POSTER 8: BPH/UDC - Outdoor microclimate, modelling and link with urban form
Evaluation on the outdoor thermal climate using an integrated urban canopy model and geographic information: a case study in Shenzhen
1School of Municipal and Environmental Engineering, Harbin Institute of Technology, China, People's Republic of; 2State Key Laboratory of Urban Water Resource and Environment, Harbin Institute of Technology, China, People's Republic of; 3Shenzhen Key Laboratory of Urban Planning and Decision Making, Harbin Institute of Technology Shenzhen Graduate School,China, People's Republic of
In order to obtain an accurate evaluation on the outdoor thermal environment of complex urban construction area, the aim of this study is to adopt the multipurpose regional thermal climate prediction model (UDC) to simulate the thermal climate parameters. Considering the International Low Carbon City (ILCC) in Shenzhen as the case study area, the simulations are performed for 35 days during the hottest month from July to August in the year 2013. The average values of air temperature, moisture, wind velocity, building anthropogenic heat release and the corresponding thermal comfort evaluation index SET* and the local heat island intensity (LHII) in each block were simulated. Then, using the geographic information system (GIS) technology, the thermal climatic maps of ILCC were obtained to reflect the spatial distributions of different meteorological parameters, thermal comfort index and the LHII. The quantitative relationships between the underlying surface parameters and outdoor thermal climate were finally determined accounting for the underlying surface information. The results show that the main region of ILCC is characterized by the weather conditions of high temperature, high humidity, and low wind velocity. The temperature difference among region blocks in the nighttime is larger than that in the daytime. Through a regression analysis, it is found that all the meteorological parameters are greatly influenced by a variety of underlying surface parameters. Some actions such as improving the floor area ratio, increasing the proportion of the public buildings and decreasing the proportion of impervious underlying surface coverage could relieve the LHII and improve the outdoor thermal comfort. In summary, the new method integrated the urban canopy model and GIS technique was proposed to implement the evaluation of outdoor thermal environment and thermal comfort, especially for the complex urban construction area. This plays an important role in accurately and efficiently integrating the layout of different kinds of urban underlying surfaces.
CLIMATE AND ENVIRONMENTAL PLANNING: A CASE STUDY ON INTRA-URBAN AREA OF THE CAMPUS I UFPB
The changes occurred in the urban climate system are processes related to crowding urban and the different forms of use and soil cover. This manner, the understanding of urban climate is essential for the environmental planning of urban areas. It is within this context, that the work is presented, with the aim of analyzing the urban climate system, thermodynamic subsystem of Campus I of the Federal University of Paraíba UFPB, correlating with their various forms of use and soil cover. For the implementation of the data collection (temperature and relative humidity) were used thermohygrometers Hobos®. Measurements of air temperature and relative humidity were carried out during the dry season (January to March 2014) and rainy season (June to August 2014), in nine points with different use and occupation of land. The level of thermal stress was measured by the index of Thom (1959) and classified according Santos (2011), adjusted for tropical regions. The types of soil covering for each point monitored were classified into nine classes in accordance with the percentages of vegetation and permeable and impermeable materials. The analysis of the thermal field of the study area and its relation with the physical description of the use and coverage of the soil showed the presence of sectors with coverage consists of impervious materials, such as asbestos, ceramic, concrete, asphalt, metal cover; and permeable materials with exposed soil, grasses, woody vegetation, shrubs and water body - swimming pool. It was verified that these different coating materials of experimental samples and the geometry of the buildings have an influence on the exchange of energy and heat, directly changing the values of atmospheric variables, which control the level of environmental thermal stress, in which only the vegetation cover, played a leading role in the maintenance of low temperatures and the thermal comfort conditions. The difference in the average temperature of intra-urban space Campus I from UFPB ranged between 0.7°C during the drought period and 1.3°C during the rainy season; already the average variation of relative humidity of the air was 8.7% in the period of drought and of 4.4% in the rainy season. Higher temperatures and lower humidity always occurred between ten o’clock to fourteen o’clock and the minimum in the early hours of the daytime. The level of thermal comfort is influenced by microclimatic conditions that are directly related to the physical characteristics of experimental samples. Air temperatures from the reference point (P1), in general, are relatively smaller than average temperatures of other monitored points for being located in a fragment of Atlantic Forest. Thus, one can infer the formation of urban heat island in the study area. Being observed the formation of this phenomenon, especially in point P3, with an intensity of 3.3ºC during the dry season and 1.6°C in the rainy season. The survey was relevant to allow the identification of microclimates, providing data for the territorial planning and the environmental management from UFPB, thus contributing to raising the ideal conditions of thermal comfort and environmental quality.
Human thermal comfort within an urban district dependent on topography and different planning scenarios - numerical case study for the city of Stuttgart (Southwest Germany) on a heat wave day
Albert-Ludwigs-University of Freiburg, Germany
Facing the combination of regional climate change and demographic change in Central Europe, a task for urban planning with increasing importance is represented by the development and application of methods to maintain human thermal comfort within urban districts during severe summer heat. They should be based on quantitative findings in urban human-biometeorology. The planning methods are related to the current urban land use but also include scenarios for planning projects. If necessary, topographic effects have to be considered.
