Thermal Bioclimate Research Articles

Evaluation of thermal bioclimate based on observational data and numerical simulations: an application to Greece.

The evaluation of thermal bioclimate can be conducted employing either observational or modeling techniques. The advantage of the numerical modeling approach lies in that it can be applied in areas where there is lack of observational data, providing a detailed insight on the prevailing thermal bioclimatic conditions. However, this approach should be exploited carefully since model simulations can be frequently biased. The aim of this paper is to examine the suitability of a mesoscale atmospheric model in terms of evaluating thermal bioclimate. For this, the numerical weather prediction Weather Research and Forecasting (WRF) model and the radiation RayMan model are employed for simulating thermal bioclimatic conditions in Greece during a 1-year time period. The physiologically equivalent temperature (PET) is selected as an index for evaluating thermal bioclimate, while synoptic weather station data are exploited for verifying model performance. The results of the present study shed light on the strengths and weaknesses of the numerical modeling approach. Overall, it is shown that model simulations can provide a useful alternative tool for studying thermal bioclimate. Specifically for Greece, the WRF/RayMan modeling system was found to perform adequately well in reproducing the spatial and temporal variations of PET.

Thermal bioclimate as a factor in urban and architectural planning in tropical climates—The case of Campinas, Brazil

Urban climate studies can provide information necessary for the improvement of conditions of thermal comfort for people in cities in the Tropics. This paper presents thermal bioclimate analysis of a case study in Campinas, Brazil, using air temperature (Ta), mean radiant temperature (Tmrt), and Physiologically Equivalent Temperature (PET), which can be used as assessment factors for urban and architectural planning in tropical climate. The meteorological data air temperature, relative humidity, wind speed, and solar radiation for the period 2003 to 2010 were used to calculate Tmrt and PET using the RayMan Pro model. Simulations of shade and wind speed variations were performed to quantify changes in thermal bioclimate due to modifications in urban morphology. The results show that solar radiation and wind speed not only influence air temperature, but also more extensive thermal comfort and heat stress as well. Furthermore, the simulations of the variation of wind speed and shade conditions demonstrate that shade can improve thermal comfort situations in terms of PET above 35 °C. The improvement of outdoor thermal comfort is an important step in achieving sustainability of urban spaces and configurations. These results are valuable for architects, planners, and urban designers for the description of conditions and the development of possibilities for improving microclimatic conditions based on urban design and configurations.

Thermal bioclimate in idealized urban street canyons in Campinas, Brazil

Among several urban design parameters, the height-to-width ratio (H/W) and orientation are important parameters strongly affecting thermal conditions in cities. This paper quantifies changes in thermal comfort due to typical urban canyon configurations in Campinas, Brazil, and presents urban guidelines concerning H/W ratios and green spaces to adapt urban climate change. The study focuses on thermal comfort issues of humans in urban areas and performs evaluation in terms of physiologically equivalent temperature (PET), based on long-term data. Meteorological data of air temperature, relative humidity, wind speed and solar radiation over a 7-year period (2003–2010) were used. A 3D street canyon model was designed with RayMan Pro software to simulate the influence of urban configuration on urban thermal climate. The following configurations and setups were used. The model canyon was 500 m in length, with widths 9, 21, and 44 m. Its height varied in steps of 2.5 m, from 5 to 40 m. The canyon could be rotated in steps of 15°. The results show that urban design parameters such as width, height, and orientation modify thermal conditions within street canyons. A northeast–southwest orientation can reduce PET during daytime more than other scenarios. Forestry management and green areas are recommended to promote shade on pedestrian areas and on facades, and to improve bioclimate thermal stress, in particular for H/W ratio less than 0.5. The method and results can be applied by architects and urban planners interested in developing responsive guidelines for urban climate issues.

