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Figure from:The urban heat island in Tokyo: a seasonally understanding

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Fig. 14: Temporal variations of the air temperature measured on July, 29th-30th 2002, weekday observation. (Source: BEM; Kikegawa et al., 2006)

Figure 14 Temporal variations of the air temperature measured on July, 29th-30th 2002, weekday observation. (Source: BEM; Kikegawa et al., 2006)

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Furthermore, in 2014 the world’s annual anomaly of the global average surface temperature was +0,27°C above the 1891-2010 average, making it the warmest year since 1891, but the annual mean temperature over Japan was normal. This is to be nuanced by the following statements: above-normal temperature were experienced in all regions for several months, but temperatures fluctuated periodically with largely bellow- normal temperature periods. Typhoons and developed cyclones due to migratory high pressure systems were dominant and brought in spring and autumn long sunshine hours to northern and eastern Japan as well as high precipitation amounts (Fujikawa, 2015).
Furthermore, in 2014 the world’s annual anomaly of the global average surface temperature was +0,27°C above the 1891-2010 average, making it the warmest year since 1891, but the annual mean temperature over Japan was normal. This is to be nuanced by the following statements: above-normal temperature were experienced in all regions for several months, but temperatures fluctuated periodically with largely bellow- normal temperature periods. Typhoons and developed cyclones due to migratory high pressure systems were dominant and brought in spring and autumn long sunshine hours to northern and eastern Japan as well as high precipitation amounts (Fujikawa, 2015).
Fig. 4: Number of days with daytime temperature above 30°C. Plus 10 days in 30 years. (Source: Ando Haruo, Kibankenkyu, 2006) Observations on a thirty year period reveal other valuable data of temperature anomalies in Tokyo. Days with temperatures above 30°C have increased by 10 on average between 1970 and 2000 and nights with minimum temperature above 25°C by 17 days as shown in Fig. 4 and Fig. 5 (measurements made in Otemachi, Tokyo).
Fig. 4: Number of days with daytime temperature above 30°C. Plus 10 days in 30 years. (Source: Ando Haruo, Kibankenkyu, 2006) Observations on a thirty year period reveal other valuable data of temperature anomalies in Tokyo. Days with temperatures above 30°C have increased by 10 on average between 1970 and 2000 and nights with minimum temperature above 25°C by 17 days as shown in Fig. 4 and Fig. 5 (measurements made in Otemachi, Tokyo).
The canopy roughness of centre Tokyo hinders ventilation, resulting in lower efficiency of the near-surface heat diffusion. The urban canyons also weakens cooling by radiation emissions during night hours because of the reduced sky view factor. To those heat-trapping effects can be added the waste heat emission of air- conditioners, energy-consuming equipments and automobiles that cannot be underestimated in the densely populated city centre. Those factors contributes in varying degrees to the formation of the urban heat island .
The canopy roughness of centre Tokyo hinders ventilation, resulting in lower efficiency of the near-surface heat diffusion. The urban canyons also weakens cooling by radiation emissions during night hours because of the reduced sky view factor. To those heat-trapping effects can be added the waste heat emission of air- conditioners, energy-consuming equipments and automobiles that cannot be underestimated in the densely populated city centre. Those factors contributes in varying degrees to the formation of the urban heat island .
