Thermal Environment In Urban Area Research Articles

Evaluation of effect of tree canopy on thermal environment, thermal sensation, and mental state

Greenery is considered an important countermeasure technology that can be used to improve the thermal environment in urban areas. In this study, the effects of environmental factors relating to tree canopies on physiological response and human sensible temperatures were examined. Measurements were analyzed to determine the mutual relationship between the environmental elements of the tree canopy and the physiological response and psychological reaction. In five areas with tree canopies of different forms, located on the Osaka Prefecture University campus, measurements were performed during the hot summer season. The amount of solar radiation in the tree canopy was greatly attenuated in comparison to sunlit locations. In addition, it was determined that the air temperature in the tree canopy was about 1°C lower in sunlit areas. Human thermal load under the tree canopies is closer to neutral than in sunlit places. The blocking of solar radiation greatly affected physiological response. Results of psychological testing confirm the effect of comfort was experienced under tree canopies. However, gloomy impressions were suffered in areas where the leaf area index was large. The fatigue value correlated best with physiological response. It was concluded that the thermal sensation of hot was causing mental fatigue.

Estimating spatial patterns of air temperature at building‐resolving spatial resolution in Seoul, Korea

ABSTRACTThe thermal environment in urban areas is substantially influenced by local surface properties and their modification through human activities. The effects of urban climate on human health are one of the motivations for the development of various urban climate analysis tools. Climate Analysis Seoul (CAS) is a tool that incorporates a meso‐scale atmospheric model and conceptual geographic information system (GIS)‐based models to provide gridded air temperature deviations based on high‐resolution land cover information. The CAS output was evaluated using air temperatures observed at 18 automatic weather stations (AWS) located in the detail region (DR) Eunpyeong. Correlation analyses were performed to reveal the influence of different land cover characteristics and CAS output variables on measured air temperature deviations. Based on the results of the correlation analyses in the study region (SR) Seoul, a regression model (total air temperature distribution, TD′) was developed. It predicts spatially distributed air temperatures based on morphological parameters and an observed reference temperature. Using the TD′ model, maps of daily maximum air temperatures were produced for the entire area of Seoul with a horizontal resolution of 25 m, and of 5 m for the DR, the latter allows to assess the impacts of different building and vegetation structures on air temperature by resolving buildings. The TD′ model was evaluated using measurements at eight AWS. The TD′ model slightly overestimated daily maximum air temperatures in 2007 and 2011, but performed better for 2011, mainly because land cover data represent the final state of the urban development. The TD′ model appears to be a suitable tool for estimating air temperature distributions at building‐resolving resolutions. It can be used to assess changes in the thermal environment and heat‐related hazards through urban development plans already ahead of their realization.

都市環境気候図作成のための街路空間の風環境評価に関する研究

Ventilation in street canyons contributes to mitigation of extremes in the thermal environment in urban areas. In previous studies, a strong relationship between the gross building coverage ratio and the spatial average wind velocity at pedestrian level has been confirmed. In this study, the relationship between wind environment and street canyon characteristics was analyzed using CFD and a GIS tool. Spatial average wind velocity is explained better by the open space ratio rather than the gross building coverage ratio in grids more than 250 m square grid. It means that the open space ratio is more direct indicator to spatial average wind velocity. Spatial average wind velocity averaged in the area of about 250 to 1,250 m square grid is meaningful. In this scale, it is possible to extract the typical characteristics of wind environment in the street canyon. When the evaluation scale is less than 100 m square, the wind environment in street canyons is best evaluated by more specific indicators (e.g., building height and road width) rather than spatially averaged indicators.

安定化有限要素法による都市の温熱環境解析手法の構築

安定化有限要素法による都市の温熱環境解析手法の構築

Impacts of land use and topography on the cooling effect of green areas on surrounding urban areas

Few studies have examined the influence of land use and terrain on the cooling effect of green areas on surrounding urban areas. We investigated the spatial distribution of the cooling effect of green areas on surrounding urban areas in Heiwa Park, Nagoya, central Japan, by applying surface temperature (Ts) information obtained from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image data. The cooling effect was found to extend in many directions into the urban areas. The spatial distribution of Ts showed that commercial areas interrupted the flow of park cooling, whereas other types of urban areas expanded park cooling more effectively. We hypothesise that this was the result of differences in geometric and thermal properties and anthropogenic heat release between commercial and other areas. The spatial distribution of Ts also reflected the effects of topography on park cooling. The green area at our study site was located on a hill, and the downward slope and valley terrain inside the park increased the cooling effect towards the surrounding urban areas. To improve the thermal environment of urban areas and the comfort levels of residents, effective utilisation of the cooling effect of green areas should be incorporated into urban designs that consider the effects of land use and topography.