Assessment of thermal bioclimate and tourism climate potential for central Europe—the example of Luxembourg

Tourism destinations often require information about climate to assess their climate potential. This can be performed in terms of mean conditions of relevant climatological parameters. For a user-friendly analysis and visualization of climate data relevant for tourism application in Luxembourg, information is prepared based on the facets of climate in tourism. Information on thermal comfort/stress conditions as well as aesthetical and physical parameters is considered. In the present study, relevant and sensible factors were identified and presented. Therefore, physiologically equivalent temperature, precipitation patterns and the Climate-Tourism/Transfer-Information-Scheme are applied. In addition, extreme events relevant for heat stress are analysed based on existing data sets (i.e. heat waves of 2010). Expected climatic conditions for the future are investigated using the projections of two different regional climate models. The results concerning climate change conditions reveal increasing heat stress and sultriness but decreasing cold stress. This information is the basis for an adequate assessment to provide relevant information for different environmental planning issues as well as for the growing tourism sector of Luxembourg.

Analysis of thermal bioclimate in various urban configurations in Athens, Greece

The present study deals with human thermal comfort, as it is quantified by two well-known human biometeorological indices, Physiologically Equivalent Temperature (PET) and Humidex, in selected urban areas with different tree and building structures. The study took place during July 2003, at Agricultural University of Athens, Greece. Meteorological and environmental measurements were carried out at six sites. The selected sites differ in regard to sky view factor (SVF) values, environmental configuration and green (vegetation) coverage. The results of this study indicate a striking influence of site config- uration on human thermal comfort. For example, in an outdoor lawn area surrounded by trees (green atrium) the PET was greater than 41 °C (human perception of "very hot") for 13 % of the measurement time, while in an open building atrium (courtyard) PET was greater than 41 °C for 28 % of the time. In addition, 'comfortable' conditions as PET quantifies formed during 26 % of the measurement time in green atrium but less than 15 % of the time in the building atrium. Especially during daytime the difference between these two sites reached 8.7 °C according to the PETand 4.3 °C according to the Humidex. At sites with low SVF values and dense green coverage the human biometeorological conditions were improved compared to sites with high SVF values and those with buildings nearby. Significant relationships between SVF and biometeorological indices classes were indicated. The PET index better represented human comfort than Humidex.

Modeling of changes in thermal bioclimate: examples based on urban spaces in Freiburg, Germany

The Place of the Old Synagogue is a popular place in the city center of Freiburg, a medium-sized city in southwest Germany. It is going to be redesigned soon. In this paper the impact of urban street design and surface material on human thermal comfort is analyzed using the example of the Place of the Old Synagogue. The models SkyHelios, RayMan, and ENVI-met were applied to quantify and qualify the changes. All three models are freely available. Their combination allows analysis of development in long-term conditions, as well as changes in spatial distribution of thermal comfort, as well as of heat stress in summer. Results show that the models can provide valuable information. About the Place of the Old Synagogue, quantitative results show that the period with heat stress will become longer, while the intensity of heat stress increases. The spatial results show that the most significant changes are due to changes in shading. Nevertheless, an increase in thermal stress up to 10 °C is calculated for areas, where ground coverage changes from grass to pavement.

When Stroke Epidemiology Meets Weather and Climate: A Heat Exposure Index from Human Biometeorology

Investigating the relationship of stroke and weather is complex. 11C of air temperature difference in a warm climate may not necessarily mean the same in a cold climate (1). In the thermal environment, in addition to considering air temperature and air humidity, wind speed can reduce the thermal stress conditions and different radiation fluxes can modify the thermal perception directly. Vapour pressure of the surrounding air, which affects human ability to cool down the body through transpiration, is also of importance. The effect of wind velocity becomes stronger when the body is sweating or under cold conditions. Development of adequate methods in assessing the relationship of weather and stroke needs to be locality specific and takes other relevant indicators into account such as physiological, behavioural and other characteristics to reduce ecological bias (2). The concept of physiologically equivalent temperature (PET), as a single thermal index similar to air temperature with a widely known unit, 1C, is used to consider the energy exchange of the human body under the standard conditions in an outdoor setting (3–5). In short, it contains meteorological and thermophysiological parameters described above and was initially created to characterise and evaluate the thermal bioclimate in a physiologically significant manner. It is then assumed that large differences between air temperature and PETmay arise in certain periods of the year such as winter time in the northern hemisphere or summer time in the southern hemisphere (Fig. 1). The application of PET assessment can be carried out by a RayMan model (4). It also helps to assess cold stress (PETo41C), heat stress (PET4351C) and extreme heat stress (PET4411C). This can be linked to assess disease events in extreme weather conditions. With this shared value, pooling worldwide data for meta-analysis can generate valid and reliable comparisons and further assist translating the findings into clinical and other medical practice.