For that purpose, numerical simulations by use of suitable models have to be performed to obtain the required human-biometeorological information. The spatiotemporal behaviour of meteorological variables should be simulated in a grid width, which provides quantified values for applications in urban districts. As the methods of urban planning aim at the mitigation of local impacts of severe heat on citizens, the models should be able to simulate the human-biometeorological conditions in terms of at least mean radiant temperature MRT and a thermo-physiological assessment index like the physiologically equivalent temperature PET.
As an application example, respective numerical simulations were conducted for an urban district in the city of Stuttgart (Southwest Germany) on a heat wave day. The urban district with an existing planning project is located in a slightly heterogeneous terrain. For the simulations, the ENVI-met model, version 4.0 BETA, including the sub-module BioMet, version 1.0, to calculate PET was applied. Compared to previous versions of ENVI-met, topographic effects on meteorological variables can be now simulated. An implemented forcing function plays a part in contributing to reliable simulations results like for the near-surface air temperature T, MRT and PET.
The simulation domain for the urban district in Stuttgart covers a horizontal area of 450 m • 450 m. The 3-D grid width is 3 m. The numerical simulations were performed for different urban land uses: (i) current situation, (ii) hypothetical use as asphalt area, (iii) hypothetical use as green area consisting of grassland and trees, (iv) current planning project including green areas, and (v) current planning project without any green. With respect to the daytime period 10-16 CET and the nocturnal period 22-5 CET, the results - both grid and areal values for T, MRT and PET - are presented und discussed in a comparative way for the simulated land uses.
The impact of green space distribution on the microclimate of idealized urban grids.
Aristotle University of Thessaloniki, Greece
The study seeks to answer the question of what is the optimal distribution, if such exists, of a given total area of green space within an idealized urban grid in microclimatic terms. The positive cooling effect of green spaces is well documented mostly through in situ measurements or simulations of real world locations. Yet, the diversity of climatic and development conditions of these studies often makes it difficult to produce some general guidelines that can inform the design process for specific locations. This problem is addressed by conducting a parametric analysis using the ENVI-met V3.1 microclimate simulation program for the Mediterranean climate of Thessaloniki and for a typical summer day. The analysis examines a number of different spatial configurations of tree-planted spaces overlaid on a regular idealized urban grid, assuming a fixed green space area. The results are then compared to a reference case of the same urban grid simulated without the green spaces. The resulting differences in air temperature and PET biometeorological index can be used to assess the potential of each configuration in improving thermal comfort inside and outside the green spaces.
An economical method to estimate the air temperature and humidity around buildings on long time scales
1Nanjing Tech University, China; 2South China University of Technology, China
INTRODUCTION: The microclimate around a building, establishing through the interaction with the surroundings, is a significant factor affecting indoor environmental quality and building energy performance. Some simulation tools (such as ANSYS Fluent and ENVI-met) are capable of modeling the microclimate at street scale. However, the computational time for these CFD-based models is rather long since the geometric features of an urban fragment and the complex physical processes are involved. Such CFD-based models are only suitable for microclimate simulations on short time scales (a few hours or days). This study outlines a method to estimate the mean temperature and humidity of the air around a building on long time scales (a few months or a year).
METHODOLOGY: For a certain street context, it can be assumed that similar microclimate patterns will present for the days which are meteorologically homogeneous. So if the microclimates for the representative days of different weather types are obtained, it would be possible to estimate the general features of the microclimate on long time scales. The procedures of the method are as follows: (1) an objective classification methodology, consisting of a principal components analysis followed by a cluster analysis, is applied to the EnergyPlus weather data (EPW) to identify synoptic weather types and the representative day of each weather type; (2) after inputting the district configurations (buildings, pavements, greenery, etc.) into the ENVI-met model, the required sample data set for training neural network predictors is obtained by running the ENVI-met simulations for each of the representative days; and (3) once the optimal neural network ensembles are trained, the air temperature and humidity around the studied building for a long time frame can be predicted by taking the corresponding EPW data as inputs.
RESULTS AND CONCLUSION: A series of comparative simulation cases, including different locations and climate conditions, are conducted to evaluate the accuracy and efficiency of the proposed method. The air temperature and humidity around the studied building estimated by the proposed method are compared with the results obtained by directly running the ENVI-met simulation for the entire studied period. Acceptable agreements are found between the direct ENVI-met simulation and the proposed method, with relative errors of less than 4% for air temperature and less than 6% for air humidity. The comparing results indicate that the proposed method can significantly save computational time with relatively little loss in accuracy. The proposed method can be a workable way for the estimation of the air temperature and humidity around a building on long time scales.
Quantifying the impact of surface heterogeneities on the radiative response of a simplified urban surface
1University of Reading, Department of Meteorology, United Kingdom; 2Tokyo Institute of Technology, Department of International Development Engineering, Japan; 3University of Gothenburg, Department of Earth Sciences, Sweden
Radiation exchanges at the urban surface strongly influence climate conditions within cities. Therefore they directly impact outdoor human thermal comfort, have implications to building energy use and partly determine the energy available to turbulent surface fluxes. The radiative response of the urban surface is a function of both material composition and geometric arrangement of the surface objects. Hence it is crucial to understand how both aspects integrate to the bulk surface characteristics of albedo and emissivity to successfully interpret observed energy exchanges and provide realistic values for model parameterisations. Radiation fluxes are often observed with radiometers installed above the urban canopy. Given the latter is spatially complex and its interaction with the incoming solar radiation may change over time, dynamic modelling approaches are required to relate the fluxes observed to the surface source area.