Fig. 5: Number of days with night temperature above 25°C. Plus 17 days in 30 years. (Source: Ando Haruo, Kibankenkyu, 2006)
Fig. 5: Number of days with night temperature above 25°C. Plus 17 days in 30 years. (Source: Ando Haruo, Kibankenkyu, 2006)
Residents of Tokyo are being exposed to higher temperatures during longer hours than before. The intensive UH nig lac ht cooling of buildings. The longer than norma k of evaporative cooling opportunities and I effect in summer diminishes diurnal temperature differences and have negative effects on the potential sunshine duration, the high built density of the city, the the high thermal mass of the concrete and asphalt environment is translated in a growing thermal discomfort. Higher daytime temperatures mean a greater use of air-conditioning and equipment use. The dai dif This vicious circle continuously increases anthro temperatures. y accumulated heat by the built environment is more ficultly released on the nighttime where the city dwellers continue using their air-conditioning system. pogenic heat emissions which causes additional rise of Fig. 6: Number of days with minimum temperatures under 0°C, Otemachi, Tokyo. (Source: Ando Haruo, Kibankenkyu, 2006)
Residents of Tokyo are being exposed to higher temperatures during longer hours than before. The intensive UH nig lac ht cooling of buildings. The longer than norma k of evaporative cooling opportunities and I effect in summer diminishes diurnal temperature differences and have negative effects on the potential sunshine duration, the high built density of the city, the the high thermal mass of the concrete and asphalt environment is translated in a growing thermal discomfort. Higher daytime temperatures mean a greater use of air-conditioning and equipment use. The dai dif This vicious circle continuously increases anthro temperatures. y accumulated heat by the built environment is more ficultly released on the nighttime where the city dwellers continue using their air-conditioning system. pogenic heat emissions which causes additional rise of Fig. 6: Number of days with minimum temperatures under 0°C, Otemachi, Tokyo. (Source: Ando Haruo, Kibankenkyu, 2006)
Fig. 7: An Example of the Results of Evaluation of Environment-Conscious Measures in Office Buildings (Source: TMG, 2005) (Urban and Global Environment Division Bureau of the Environment, TMG, 2005) Buildings have tremendous impacts on the environment, such as heavy consumption of resources and energy and a depletion of greeneries, while being constructed and operated. The Tokyo Green Building Program is designed to require building owners to care about the environment in newly constructing or expanding large buildings in four areas, which are “rational use of energy,” “optimum use of WM. resources,” “preservation of the natural environment,” and “mitigation of the heat island phenomenon.”
Fig. 7: An Example of the Results of Evaluation of Environment-Conscious Measures in Office Buildings (Source: TMG, 2005) (Urban and Global Environment Division Bureau of the Environment, TMG, 2005) Buildings have tremendous impacts on the environment, such as heavy consumption of resources and energy and a depletion of greeneries, while being constructed and operated. The Tokyo Green Building Program is designed to require building owners to care about the environment in newly constructing or expanding large buildings in four areas, which are “rational use of energy,” “optimum use of WM. resources,” “preservation of the natural environment,” and “mitigation of the heat island phenomenon.”
This tend to result in environmentally unfriendly medium rise buildings widespread across the city, build mostly by contractors roughly adapting existing design schemes to a particular site and client. Poor environmental measures are undertaken on top of the regulatory restrictions: this is partially reflected by the “chaotic” yet admired architecture of Tokyo, where each building is totally independent from the other and its context, and where no outer walls touch another. Medium rise office buildings of generally 8 to 12 floors are highly glazed on the street facing facades, unshaded, have an exposed thermal mass, are heavily equipped with air conditioners and lighting systems.
This tend to result in environmentally unfriendly medium rise buildings widespread across the city, build mostly by contractors roughly adapting existing design schemes to a particular site and client. Poor environmental measures are undertaken on top of the regulatory restrictions: this is partially reflected by the “chaotic” yet admired architecture of Tokyo, where each building is totally independent from the other and its context, and where no outer walls touch another. Medium rise office buildings of generally 8 to 12 floors are highly glazed on the street facing facades, unshaded, have an exposed thermal mass, are heavily equipped with air conditioners and lighting systems.
The study case describes the change of thermal environment on the new avenue development separating the congesting urban space of relatively small office buildings in the behind area by a slit between skyscrapers (Fig. 9). The mass of heated air with low velocity staying behind the towers may be cooled, separated and flown away. A numerical simulation was applied using a personal computer, the computation domain was set to 0.6km > 0.6km with a 5 meters grid. The avenue width is 40 meters and the building on both sides assumed to bi reconstructed with the avenue development have a height of 60 meters.