Estimation of the tourism climate in the Hunter Region, Australia, in the early twenty-first century

Existing tourism-related climate information and evaluation are typically based on mean monthly conditions of air temperature and precipitation and do not include thermal perception and other climate parameters relevant for tourists. Here, we quantify climate based on the climate facets relevant to tourism (thermal, physical, aesthetical), and apply the results to the Climate-Tourism-Information-Scheme (CTIS). This paper presents bioclimatic and tourism climatological conditions in the Hunter Region-one of Australia's most popular tourist destinations. In the Hunter Region, generally, temperatures below 15°C occur from April through October, temperatures less than 25°C are expected throughout the whole year, while humidity sits around 50%. As expected, large differences between air temperature and physiologically equivalent temperature (PET) were clearly identified. The widest differences were seen in summer time rather than in the winter period. In addition, cold stress was observed less than 10% of the time in winter while around 40-60% of heat stress was observed in summer time. This correlates with the highest numbers of international visitors, who usually seek a warmer weather, at the beginning of summer time (November and December) and also to the number of domestic visitors, who tend to seek cooler places for recreation and leisure, in late summer (January-March). It was concluded that thermal bioclimate assessment such as PET and CTIS can be applied in the Hunter region, and that local governments and the tourism industry should take an integrated approach to providing more relevant weather and climate information for both domestic and international tourists in the near future.

Climate change and thermal bioclimate in cities: impacts and options for adaptation in Freiburg, Germany

The concept of physiologically equivalent temperature (PET) has been applied to the analysis of thermal bioclimatic conditions in Freiburg, Germany, to show if days with extreme bioclimatic conditions will change and how extreme thermal conditions can be modified by changes in mean radiant temperature and wind speed. The results show that there will be an increase of days with heat stress (PET > 35 degrees C) in the order of 5% (from 9.2% for 1961-1990) and a decrease of days with cold stress (PET < 0 degrees C) from 16.4% to 3.8% per year. The conditions can be modified by measures modifying radiation and wind speed in the order of more than 10% of days per year by reducing global radiation in complex structures or urban areas.

Bioclimatic maps for tourism purposes

Several daily measurements of air temperature, relative humidity, wind velocity and mean cloud cover are required for the calculation of the Physiologically Equivalent Temperature (PET). Using data obtained from daily measurements at 7, 14 and 19 CET over the period from 1991 to 2000 of 201 Austrian climate stations, we analysed the thermal bioclimate in Austria. The calculated PET-values were compared with the results of another computation using synoptic data not only from Austria but also from neighbouring countries. The mean radiant temperature is rather complex, as it covers all relevant short and long-wave radiation fluxes and plays an important role in the energy balance of humans. Based on the individual current conditions, this parameter was calculated using the well-established ‘RayMan’ model, which was development based on guidelines of the German Engineering Society, i.e. VDI 3789 ( VDI, 1994). The mean radiant temperature is determined based on the mean cloud cover and the maximum possible global radiation at a certain time and location. Statistical and GIS methods were used to convert the point-data consisting of PET-values for individual climate stations into a continuous surface. PET was spatially interpolated through a multiple linear regression analysis on a given grid. The results reveal fundamental information which is of particular relevance to the tourism and recreation authorities. The results are also important for spas and wellness resorts.

Effects of a moderate sized city on human thermal bioclimate during clear winter nights.

The human thermal bioclimatic effects of urbanization and natural topographic features (the ocean and hills) were investigated during clear winter nights in Christchurch, New Zealand. Results are presented in terms of the amount of clothing insulation required to balance the body heat budget equation of a standing person with no change in body heat storage. The ordering of urban-rural land use zones from lowest to highest clothing requirements was: CBD, light industrial-commercial, residential and rural. Air temperature accounted for most of the variation in clothing requirement with the model used and weather conditions investigated here followed by environmental thermal radiation. The oceans and hill slopes had an effect comparable to that of most of the urban area and required less clothing than did all land use zones except the urban CBD.