In this study the relative importance of material properties and the three-dimensional surface structure on radiation fluxes at different locations above the urban canopy are considered. Both long- and shortwave radiation fluxes were observed atvarious locations above a simplified urban setting, the Comprehensive Outdoor Scale Model experiment for urban climate (COSMO; Tokyo Institute of Technology, Japan) and high-reflectance materials were installed in the source areas of the radiometers for certain periods. Surface temperatures of all facets were measured by thermal imagery to provide further insight into radiative heating and cooling of the various surfaces. The simplified canopy allows for the spatio-temporal variations observed to be directly associated with certain source area characteristics (e.g. fraction of roof surface). Observations are compared to results from the dynamic radiation model SOLWEIG (Lindberg et al. 2008), characterising the spatial variations of radiation fluxes across the whole canopy. Given SOLWEIG can also be applied in complex, real city settings, conclusions drawn help to advance source area calculations of radiometers operated in many urban climate studies.
Lindberg F, Holmer B, and Thorsson S (2008): SOLWEIG 1.0 – Modelling spatial variations of 3D radiant fluxes and mean radiant temperature in complex urban settings. Int J Biomet, 52, 697–713.
Street geometry design and its effect on mean radiant temperature: A parametric study based on numerical modelling
1Department of Earth Sciences, University of Gothenburg, Sweden; 2School of Architecture, The Chinese University of Hong Kong, Hong Kong
The spatial variation of hotspots, in terms of their locations and magnitude, is examined in the present study, using the Solar and LongWave Environmental Irradiance Geometry (SOLWEIG) model. The effect of street geometry design parameters such as H/W ratios and street orientations on the radiant heat load are analyzed for three European cities with different regional climatic conditions. Various physical configurations of street trees are examined for their corresponding potential in mitigating the radiant heat load within urban structures. Findings suggest that a dense urban structure (H/W ratio ≥ 2) is capable of reducing radiant heat load at street level. High H/W ratios do not only reduce the magnitude of hotspots, but also changes their spatial distribution. The N-S canyons are found to be more favourable than the E-W canyons since they limit sun exposure to several hours at noon, despite of the diminishing difference between two orientations when H/W ratio increases. Diagonal streets reduce the magnitude of hotspots but increase the areas affected by moderately high mean radiant temperature (Tmrt). NE-SW orientated streets exhibits higher average hourly Tmrt during daytime since they are largely sun-exposed at the hottest time of the day. The highest mitigating effect of street trees is found when they are located in the sunlit areas. The reduction in average Tmrt decreases with increasing H/W ratios but considerable mitigating effect is still observed in the NE-SW orientations. It is also observed that larger tree crowns, even with higher spacing between individual trees, provide better shading than closely placed trees with smaller tree crowns. The present study provides information about the locations and magnitude of hotspots in different urban settings as well as the design of street trees as a mitigation measure to radiant heat load. It helps urban planners and designers to better design neighbourhoods in order to improve pedestrian thermal comfort within urban areas.
Validation of ENVI-met PMV values with in-situ measurements
1Changwon national university, Korea, Republic of (South Korea); 2National Institute of Ecology, Korea, Republic of (South Korea); 3Kyungpook National University, Korea, Republic of (South Korea)
Recently, as the thermal environment has deteriorated in urban areas because of the heat island phenomenon and increases in the frequency of heat waves, those vulnerable to heat waves, such as elderly people and children, are adversely affected and have to limit various outdoor activities, especially in summer. Because of this issue, many researchers are assessing thermal comfort by using the predicted mean vote (PMV) calculated with the ENVI-met microclimate model. However, in Korea, there is a lack of studies that have validated the modeling results by comparing them with in-situ measurement data.
Therefore, by targeting the plaza and walking spaces inside the Changwon National University campus located in the southern region of South Korea, this study aims to calculate the PMV with ENVI-met 3.5 and conduct a comparative validation with the in-situ measurement data. After considering various spatial characteristics such as land cover, buildings, trees, and shading, 27 in-situ measurement locations were selected for further analyses. The measurements were done from 8:00 to 17:00 on September 20, 2014, and by moving from one measurement location to another, the measurements were taken four times. The air temperature, black bulb temperature, humidity, and wind velocity were measured with a TESTO 480- PMV instrument, and the radiant energy was measured with a CNR4 net-radiometer. The PMV by in-situ measurements was calculated by setting the metabolic rate to 2.0 and the clothing level to 0.7. The PMV using ENVI-met was estimated for the time range of 12:00–15:00, which is when the solar radiation was highest.
The highest PMV values (3.0–4.8) based on the in-situ measurements were found at the locations covered with grass or clay blocks without shade. Conversely, thermal comforts were relatively good (values of less than or equal to 2.5) at locations where shade was present as a result of buildings or trees. During the comparison of PMV values obtained by ENVI-met and in-situ measurements, a R2 value of 0.45 was calculated. At most locations, the in-situ measurement data and the modeling results showed similar patterns, but at locations planted with trees, large differences were shown. Therefore, to improve the accuracy of modeling results in the future, the collection of more accurate input data will be required for the heights of trees and Leaf Area Index (LAI).
