BPH1: Modeling of outdoor microclimate & comfort
The role of trees in urban thermal comfort and SkyView Factor
1Ataturk University, Turkey; 2Ataturk University, Turkey; 3Ataturk University, Turkey; 4Albert-Ludwigs-University of Freiburg
Determination of comfortable places in urban areas is one key issue for urban planning or design processes. In order to determine comfortable places of Erzurum in this study, measurements are made for six different types of tree in the city. These measurements are compared with the data obtained from meteorological station located in urban and rural areas. Additionally, fish-eye photographs at 1.5 m above ground are taken in this study for the calculation of Sky View Factor (SVF). In the context of this study, relationships between air temperature, human thermal comfort and different types of trees have been determined for the city of Erzurum. Meteorological measurements were made three times in one day for summer months and RayMan model was used for the analysis of these measurements. Trees used in this study were Fraxinus americana L (1), Pinus sylvestris L. (2), Salix babylonica L. (3), Ulmus glabra Huds. (4), Betula pendula Roth. (5), Malus hybrida (6). This study was made for defining that trees produce more comfortable conditions during summer months. The relationship between the air temperature under trees and SVF was in addition investigated. The effects of different types of trees on thermal comfort in urban areas for especially summer months were also determined.
It was stated from the ordination analysis that values of Sky view factor (SVF) are independent from azimuth and PET, which must strongly be related to Tmrt and SVF values are proportional to width of corolla and height of plant.
Keywords: Skyview factor, Trees, urban area
Developments and applications of thermal indices in urban structures by RayMan and SkyHelios model
Albert-Ludwigs-University Freiburg, Germany
In order to analyze urban bioclimate and climate several input and output parameters are re-quired. For the quantification of thermal bioclimate assessment methods based on the human energy balance builds the basis of all the known thermal indices.
RayMan model can calculate mean radiant temperature and thermal indices (PMV, PET, SET*, UTCI and PT). For the calculation of mean radiant temperature, which in one of the most influencing parameters of thermal comfort on human, especially during summer conditions, many information about the radiation fluxes (short and long wave), wind speed and modifying factors (Sky View Factor, surface temperature, …) are required.
Some data and information can be obtained from measurement or simulated by micro scale models. This information in combination with shade, sunshine duration, wind speed and direction in simple and complex environments can be derived by RayMan and SkyHelios model. The models are able not only to calculate but also visualize climate and urban climate information based on grid data and vector data. The information can be derived for different spatial and temporal scales depending on the aim and the demands. In addition the Climate Mapping Tool can visualize most of the demanded urban climate data and data formats in combination with SkyHelios. In addition all three models are linked together and can exchange relevant inputs and information.
The application possibilities of the models cover several fields of human-biometeorology including urban climate issues for micro scale. Several possible applications for sky view factors, sunshine duration and thermal indices in complex urban environment will be shown.
Towards a city-wide analysis of mean radiant temperature at high spatial resolution – An example from Berlin, Germany
1Technische Universität Berlin, Department of Ecology, Institute of Climatology, Germany; 2University of Gothenburg, Department of Earth Science, Urban Climate Group, Sweden
Heat stress is expected to increase in the future due to global climate change. Many epidemiological studies show the close link between elevated air temperature and increased morbidity and mortality, which are not restricted to subtropical and tropical regions but also common in cities at higher latitudes like Berlin (52.5° N). Heat-stress risks are particularly high in urban regions, since urban climate modifications of regional weather conditions tend to increase heat-stress hazards.
In order to analyse heat-stress risks and hazards within a city, the mean radiant temperature is an important variable as it sums up long- and short-wave radiation that reaches the human body. Thus, the mean radiant temperature along with air temperature, atmospheric humidity and wind speed is used for the calculation of many biometeorological indices. In urban environments mean radiant temperature is highly variable due to the shadow patterns of objects. To calculate the mean radiant temperature, urban structures such as trees, bushes, courtyards, street canyons and buildings need to be parameterized or explicitly included. The former reduces the computation demand, but limits the possibility to derive planning measures to reduce heat stress. In addition, weather and climate influence the variability of the mean radiant temperature, because the atmospheric conditions are heterogeneous in large urban areas.
Therefore, the aim of this study is to calculate the mean radiant temperature for the case of Berlin while considering both micro-scale urban structures and meso-scale atmospheric conditions. For the computation of the mean radiant temperature we apply a version of the SOLWEIG model (Lindberg et al. 2011) that is able to use gridded meteorological input data. Digital surface models of buildings and vegetation with a spatial resolution of 1m provide the height of the micro-scale urban structures. The Central Europe Refined analysis (CER) serves as input for meso-scale atmospheric conditions.
We will discuss the resulting spatio-temporal pattern of the mean radiant temperature in view of the applied methodology as well as regarding actions to reduce heat stress.
Lindberg, F., C.S.B. Grimmond, 2011: The influence of vegetation and building morphology on shadow patterns and mean radiant temperatures in urban areas: model development and evaluation. Theor. Appl. Climatol., 105, 311-323.
