Abstract:The mean radiant temperature (T mrt ) is one of the most important meteorological parameters governing human energy balance. In this paper, three different methods of obtaining the T mrt in an outdoor urban setting are compared. Method A is based on integral radiation measurements and angular factors, method B is based on measurements with a 38-mm flat grey globe thermometer and in method C makes use of the Rayman 1.2 software is used. Measurements were performed in a large open square in a high latitude city -Göteborg, Sweden -during clear to overcast weather conditions in October 2005 and in July and August 2006.Results show that the difference between Method A and Method B was generally relatively small. Most of the discrepancy, caused by rapid changes in radiation, temperature and wind speed was smoothed out using 5 min mean values. By systematically and empirically changing the mean convection coefficient, the accuracy of Method B was improved and a new equation expressing the T mrt was obtained. With this new equation the 38 mm flat grey globe thermometer could successfully be used to estimate the T mrt in an outdoor urban setting provided that the wind speed and the air and globe temperatures are measured accurately. The study also shows that the flat grey colour of the globe thermometer slightly underestimates the level of short-wave radiation (i.e. sunshine). Method C works very well during the middle of the day in July, i.e. at high sun elevations. However, the model considerably underestimates the T mrt in the morning and evening in July and during the whole day in October, i.e. at low sun elevations.In outdoor urban settings where thermal comfort researchers or urban planners and designers require an easy and reliable method of estimating mean radiant temperature, the 38 mm flat grey globe thermometer provides a good and cheap solution.
ABSTRACT:The large scale urban consumption of energy (LUCY) model simulates all components of anthropogenic heat flux (Q F ) from the global to individual city scale at 2.5 × 2.5 arc-minute resolution. This includes a database of different working patterns and public holidays, vehicle use and energy consumption in each country. The databases can be edited to include specific diurnal and seasonal vehicle and energy consumption patterns, local holidays and flows of people within a city. If better information about individual cities is available within this (open-source) database, then the accuracy of this model can only improve, to provide the community data from global-scale climate modelling or the individual city scale in the future. The results show that Q F varied widely through the year, through the day, between countries and urban areas. An assessment of the heat emissions estimated revealed that they are reasonably close to those produced by a global model and a number of small-scale city models, so results from LUCY can be used with a degree of confidence. From LUCY, the global mean urban Q F has a diurnal range of 0.7-3.6 W m −2 , and is greater on weekdays than weekends. The heat release from building is the largest contributor (89-96%), to heat emissions globally. Differences between months are greatest in the middle of the day (up to 1 W m −2 at 1 pm). December to February, the coldest months in the Northern Hemisphere, have the highest heat emissions. July and August are at the higher end. The least Q F is emitted in May. The highest individual grid cell heat fluxes in urban areas were located in
The mean radiant temperature, T(mrt), 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. In this paper, a new radiation model (SOLWEIG 1.0), which simulates spatial variations of 3D radiation fluxes and T(mrt) in complex urban settings, is presented. The T(mrt) is derived by modelling shortwave and longwave radiation fluxes in six directions (upward, downward and from the four cardinal points) and angular factors. The model requires a limited number of inputs, such as direct, diffuse and global shortwave radiation, air temperature, relative humidity, urban geometry and geographical information (latitude, longitude and elevation). The model was evaluated using 7 days of integral radiation measurements at two sites with different building geometries--a large square and a small courtyard in Göteborg, Sweden (57 degrees N)--across different seasons and in various weather conditions. The evaluation reveals good agreement between modelled and measured values of T(mrt), with an overall good correspondence of R (2) = 0.94, (p < 0.01, RMSE = 4.8 K). SOLWEIG 1.0 is still under development. Future work will incorporate a vegetation scheme, as well as an improvement of the estimation of fluxes from the four cardinal points.
Subjective thermal comfort and outdoor activity in a park and a square in a satellite city northeast of Tokyo were investigated through structured interviews, observations, and comprehensive micrometeorological measurements. Results showed that the park was on an average 1.1°C cooler than the square. The relatively warmer thermal conditions in the square in comparison to the park resulted in a heat load of greater intensity for humans in the square. In general, there was a low relation between the thermal environment and the use of the two places in terms of total attendance. However, the use of the park was influenced more by the thermal conditions than by the use of the square, which can mainly be attributed to the different functions of the two places. Finally, examples of the differences between the use of the sun, the attitudes toward it, and outdoor exposure in Japan and Sweden are highlighted and discussed.
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