Analysis of the Cool Roof Effect through a Building Modeling Experiment
1Changwon National University, Korea, Republic of (South Korea); 2National Institute of Ecology, Korea, Republic of (South Korea); 3Kyungpook National University, Korea, Republic of (South Korea)
The use of cool roofs with high reflectivity and emissivity has been recommended in the USA and Europe to help mitigate the urban heat island phenomenon and reduce the amount of energy needed to keep buildings cool in the summer. Accordingly, this study aims to conduct a building modeling experiment to validate the cool roof effect in the southern region of South Korea, which is located in the temperate climate zone at middle latitudes.
The building models were fabricated as 1,000 mm long cubes with sandwich panels. The thickness of the insulation material was set to 150 mm for the roof and 100 mm for the walls and floor. A total of nine models were constructed with different colors and roofing materials. The cooling effect was analyzed by using the measurement data of surface temperature and radiative energy for the model roofs, and the surface temperature, temperature, and humidity of ceilings inside the model buildings were analyzed from late spring to early fall. For the measurement devices, a contact type thermometer, thermo-hygrometer, CNR4 Net-radiometer, and thermal infrared thermometer were used. The reflectivity and emissivity of the roofs for each model were calculated with the radiative energy measurement data and the Stefan–Boltzmann equation.
The analysis results for roof color showed that compared to the green-colored roof (0.112 reflectivity and 0.807 emissivity), the white-colored roof (0.596 reflectivity and 0.886 emissivity) had a surface temperature that was 23.60°C lower at maximum and 3.31°C lower on average; and the temperature inside the model was 2.80°C lower at maximum and 0.30°C lower on average. The analysis results for roofing material showed that compared to asphalt shingle material with a green color, the roof painted with waterproof paint of the same color on the sandwich panel had a surface temperature that was 17.40°C higher at maximum and 1.05°C higher on average; and the internal temperature was 3.50°C higher at maximum and 0.14°C higher on average. Compared to the white-colored roof, the green roof planted with Mukdenia rossii (Oliv.) Koidz. had a surface temperature that was 9.10°C higher at maximum and 0.05°C higher on average; and the internal temperature was 2.80°C lower at maximum and 0.11°C lower on average. Through the building model experiment, it was confirmed that white-colored roofs with high reflectivity will have a higher cool roof effect than green roofs, which are similar to the green-colored roofs that are most abundant in South Korea.
Since South Korea is in the temperate climate zone where four seasons are distinct, a follow-up long-term monitoring study is necessary to analyze the potential for the occurrence of adverse effects such as heating cost increases in winter.
Study of human thermal comfort for architecture in China – The Example of Shanghai
Architecture focuses mainly on producing and performing a design proposal for an area, thereby forming a new urban structure. However, until now, it rarely utilises the knowledge on human thermal comfort to modify the outdoor recreational space. In order to provide a comfortable outdoor space, thermal comfort should be taken into account in the design phase of urban architecture. The Physiologically Equivalent Temperature (PET), one of the thermal indices, could indicate how human beings sense the actual thermal environment by values with Celsius degree. The objects of this study are to analyse and evaluate the thermal conditions for urban architectural design in a residential district in Shanghai, China. Basic meteorological data (3-hour resolution) have been used. RayMan model has been used to calculate PET in order to analyse the long-term thermal conditions in Shanghai. ENVI-met model has been used to simulate the micro-atmosphere conditions of this residential district in order to gain the short-term specific thermal conditions. The results show that the hottest month during 2000-2012 was July. Based on the thermal conditions in July, the simulations show that the hottest area in one day at LST 1400 was the southwest side of buildings with PET higher than 54 °C. Evaluation and visualisation of the thermal comfort would help landscape and urban architects identify the particular area before designing, thereby modify the thermal condition specifically.
Mean Radiant Temperature in urban spaces from solar calculations, climate and surface properties – theory and 'Mr.T' software
1Institute of Soil, Water and Environmental Sciences, ARO Volcani Center, Israel; 2Department of Geography, Tel Aviv University; 3Department of Electrical and Electronics Engineering, Tel Aviv University
Mean radiant temperature (TMRT) is an important component of human thermal comfort indexes, but is difficult to measure and model. A method was developed to calculate instantaneous values of TMRT based on the geometry and dimensions of the urban canyon, vegetation leaf area index, meteorological data (temperature, relative humidity and solar radiation), surface emissivity and reflectivity, and surface temperatures in the urban canyon. The advantage of this method is that it can be used for experimental work in the urban canyon without the need for deploying several expensive radiometers, eg. four-flux net radiometers. The calculation procedure involves calculation of extraterrestrial, direct and diffuse solar radiation, sky long wave radiation, and reflections and emission of radiation from the various surfaces. A software package, named Mr. T, was developed as a final project of two engineering students, to include the various calculations and allow determining TMRT from the appropriate input data. The package has a friendly user interface and can accept data input manually or from EXCEL type spreadsheets. The calculation procedure and software were tested in two urban settings at and near Tel Aviv University and results were not significantly different from those obtained with four-flux net radiometers. The software package will be supplied freely to the research community. The calculation procedure and software should be important for use in determining thermal comfort in the appropriate models.
ARIStree – A L-System-Based Plant Modeling Tool for ENVI-met
Johannes Gutenberg-University Mainz, Germany
Plants have a significant impact on the microclimate. Therefore the modeling of plants is an important part when simulating complex microclimate systems. Our new tool is based on Lindenmayer-Systems (L-Systems), in order to build a most realistic image of the geometry of plants.