Heat-related health impacts associated with the urban heat island and climate change in the West Midlands, UK.
1University of Birmingham; 2Public Health England; 3University College London
Heatwaves are associated with a range of adverse health effects, which can lead to emergency hospitalisations and mortality. In towns and cities, the Urban Heat Island (UHI) effect i.e. higher ambient temperatures in the city centre compared with surrounding suburban and rural areas, particularly at night, can exacerbate these health effects. The effects of UHIs are often amplified during anticyclonic summer weather conditions, which can cause or exacerbate heatwaves. Climate change projections often do not include the effects of the UHI, due to difficulties in resolving urban scale features. This means that assessments of health effects using these projections may underestimate the actual magnitude of future heat-related health impacts.
Birmingham is the second most populous city in the United Kingdom, and observations indicate that it has a pronounced UHI. Recent modelling showed that replacing urban land categories in the West Midlands with rural ones led to a reduction in 2 metre temperature of around 3 degrees Celsius on average and up to 7 degrees Celsius during the heatwave of August 2003, compared with the baseline urban simulation. In addition, examination of the extent of horizontal advection of warm air away from the city centre indicated that temperatures downwind of Birmingham centre were up to 2.5 degrees Celsius warmer than those upwind.
We present results of a health impact assessment during heatwave periods, based on numerical simulations of the UHI in Birmingham and the West Midlands Metropolitan region using the regional meteorological Weather Research and Forecasting (WRF) model, with an urban canopy scheme. We find that heat-related health impacts associated with the UHI effect are significant and that the heat-health burden will increase in future, based on published temperature projections for the UK. These findings can be used to better quantify the current heat related health impacts relating to the UHI as well as future impacts under climate change scenarios. It may also be used to inform future adaptation measures to protect populations from heat in urban environments.
A contribution to the summertime heat improvement in a marathon course by application of radiate and airflow simulation
National Institute for Land and Infrastructure Management, Japan
Tokyo Olympic Games will be carried out at midsummer of 2020. Therefore a risk of heat exhaustion has been overstated when decision making of outdoor play is revealed. Summertime heat environment focused for the Olympic course in the heart of Tokyo has been discussed in this research. A comprehensive tool considering radiate and wind flows was developed to simulate the thermal impacts to athletes and audiences by taking the measures such as radiation shelter, planting trees and evaporative cool mist.
A Multiscaler Thermal Analysis of Urban Playgrounds
1Texas Tech University, United States of America; 2Arizona State University, United States of America
The ways in which many playgrounds and parks are designed are not conducive for thermally safe and active play by children. Children are more sensitive and vulnerable to heat-related illnesses than the average adult, mainly due to their small body mass-to-surface-area ratio. This results in thermoregulatory difficulties during physical activity in the warm-hot ambient temperatures. Notably, the mean radiant temperature influences surface temperatures of playground equipment, and hence the dangers of burns and heat stress are present, particularly in predominantly sunny climates. Impacts are important to understand due to current and future urban heating and climate effects, urban land use change, growth of urban areas, and a lack of bioclimatic design in warming cities. Urban climate models cannot resolve human-scale or playground-scale effects, and remote sensing (RS) data, although better, also misses subgrid variability that occurs on the scale of centimeters within a playground.
The objective of this study is to address ‘touch-scale’ (hand based) surface temperatures on the order of centimeters, assessing the variability within the various subgrids in order to develop a framework linking the three scales of data. We utilize two sets of surface temperature data collected mid-day in Phoenix Arizona: 1) MASTER (MODIS/ASTER) overflight RS data at a 7m resolution, and 2) in-situ touch-scale data at < 1cm resolution using infrared thermometry. Within Phoenix – the U.S. metropolitan area with the highest summer temperatures – select neighborhood data is focused on two playgrounds within one neighborhood from July 2011 and Sept 2014 (air temperatures of 38^oC). Within-grid variability is assessed to determine the distribution of surface temperatures above or below the mean of remotely sensed data.
Results demonstrate the RS MASTER data for the neighborhood and two parks generally fitting a normal distribution curve, while the touch-scale data has a positive, or right, skew to the higher temperatures due to the presence of materials with high thermal conductivity (metal and plastic slides, metal bars, plastic seats, rubber or artificial turf). These touch-scale values were 20–40^oC greater than the 7m grid mean from the RS data within the playgrounds, reaching maximum magnitudes of 72–87^oC (dark slides, rubber surfaces); under shade however, these surfaces were 23–38^oC cooler.
This study demonstrates that for select surfaces, RS data is sufficient (e.g., roads, roofs, parking lots); however, in playgrounds and other neighborhood locations, this resolution is not accurate enough to quantify extreme and dangerous temperatures. Touch-scale measurements were largely different than remotely sensed temperatures in the playgrounds, yet nearly identical for sand and concrete surfaces. This information provides a paradigm for linking point measurements with RS grid measurements, and a quantitative framework addressed various scales in urban climate research. Applying information to public safety and children’s health, illness and injury due to extreme heat can be avoided, and playgrounds can be designed for thermally safe and active play.