. Amongst others variables, thermal variances as air pollution concentration are simulated, this allowed to treat simultaneously UHI and air pollution dilemma. Specific relations were founded in the five neighborhoods; nevertheless there are still uncertainties. However, our study search to open the debate to compare urban typologies against each other, and finally to match scenarios of climate adaptation in order to have a wider reflection of this urban antagonism.
Analysis of Detailed Air Flows in Urban Areas Using GIS Data and a CFD Model
pukyoung national university, Korea, Republic of (South Korea)
In this study, detailed air flow characteristics in an urban areas were analyzed using GIS data and a computational fluid dynamics (CFD) model. For this, a building construction algorithm optimized for geographic information system (GIS) data with a vector format (Los Angeles region imagery acquisition consortium 2 geographic information system, LARIAC2 GIS) was used. In the LARIAC2 GIS data, building vertices were expressed as latitude and longitude. Using the model buildings constructed by the algorithm as the surface boundary data in the CFD model, we performed numerical simulations for two building‒congested areas in Los Angeles using inflow information provided by California Air Resources Board. Comparing with the inflow, there was a marked difference in wind speed and direction within the target areas, which was mainly caused by the secondarily induced local circulations such as street‒canyon vortices, horse‒shoe vortices, and recirculation zones. In street canyons parallel to the inflow direction, wind speed increased due to a channeling effect and, in street canyons perpendicular to the inflow direction, vertically well developed vortices were induced. In front of a building, a horse‒shoe vortex was developed near the surface and, behind a building, a recirculation zone was developed. Near the surface in the areas where the secondarily induced local circulations, wind speed remarkably increased. Overall, wind direction little (largely) changed at the areas where wind speed largely increased (decreased).