L-Systems were introduced by Aristid Lindenmayer and are parallel rewriting systems having a formal grammar consisting of an alphabet of possible symbols. Starting with an initial axiom, this method generates geometric structures by following production rules and a translating mechanism that expands each symbol into a larger string of symbols. This string needs to be interpreted for getting the plant structure.
The new tool ARIStree is an adaption and enhancement of this method for the microclimate model ENVI-met. It allows reproducing the geometry of plants which has to be modeled for the simulation. Having a geometry which represents the original plant as exact as possible allows e.g. derivating the correct leaf area density for every grid cell of the plant in the model.
Besides finding the best fitting axioms and production rules as well as the parameters (e.g. angle or size of branches) for the corresponding plants in the model, the implementation and enhancement of powerful and efficient algorithms for the translating mechanism is very important, because the user should be able to control the whole construction process by checking instantly the results of his changes.
Therefore this new tool provides the possibility to control the whole modeling process stepwise. For that purpose ARIStree provides a graphical user interface.
The user can manipulate an existing plant from the database or construct a totally new plant by editing the set of input parameters (e.g. axiom, production rules, plant parameter). Furthermore he can choose a generic plant from the database by selecting the L-System such that the tree has a specified branching property (monopodial or sympodial branching tree). Additionally, the user can control various leaf formations (distichy, dispersion and decussation) as well as the kind and intensity of tropism.
This work presents an adaptation and enhancement of the well known Lindenmayer-Systems for plant-modeling in complex environments. The here presented tool is called ARIStree – in appreciation of Aristid Lindenmayer, and allows the user to create L-System based modeled plants for the ENVI-met database. The resulting plants can be used in ENVI-met simulations by the same way as the existing plants but they offer a more detailed representation of the geometry of the modeled plant. Last but not least, the way of modeling plants in ARIStree is more comfortable.
Optimizing Outdoor comfort of pedestrian and open space in cities base on climatic conditions ,Case study the KASHAN city.
rajaee, university, Iran, Islamic Republic of
The outdoor comfort of pedestrians and sidewalks has been neglected by architects and planners because of difficulties in determining comfortable and uncomfortable climatic conditions and predicting the climatic characteristics of a planned urban site.. The mechanical effects of wind on comfort are better understood than the thermal effects of climate and have proved to be practical criteria for assessing pedestrian comfort in designs .Climatic-prediction techniques and a procedure for determining the probability of discomfort on a proposed site are described. in this study ,we use models (Penwarden,ET,…) for determining of comfort climate in outdoor space such as sidewalks and pedestrian in city of KASHAN .
Outdoor comfort, comfort zone, pen warden, KASHAN city
Temporal differences of urban-rural biometeorological factors for planning and tourism in Szeged, Hungary
1Albert-Ludwigs-University Freiburg, Germany; 2Department of Climatology and Landscape Ecology, University of Szeged
Tourism is an important economic sector in Hungary. Beneath other parameters, weather and climate are not only advantageous factors but also limiting factors for tourism. Heat load and cold stress can provoke annoyance and even health issues. These climatic situations should be avoided by tourists and locals to prevent negative experiences. A better knowledge and information flow about the climatic conditions in Hungary and its regions are needed. Usually, weather information services provide single meteorological parameters like air temperature, sunshine duration, precipitation or wind speed, but this is unsatisfactory to describe the impact on and the sensation for humans. Thermal comfort indices are required, as they combine meteorological and personal parameters. In this study the thermal index Physiologically Equivalent Temperature (PET) is used. PET is easy to understand, interpret and to apply also for non-experts like tourists or decision makers. The Climate-Tourism-Information-Scheme gives a well-arranged overview of all climatic and bioclimatic relevant parameters for tourism. It presents the possibility of thermal acceptance, heat stress, cold stress, cloudiness, fog, sultriness, wind velocity, dry and wet days per ten day decade. The Hungarian Meteorological Service and the University of Szeged provide an urban and a rural weather station near Szeged, which build the basis for the biometeorological analysis for a twelve year period between 2000 and 2011. The maximum, mean and minimum air temperatures of both stations were compared to detect the differences of climatic dynamics. Heat and cold stress are quantified by analyzing the PET frequencies at 14 CET. The air temperature of urban areas is averaged 1.0 °C warmer than rural areas (11.4 °C). Heat stress is more frequent in urbanized areas (6.3 %) during summer months at 14 CET, while thermal acceptance is more frequent for surrounding rural areas (5.9 %) in the same period. The warmer season starts earlier in urban areas and ends later in the year than in outer conurbation areas. Cold stress dominates at both stations during the winter, with a probability of about 90 %. Szeged has a mean annual amount of precipitation of 520mm with big annual fluctuations. Most of its precipitation falls during summer, as it is typical for continental climate. The mean total cloud cover is averaged 2 octas higher during winter than during summer. With about 2,100 hours of sunshine per year, Szeged is known as the "City of Sunshine" in Hungary. The Climate-Tourism-Information-Scheme is a feature to present the meteorological and biometeorological data which is interesting for decision making and tourism in a well-arranged way.