Summer air temperature distribution and thermal environment in urban areas of Japan

AbstractThe air temperature distribution was measured, and the thermal environment was studied in August (summer season) in an urban area of approximately 10 km × 15 km in Hyogo Prefecture, Japan. We introduced a new index to evaluate the thermal condition. Combining the newly introduced index with other indices enabled us to show the thermal conditions in more detail. The inland thermal conditions were milder than those in the coastal areas when the air temperature was lower than 30 °C. In contrast, the inland thermal conditions were more severe than those in the coastal areas when the air temperature was higher than 30 °C. Copyright © 2008 Royal Meteorological Society

FIELD MEASUREMENTS AND HEAT BUDGET ANALYSIS ON SENSIBLE HEAT FLUX FROM PAVEMENT

The mean air temperature in urban areas has risen due to a change of urban structure in a long term. High reflective paints can reduce a cooling load of buildings and may also improve the thermal environment in urban areas. In this paper, field measurements were carried out on pavement where two areas of surface were coated with high reflective paint and ordinary material. Then, the heat flux on the urban surface was calculated on the basis of heat budget equation with the measured data, and the result was compared with the artificial heat release from buildings etc. in 23 wards of Tokyo. The results of this paper show that high reflective paint is effective to resolve heat island problem.

Effects of Tree Planting on Ventilation and Thermal Environment in Urban Area

Effects of Tree Planting on Ventilation and Thermal Environment in Urban Area

REDUCTION OF SENSIBLE HEAT EMISSION BY INCREASING ROOF SOLAR REFLECTANCE AS A COUNTERMEASURE OF HEAT ISLAND PHENOMENA

The mean air temperature in urban areas has risen due to a change of urban structure in a long term. High reflective paints can reduce a cooling load of buildings and can also improve the thermal environment in urban areas. In this paper, field measurements were carried out in a building where two areas of rooftop were finished with high reflective paint and ordinary paint. Then, the heat flux on the urban surface was calculated on the basis of heat budget equation with measured data, and the result was compared with the artificial heat release from buildings in 23 wards of Tokyo. The results of this paper show that high reflective paint is effective to resolve heat island problem. On the other hand, short wave radiation reflected at high reflective roofs may increase cooling load of neighbor buildings. In this paper, the coupled simulations of radiation and convection around buildings were conducted to estimate the influence of solar reflection at roofs on surrounding building walls. The results show that short wave radiation from high reflective roofs to neighbor building walls is much smaller than direct radiation from sun and sky to walls.

407 人体の温熱快適性に与える衣服素材の影響に関する基礎的研究(省エネルギー(2),環境保全型エネルギー技術)

There is increasing concern about the health effects of the severe thermal environment in urban area. Because of these situations, it is important to estimate the thermal comfort for environmental improvements and designs. For estimating thermal comfort, surrounding environmental components, especially clothing material, are important, because clothing material has an impact on thermal exchange between exterior environment and human body. In this paper, the heat and the moisture transfer properties were examined in various conditions. The heat and the moisture transfer coefficients were calculated from measured values such as mass, temperature and humidity based on heat balance of sensible heat and latent heat. The heat and the moisture transfer coefficients can be obtained at the same time using our own making experimental apparatus. The heat and the moisture transfer coefficients indicate how effectiveness of the velocity of wind, the thickness of clothing material and the differences among fabric were clarified. The radiation properties such as reflectivity, transmissivity and adsorption of clothing were measured. These data are utilized for prediction of human thermal comfort.

Thermal and Geometric Controls on the Rate of Surface Air Temperature Changes in a Medium-Sized, Midlatitude City

Abstract Gradual cooling in the evening forms a wintertime nocturnal urban heat island. This work, with a mesoscale model involving urban canopy physics, is an examination of how four thermal and geometric controls—anthropogenic heat QF, heat capacity C, thermal conductivity k, and sky-view factor ψs—modify the rate of surface air temperature changes ΔT/Δt. In particular, the time dependence is diagnosed through numerical experiments. The controls QF and k are major agents in the evening, when QF changes the evening ΔT/Δt linearly and k is logarithmic. The effects of C and ψs are large in the morning and in the afternoon with those of k. The impact of QF is, however, substantial only in the evening. Because the time dependence of C and k is different, the thermal inertia used as a parameter in the urban climate studies should be divided into two parameters: C and k. To improve the thermal environment in urban areas, the modification of QF and k could be effective.