The study case describes the change of thermal environment on the new avenue development separating the congesting urban space of relatively small office buildings in the behind area by a slit between skyscrapers (Fig. 9). The mass of heated air with low velocity staying behind the towers may be cooled, separated and flown away. A numerical simulation was applied using a personal computer, the computation domain was set to 0.6km > 0.6km with a 5 meters grid. The avenue width is 40 meters and the building on both sides assumed to bi reconstructed with the avenue development have a height of 60 meters.
vicious cycle is especially present in the hot and humid summer of Tokyo in East Japan. in fig. 11 average maximum daily and minimum nocturne temperatures can be observed for the period oetween July, 20th 2002 and August, 31st 2002. The highest daily temperatures can be identified mainly as he high density office districts, with a concentration in West Tokyo in the Nakano and Shinjuku districts, where high rises offices and commercial buildings are regrouped, as well as the Ueno area in North-East [okyo. The higher built density of those areas and the daytime use of those buildings are directly expressed n higher daytime temperatures. The correlation between building energy demand, mainly assumed for cooling, and higher air temperature as been studied by several universities and institutes in Tokyo and across Tapan.
vicious cycle is especially present in the hot and humid summer of Tokyo in East Japan. in fig. 11 average maximum daily and minimum nocturne temperatures can be observed for the period oetween July, 20th 2002 and August, 31st 2002. The highest daily temperatures can be identified mainly as he high density office districts, with a concentration in West Tokyo in the Nakano and Shinjuku districts, where high rises offices and commercial buildings are regrouped, as well as the Ueno area in North-East [okyo. The higher built density of those areas and the daytime use of those buildings are directly expressed n higher daytime temperatures. The correlation between building energy demand, mainly assumed for cooling, and higher air temperature as been studied by several universities and institutes in Tokyo and across Tapan.
A dependency analysis of surface air temperature on the urban canopy structure was underta period of July, 26th 2002 to August, Ist 2002 by Kikegawa, Ohashi and Kondo (2007). The diurnal and nocturnal mean values of observed surface temperatures were calculated for each wards area their relation with the areal average value of the sky view factor (calculated for urban d 500m*500m grid where each ward was additionally clarified. As a res view factor as an index of the loca weather station are located). The dominant building type ult, diurnal mean temperature showed no obvious dependency on the s ken for the tl istricts of tl of Tokyo, anc ne ne for each ward canopy structure: larger scale meteorological effects caused Ss by prevailing winds or unstable conditions in the boundary layer explain this observation. In contrast, nocturnal mear temperatures revealed systematic Also to be noted, the nocturnal de dependency as they increase with small sky view factor urban canopies pendency was found to be more remarkable under canopies composed o: exposed concrete constructions with larger heat capacities in offices, residential and commercial areas. The daily stored heat of those buildings is more difficultly released in a tight urban context, translated into a low night cooling capacity and thus higher daily cooling loads. Fig. 12: The derived indices of canopy structure for each 500m grids. (Source: Kikegawa, Ohashi, Kondo, 2007) Fig. 13: The heat budget between the building inside and outside as calculated with the building energy model (Source: BEM; Kikegawa et al., 2006)
A dependency analysis of surface air temperature on the urban canopy structure was underta period of July, 26th 2002 to August, Ist 2002 by Kikegawa, Ohashi and Kondo (2007). The diurnal and nocturnal mean values of observed surface temperatures were calculated for each wards area their relation with the areal average value of the sky view factor (calculated for urban d 500m*500m grid where each ward was additionally clarified. As a res view factor as an index of the loca weather station are located). The dominant building type ult, diurnal mean temperature showed no obvious dependency on the s ken for the tl istricts of tl of Tokyo, anc ne ne for each ward canopy structure: larger scale meteorological effects caused Ss by prevailing winds or unstable conditions in the boundary layer explain this observation. In contrast, nocturnal mear temperatures revealed systematic Also to be noted, the nocturnal de dependency as they increase with small sky view factor urban canopies pendency was found to be more remarkable under canopies composed o: exposed concrete constructions with larger heat capacities in offices, residential and commercial areas. The daily stored heat of those buildings is more difficultly released in a tight urban context, translated into a low night cooling capacity and thus higher daily cooling loads. Fig. 12: The derived indices of canopy structure for each 500m grids. (Source: Kikegawa, Ohashi, Kondo, 2007) Fig. 13: The heat budget between the building inside and outside as calculated with the building energy model (Source: BEM; Kikegawa et al., 2006)
Fig. 16: Regional classification of diurnal change in spatial anomalies of temperature in summer. a) indicates distribution of observation stations classified in 6 clusters. Squares denote observation stations. Each colour corresponds to each cluster number. b) — f) indicate the diurnal variations in spatial anomalies of temperature averaged in each cluster. Six colours and numbers in b) — f) correspond to each cluster. (Source: Akasaka, Ando, Yokoyama, 2009) A research held by the Tokyo Metropolitan Research Institute for Environmental Protection in 200 investigates the regional characteristics on diurnal change of temperature in the greater Tokyo and puts int relation the urban heat island human factors and the climatic ones, such as the sea breeze. To study diurna changes of averaged temperature in winter (months of December, January and February), hourly meat temperature were collected from stations dispatched across the city wards for three years from July 2002 t March 2005. Spatial anomalies were also calculated on each station to clarify the regional differences.