Key-words: Thermal Index, Physiologically Equivalent Temperature, Heat Stress, Cold Stress, Tourism, Szeged, Hungary
Analysis of 3D radiant fluxes using SOLWEIG in complex urban area
Weather Information Service Engine Project, KMA, Republic of South Korea
The increasing number of people living in urban areas accentuates the need for an improved understanding of how the environment within cities affects people’s lives. The variation in urban micro-climates produce a wide range of conditions which can impact people’s health (human thermal comfort). Urban thermal environment is very important factor because directly related to the health of citizens. The energy budget is necessary which has been happening in city, which is analysis of heat flux to consider mutual relations among heat, environment and other factors which have influenced to sense and behavior of people. The mean radiant temperature, Tmrt, which sums up all shortwave and longwave radiation fluxes (both direct and reflected) to which the human body is exposed is one of the key meteorological parameters governing human energy balance and the thermal comfort of man. The SOlar and LongWave Environmental Irradiance Geometry(SOLWEIG) model simulates spatial variations of 3-D radiation fluxes and Tmrt as well as shadow patterns in complex urban settings. There are several different methods of measuring and modelling Tmrt. The most accurate of these includes all shortwave and longwave radiation fluxes(upward, downward and from the four cardinal points), angular factors, human shape, etc..
This study includes not only establishing of high resolution (2m)-building and input data of vegetation distribution about Jungnang (residential area) district in Seoul, but also comparing and analysis of 3-D radiation fluxes through net radiometer data and the results of SOLWIEG(ver.2013a).
Analysis and modelling of meso- and microscale urban climate in Bucharest, Romania
MCR University Basel, Switzerland
Urban climate has been investigated and monitored over years and gains more importance due to the increasing number of people living in an urban environment worldwide. In the context of global climate change and the increasing number of extreme events (such as deadly heat waves) expected for the future, the understanding of dynamics and processes of urban climate is a crucial topic in climate sciences. In this study, the urban climate of Bucharest was analysed and modelled in different scales using different approaches. The mesoscale urban climate was investigated using data from the recently launched Landsat 8 satellite. Thereby, a land surface analysis map was created with a multi-temporal approach using regions of interests and a maximum likelihood classifier. To evaluate connections between the vegetation cover, the surface albedo and the land surface temperature with the land surface cover, the produced map was segmented and the classes were treated separately. In a second step, the 3D micro climate model ENVI-met was used to model the influences of urban development in downtown Bucharest on the local urban climate. Thereby, the constructional changes occurred in the city centre after an earthquake in 1977, were modelled using Corona images and recent city plans. As a third scenario, a possible future state with lower vegetation cover was developed. To quantify the significance of the urban development and the modification of the urban climate to human health, the predicted mean vote, a measure for thermal comfort, was calculated during the model runs and displayed using ENVI-met Leonardo. The mesoscale analysis showed the appearance of a primary surface urban heat island and connections between the land cover and the land surface temperature, as well as between the vegetation cover and the land surface temperature. The microclimate modelling showed differences in the vertical temperature distribution and the wind field during the different scenarios. Thereby, the nocturnal cooling in the canopy layer was most apparent in the former state scenario. Comparison of the thermal comfort within the city between the former state, the current state and the future state revealed an increasing thermal stress in most parts of the investigation area, due to the constructional changes and especially in case of the cleared vegetation cover. Due to the high number of data produced during this work, future studies are inevitable.
Raytracing of solar radiation for urban microclimate study
National University of Singapore, Singapore
As cities get larger and denser, the Urban Heat Island (UHI) effect occurs, which is the temperature difference between the urban and rural surroundings. One of the biggest contributors is the heat source coming from the climate of sun and sky radiation. To design our cities better, one of the best interventions that can be made is to have forms that respond well to minimize the heat gain. Therefore, more simulation studies are done today to compare various forms and how they impact the solar radiation received, which has a big implication in energy consumption. For the tropics like Singapore, it will mean more energy required for the cooling load to overcome the heat gain indoors.
RADIANCE has been the industry standard software used for the analysis and visualization of lighting studies (Ward Larsen and Shakespeare,1997). It is a highly accurate ray-tracing software so much so that it is considered a truth model for comparisons (Robinson and Stone, 2004). It has been widely used for outdoor urban environment solar radiation studies (Hii et al., 2011) and daylight studies (Zhang et al, 2012) too. However, it does not do heat transfer calculations and hence, will not be able to report the temperature increase caused by the climate.
In the CFD (Computational Fluid Dynamics) realm, the use of solar radiation using raytracing method as well in the urban environment studies has been quite recent (Bottillo et al., 2014; Nazarian and Kleissl, 2014; Toparlar et al., 2014; Taleb and Musleh, 2015) with more focus done on the surface convective heat transfer aspects (Lei et al., 2012; Magnusson et al., 2014; Saneinejad et al., 2011; Xie et al., 2005, Xie et al., 2007, Kim and Baik, 1999). The CFD has the energy equation that helps translate the energy received via heat transfer from solar radiation to the urban surface and air temperature rise.
However, thus far, there has been no comparison studies done to compare the results of the raytracing methods used in both the RADIANCE and the CFD software for high density urban environments, which is classified as Local Climate Zone 1 which is compact high rise (Stewart and Oke, 2012). The height-to-width (H/W) ratio of 2 and above is defined for such a dense urban environment. In the urban environment, CFD validation has only been done for urban ventilation studies with best practices done by various parties like COST (European Cooperation in Science and Technology) (Franke et al., 2004) and AIJ (Architectural Institute of Japan) (Tominaga et al., 2008) as well as (Blocken and Gualtieri, 2012).