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling. The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.

05/01365 Regulatory standards related to building energy conservation and indoor-air-quality during rapid urbanization in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.

9032 市街区熱環境の大規模数値解析(GS-D 一般セッション(行列計算))

9032 市街区熱環境の大規模数値解析(GS-D 一般セッション(行列計算))

Mitigation Effects of Thermal Environment of Urban Area by Watering

The social experiment was carried out for the purpose of the mitigation of the heat island effect by watering on August 18th to 25th. The microclimate observation has been carried out at watering area in Eastern Tokyo. As the results, the effect of the watering on the thermal environment in urban area was evaluated as decreasing effect on temperature. The following results were obtained; 1) The temperature variation in the daytime is included to be different every site because of the dispersion of surface temperature. 2) The air temperature in the experiment area is from 2 to 9 [degree] higher than temperature in thermometer shelter by the effect of long radiation. 3) The temperature decrease instantaneously when watering starts. 4) The temperature decreases 0.66 [degree] on average, 1.93 [degree] on maximum after the watering. 5) Total amount of decreasing temperature is decreased linearly by the distance from the point of watering.

Analyses of the Thermal Environment in Urban Area and Its Surrounding

Analyses of the Thermal Environment in Urban Area and Its Surrounding

Analyses of the Thermal Environment in Urban Area and Surrounding

Meteorological field observations were conducted at a small urban area in the lakeshore basin environment in summer. During the daytime of a clear, calm day, about 2000m height of the mixing layer were developed by the thermally induced circulation over the basin. The maximum of air temperature around the lake shore were recorded after 1500LST, and at 1800LST for the urban area. It is conjectured that the mechanism of a continuation of high temperature in urban area is mainly due to the complex factors such as the downward wind which brings high temperature of air mass by the circulations, the relatively high temperature of paved ground and roof surfaces, and the improved mass and heat exchange within and above the urban canopy layer. Numerical simulation was conducted to evaluate these convection and urban effects by a three-dimensional turbulent closure model. The results were in good agreement with observed value of air temperature, mixing ratio, and wind profiles. The large curculation also reproduced well, and it brought warm and dry air mass to the ground over the lake.

DEVELOPMENT OF A COMPUTER-

An analitical system for urban climate is developed with the aid of GeographycalImformation System (GIS) based on personal computers. Basic data necessary for analyzing thermal environment of urban areas are systematically processed, transformed to maps and exhibited on the display. For example, grid data of artificial heat emission from three kinds of sources, i.e., households, business and commercial buildings, and motor vehicles can be visually demonstrated on a map.“Thermal Environmental Diagnosis System” or an expert system to assess thermal structure of towns is also developed and tested for Kumamoto City.

都市の熱環境および緑・植物 （その２） 都市熱環境における植物の役割に関する研究 ＳｉＢモデルに基づく数値シミュレーション

Thermal environment of urban areas is largely determined by the physical structure of their land surface. Green tracts, in particular, play an important role in the heat balance through evapotranspiration. In order to quan tify the role of urban vegetation in the determination of surface temperature, this study conducts numerical simulations based on Simple Biosphere model (SiB) and analyzes the relationship between physical peculiarities of vegetated land surface and temperature distribution. SiB was originally developed for GCMs, in order to calculate the transfer of energy, mass and momentum between the atmosphere and the vegetated surface of the earth. The vegetation in each terrestrial model grid area is represented by two distinct layers. The upper layer represents the perennial canopy of trees or shrubs, and the lower layer represents the annual ground cover of grasses. SiB contains three temperature-related variables, each of which represents the temperatures of different components of the ground surface; i. e., canopy, ground cover and the air space in can opy. Thus the variation of temperatures at different parts of the vegetated ground surface is analyzed and the calculated values are compared with the the brightness temperature measured by remote sensing.

都市の熱環境制御に関する研究 一次元熱収支モデルによる地表面温度とリモセン輝度温度との比較

都市の熱環境制御に関する研究 一次元熱収支モデルによる地表面温度とリモセン輝度温度との比較