Fig. 16: Regional classification of diurnal change in spatial anomalies of temperature in summer. a) indicates distribution of observation stations classified in 6 clusters. Squares denote observation stations. Each colour corresponds to each cluster number. b) — f) indicate the diurnal variations in spatial anomalies of temperature averaged in each cluster. Six colours and numbers in b) — f) correspond to each cluster. (Source: Akasaka, Ando, Yokoyama, 2009) A research held by the Tokyo Metropolitan Research Institute for Environmental Protection in 200 investigates the regional characteristics on diurnal change of temperature in the greater Tokyo and puts int relation the urban heat island human factors and the climatic ones, such as the sea breeze. To study diurna changes of averaged temperature in winter (months of December, January and February), hourly meat temperature were collected from stations dispatched across the city wards for three years from July 2002 t March 2005. Spatial anomalies were also calculated on each station to clarify the regional differences.
Fig. 17: Spot measurements locations. (Source: by the author) After the previous literature researches about the UHI in Tokyo in winter and summer with the daily spatial different temperature anomalies and causes, it is of interest to study the mid-seasons where lower heating and cooling energy loads should be noticed.
Fig. 17: Spot measurements locations. (Source: by the author) After the previous literature researches about the UHI in Tokyo in winter and summer with the daily spatial different temperature anomalies and causes, it is of interest to study the mid-seasons where lower heating and cooling energy loads should be noticed.
Fig. 18: Graphic representation of the spot measurement data. (Source: by the author)
Fig. 18: Graphic representation of the spot measurement data. (Source: by the author)
Fig. 19: Data loggers measurements locations. (Source: by the author) Those measurements reflects the previously studied influence of the urban fabric and human activities on the city’s climate. Further measurements were then taken by data loggers in two points of Tokyo showing great differences in the urban and social density, as well as location and environment: the office and commercial district of Shinjuku and the low-rise residential area of Kiyosumi-shirakawa, situated on the coastal region.
Fig. 19: Data loggers measurements locations. (Source: by the author) Those measurements reflects the previously studied influence of the urban fabric and human activities on the city’s climate. Further measurements were then taken by data loggers in two points of Tokyo showing great differences in the urban and social density, as well as location and environment: the office and commercial district of Shinjuku and the low-rise residential area of Kiyosumi-shirakawa, situated on the coastal region.
The data as been plotted into a graph to have a clear visibility of different results (fig. 20). Predicted daily temperatures from JMA are also figuring. The different microclimate are obvious as well as the difference of regularity. Fig. 20: Graphic representation of the data loggers measurement data. (Source: by the author)
The data as been plotted into a graph to have a clear visibility of different results (fig. 20). Predicted daily temperatures from JMA are also figuring. The different microclimate are obvious as well as the difference of regularity. Fig. 20: Graphic representation of the data loggers measurement data. (Source: by the author)