The motivation of the study is to compare the solar radiation results by RADIANCE and the CFD software for the high density environments in the tropics comparing various urban forms. Since it is about radiation, the influence caused by the same material in both software can be compared too. The results will therefore inform the user whether they can run the solar radiation simulation directly in the CFD environment together with other heat transfer aspects of convective and conduction in addition with fluid flows for ventilation studies. This is crucial since the transient process of the solar radiation contribution will help in the full understanding of the urban microclimate as it impacts the urban energy balance.
Evaluation of mitigation strategies to improve pedestrian comfort in a typical Mediterranean city
1University of Salento - DISTEBA - Lecce (Italy); 2ALMA MATER STUDIORUM - University of Bologna - DIFA - Bologna (Italy); 3RESEAUX S.r.l. - Lecce (Italy)
The increasing urbanization has posed great attention to enhanced temperatures in the cities. This thermal trend is exacerbated by the reduction of green coverage (parks and trees) which is considered an important feature to improve pedestrian comfort through shading and increased evapo-transpiration. Compared to other mitigation strategies, the increase of vegetation areas induces a significant reduction of the sensible heat flux which mostly affects the surface energy balance. Nevertheless, the capability of vegetation such as trees in mitigating high temperatures must be set off against the trapping effect at street level reducing the cooling during the night. Modelling techniques are a powerful tool to investigate such issues and to establish mitigation strategies tailored to improve pedestrian comfort.
In this perspective, we make use of the Computational Fluid Dynamics (CFD) technique to identify key processes and factors that mostly influence temperature and humidity and to quantify thermal effects of several mitigation measures and varying meteorological parameters in several sites of Lecce (south Italy). The performance of both the current release of the CFD-based ENVI-met (v3.1) and of the new version ENVI-met v4 (currently released as a technical preview) is evaluated against field measurements held during summer 2012.
Specifically, we simulate three different case-studies of a Mediterranean climate, namely a typical summer day, a summer hot and dry day and a high humidity condition for which thermal comfort indices are evaluated. Mitigation strategies of thermal stress are then assessed through the implementation of green infrastructures (urban forestry and green roofs). The intent is (i) first to show which atmospheric condition enhances the effectiveness of vegetation in mitigating potential temperatures, mean radiant temperatures and PMV (Predicted Mean Vote); (ii) then to select the most favorable mitigation strategy for the different case-studies.
Each chosen mitigation strategy is further analyzed by employing the CFD code Fluent to assess other effects of urban trees in street canyons, such as the obstruction effects to the wind and the trapping of traffic-related pollutants. Trees themselves represent in fact obstacles to air flow which can reduce ventilation compared with tree-less areas and increase pollutant concentration. These effects are evaluated through the estimation of building ventilation concepts, such as the mean flow rate and the mean age of air, and detailed investigation of turbulent momentum and heat exchanges between the street and the atmosphere above.
The heat stress assessment of two contrasted outdoor urban environments: the examples of Lisbon (Portugal) and Bucharest (Romania).
1CEG/IGOT University of Lisboa, Portugal; 2Administratia Nationala de Meteorologie
The bioclimatic and public health impacts due to thermal stress (associated with the spatial patterns of the Urban Heat Island – UHI) will be a major issue for future urban planning authorities. Accordingly to the latest Working Group II Summary for Policy Maker of AR5 of IPCC (2014) heat waves are one of the key risks for Europe, and particularly to the European urban areas. To design better cities and improve the quality of living in urban areas, more quantitative information about outdoor thermal comfort is needed, on various temporal and spatial scales. Recent studies emphasize the importance to clarify “how future urban expansion and global warming will act together and to ascertain their combined effect on the local climate”. In this topic the microclimate modeling could be an important tool to evaluate changes in atmospheric parameters that affects thermal comfort (e.g. air and surface temperatures; Mean Radiant Temperature, wind speed, humidity, etc) in the urban canopy layer (UCL) and to validate adaptation and mitigation strategies in urban areas.
The overall objective of this study is to evaluate outdoor human thermal comfort under heat stress conditions in two European cities (Lisbon/Portugal and Bucharest/Romania) within two different geographical settings. The modeling analysis is focused on air and mean radiant temperature, and ventilation, and it will be achieved using several micrometeorological models (e.g. ENVI-met, Solweig, Rayman).
The specific goals of this research are: i) to compare urban climate of two different cities and thermal physiological response to heat stress; ii) to quantify the effect of urban green spaces in the city centers of Lisbon and Bucharest; iii) to calculate and compare the results of the Physiological Equivalent Temperature (PET) and Universal Temperature Climate Index (UTCI) in the two cities; and v) to propose and validate specific measures of adaptation in these areas.
Keywords: Bioclimatology; Urban climate change; Human Thermal comfort; Heat Stress; Micrometeorological modeling.
Analysis of 3 Dimensional Sunshine Duration Environment in an Urban Area
PUKYONG, Korea, Republic of (South Korea)
In this study, sunshine duration environment in an urban area is analyzed using a numerical model which considers sunshine‒duration blocking by topography and buildings. The numerical model used in this study has an improvement in the algorithm detecting sunshine duration at any place in the model domain. The main improvement in the algorithm is to detect sunshine duration using all the surfaces of any grid cell (the previous model uses the center of any grid cell). The improvement in the algorithm gives more accurate evaluation of sunshine duration at corner surfaces of buildings. Using the improvement model and geographic information system (GIS) data, sunshine duration environment is analyzed at a building congested area in Busan for a week in each season. The results show that sunshine duration can be much changed by apartment complexes, high‒rise buildings, and topography in the model domain. Also, the effects of a recently constructed high‒rise building on sunshine duration environment for a neighboring area are analyzed.
The variation of sky view factor from urban geometry
1Ulsan college, Korea, Republic of (South Korea); 2The University of Manchester, School of Mechanical, Aerospace and Civil Engeineering,United Kingdom
The sky view factor (SVF) contributes the urban heat island (UHI) effect for shielding from the sky. It is possible to generate sky view factor values for calculating SVF from the hemispherical image and simple model. This paper estimate various forms of urban geometry and sky view factor using simple hemispherical image. This can be used to represent the ratio of long wave loss from surfaces.
PLANNING OF GREENING BASED ON INTEGRATED EVALUATION OF THERMAL ENVIRONMENTS AND ECOSYSTEM
Shimizu Corporation, Japan
In recent years, planning of preservation and creation of greening in urban space are advanced. There are several purposes to create the green space in Japan. For example, trees have been planted around the high-rise building for the purpose of wind speed reduction. Of course, green spaces have been created to mitigate the urban warming by the reduction of air temperature. Furthermore, the importance of ecological network has been pointed out from the viewpoint of urban biodiversity in recent years. Compatibility of the urban climate regulation and the habitat creation is expected as ecosystem services by urban greening.
In order to create the good environments for many organisms and human, it is important to understand and use the various effects of greening. The purpose of this study is to comprehensively evaluate the effect of green space. In this paper, not only the thermal environments in the outdoor space as the impact on the human thermal sensation, but the ecological network as the effects on the habitat of organism in the surroundings were evaluated for several greening plans near the central part of Tokyo.
In terms of the thermal environment, coupled simulation of radiation, conduction and convection were conducted. Finally, human thermal sensation was evaluated by SET* using the results of simulation data. For ecological network, using the satellite images and the habitat suitability model, the ripple effects on the potential habitat of Japanese Tit (Parus minor) by greening plans were quantitatively evaluated.
As a result, increasing of green spaces was shown the positive effects for ecological network, but too much tree plant show the negative effect for human thermal sensation because of the wind velocity reduction in the hot and humid summer. Trade-offs between the climate effect and the ecological effect could be evaluated quantitatively and comparably in the environmental considerations of urban greening.
Effects of changing surface characteristics and design on the microclimate of a tropical urban area using the model Solene
Federal University of Minas Gerais, Brazil
Natália Carolina Sousa Nascentes Marra, Eleonora Sad de Assis
The aim of this study is to analyze how the changes in the facade materials of buildings, in the urban design and substitution of concrete pavement for vegetation can influence the indoor air temperature and the outside temperature of the surfaces. The case study is a housing complex that is being constructed in several areas of the city of Belo Horizonte, Brazil, for the population removed from slums and geological risk areas. The methodology used was the computer simulation of the complex by means of the microclimatic model Solene developed by CERMA Laboratory. It was considered three summer days as the climatic conditions. The following situations were simulated: (a) the actual situation of buildings, dark colors on the facades and little clearance between the blocks, (b) light colors on the facades and little clearance, (c) dark colors and vegetated soil and (d) greater spacing between the buildings. The results showed that changing albedo of the facades, as well as the concrete pavement by vegetation covering, provided a decrease both in the indoor air temperatures and in the external surface temperatures. The spacing between the blocks reduced the shadows which was not found satisfactory in some areas since there was an increase of the temperature due to a greater exposure to direct sunlight. The study showed the importance of a global study in the implementation of residential buildings in order to reduce the temperature in the summer in warm and humid climates such as in Brazil thus providing greater thermal comfort to users.
Using lichen diversity to evaluate the impact of Urban Heat Island Effect
Faculdade de Ciências, Universidade de Lisboa, Portugal
Urban areas are associated with higher temperatures than their surroundings, which is known as Urban Heat Island (UHI) effect. The great increase in buildings, streets and other structures, as well as the heat and atmospheric pollution released by human activities and poor ventilation, leads to this change on local climate in urban areas, whereas urban green spaces alleviate this effect. Urban geometry modifies the principal radiative and energy balance, being those modifications some of the principal causes of UHI. Therefore the arrangement of buildings, their height and spacing influence local climate and are extremely important factors. The UHI effect enhances the impacts of heat waves, which is particularly relevant considering that most of world population lives in urban areas. Using ecological indicators that evaluate the impact of microclimate changes is a way of unavailing the real importance of urban geometry to microclimate changes in urban areas. Lichens communities are the most sensitive groups to environmental changes that occur in the ecosystems since they are poikilohydric. In particular lichen response functional groups, i.e. groups of species with a common response to an environmental factor, have been shown to give an integrated response to the microclimatic variations occurring in urban areas. Our aim was to use epiphytic lichens diversity to understand the effect that different types of land use (buildings and green spaces) have on UHI effect. It is also our aim to understand how urban geometry, e.g. different highs of buildings, change the UHI effect. Total species richness, lichen diversity value (LDV) and lichen functional groups regarding humidity requirements and eutrophication tolerance were calculated for different green areas of Lisbon. We expect that green spaces surrounded by tall buildings and narrow streets have more xerophytic and nitrophytic lichen functional groups than green spaces surrounded by small buildings and large streets. These results will help the decision makers of Lisbon urban area about what type of urban geometry is better to alleviate the UHI effect, thus optimizing the urban green infrastructure.