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- Author or Editor: Hiroshi Yoshikado x
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Abstract
A series of observations of the three-dimensional wind and thermal structure of the boundary layer was carried out during each summer season from 1986 to 1988 over the western portion of the Kanto plain. The data obtained during five selected days were analyzed, focusing on the sea breeze system which advances north-westward from Tokyo Bay through the Tokyo metropolitan area.
A distinct sea breeze front was found on three of the days examined, whereas no front was observed during the remaining two days. The difference in the synoptic weather conditions between the frontal and non-frontal days was small, although a definite difference was found in the convective-scale thermal structure.
Temporal and spatial interpolation methods followed by an adjustment using a variational analysis technique were applied to analyze the three-dimensional wind distribution. Trajectories of air parcels wore examined, based on the interpolated wind held.
As a result, it was found that, for the frontal case, the upward motion at the leading edge of the sea breeze subsequently flowed upward over the stagnant region in the suburban are under the influence of the synoptic-scale onshore wind. This stagnant region persisted for a few hours, contributing greatly to the intensification of the front For the non-frontal days, upward flow was found over the urban area during the morning, but it readily diminished.
Abstract
A series of observations of the three-dimensional wind and thermal structure of the boundary layer was carried out during each summer season from 1986 to 1988 over the western portion of the Kanto plain. The data obtained during five selected days were analyzed, focusing on the sea breeze system which advances north-westward from Tokyo Bay through the Tokyo metropolitan area.
A distinct sea breeze front was found on three of the days examined, whereas no front was observed during the remaining two days. The difference in the synoptic weather conditions between the frontal and non-frontal days was small, although a definite difference was found in the convective-scale thermal structure.
Temporal and spatial interpolation methods followed by an adjustment using a variational analysis technique were applied to analyze the three-dimensional wind distribution. Trajectories of air parcels wore examined, based on the interpolated wind held.
As a result, it was found that, for the frontal case, the upward motion at the leading edge of the sea breeze subsequently flowed upward over the stagnant region in the suburban are under the influence of the synoptic-scale onshore wind. This stagnant region persisted for a few hours, contributing greatly to the intensification of the front For the non-frontal days, upward flow was found over the urban area during the morning, but it readily diminished.
Abstract
Intense summer heat in Tokyo, Japan, and its suburban areas between 1990 and 2010 was statistically analyzed. Sample days were selected from among days with a sea breeze and sufficient sunshine duration, because sea breeze is the dominant summertime meteorological system in the region. Excess in the daily maximum temperature of an inland urban site in Tokyo over a site facing the outer sea where the sea breeze originates was selected as a key index. A comparison of a group of days for which the temperature excess was large with an opposing group of days for which it was small revealed a distinct difference in diurnal wind variations: persistent southwesterly winds overwhelmed the sea breeze in areas facing the outer sea in the former case, whereas in the latter case a diurnal sea-breeze cycle was typically observed in those areas as well as in the inland areas. This difference could furthermore be connected to differences in the pressure gradient in the region, that is, differences in the synoptic-scale pressure field. As a result, slight shifts in the pressure field affect urban heat, suggesting that, in addition to general warming, changes in the pressure field resulting from future climate change can be of great importance.
Abstract
Intense summer heat in Tokyo, Japan, and its suburban areas between 1990 and 2010 was statistically analyzed. Sample days were selected from among days with a sea breeze and sufficient sunshine duration, because sea breeze is the dominant summertime meteorological system in the region. Excess in the daily maximum temperature of an inland urban site in Tokyo over a site facing the outer sea where the sea breeze originates was selected as a key index. A comparison of a group of days for which the temperature excess was large with an opposing group of days for which it was small revealed a distinct difference in diurnal wind variations: persistent southwesterly winds overwhelmed the sea breeze in areas facing the outer sea in the former case, whereas in the latter case a diurnal sea-breeze cycle was typically observed in those areas as well as in the inland areas. This difference could furthermore be connected to differences in the pressure gradient in the region, that is, differences in the synoptic-scale pressure field. As a result, slight shifts in the pressure field affect urban heat, suggesting that, in addition to general warming, changes in the pressure field resulting from future climate change can be of great importance.
Abstract
A wintertime small-scale sea breeze associated with high levels of air pollution is described, in which the urban heat island plays an important role.
Over a major portion of the Kanto plain, the winter surface air temperature varies diurnally, ranging from 0° to 12°C on average. The water temperature in the innermost part of Tokyo Bay, surrounded by the plain, is maintained at 8°–10°C. The land–sea temperature contrast that generates sea breezes, however, is intensified by two processes: (i) the heat island associated with the Tokyo metropolitan area on the northwestern shore of the bay increases the land air temperature, and (ii) the nocturnal outflow of cool land air, the result of radiative cooling, covers the bay, causing the sea air temperature to be lower than the water temperature during the morning hours. As a result, the sea breeze frequently penetrates into the heavily urbanized area, extending about 20 km from the bayshore.
Since the sea breeze is coupled with the heat island, it does not penetrate farther inland. A convergence zone persists over the urbanized area, which in turn results in very high concentrations of pollutants.
An analysis of a typical episode is also discussed to more realistically describe the behavior of air pollution than for the averaged case.
Abstract
A wintertime small-scale sea breeze associated with high levels of air pollution is described, in which the urban heat island plays an important role.
Over a major portion of the Kanto plain, the winter surface air temperature varies diurnally, ranging from 0° to 12°C on average. The water temperature in the innermost part of Tokyo Bay, surrounded by the plain, is maintained at 8°–10°C. The land–sea temperature contrast that generates sea breezes, however, is intensified by two processes: (i) the heat island associated with the Tokyo metropolitan area on the northwestern shore of the bay increases the land air temperature, and (ii) the nocturnal outflow of cool land air, the result of radiative cooling, covers the bay, causing the sea air temperature to be lower than the water temperature during the morning hours. As a result, the sea breeze frequently penetrates into the heavily urbanized area, extending about 20 km from the bayshore.
Since the sea breeze is coupled with the heat island, it does not penetrate farther inland. A convergence zone persists over the urbanized area, which in turn results in very high concentrations of pollutants.
An analysis of a typical episode is also discussed to more realistically describe the behavior of air pollution than for the averaged case.
Abstract
A coupled model consisting of a multilayer urban canopy model and a building energy analysis model has been developed to investigate the diurnal variations of outdoor air temperature in the office areas of Tokyo, Japan. Observations and numerical experiments have been performed for the two office areas in Tokyo. The main results obtained in this study are as follows. The coupled model has accurately simulated the air temperature for a weekday case in which released waste heat has been calculated from the energy consumption and cooling load in the buildings. The model has also simulated the air temperature for a holiday case. However, the waste heat from the buildings has little influence on the outdoor temperatures and can be neglected because of the low working activity in the buildings. The waste heat from the air conditioners has caused a temperature rise of 1°–2°C or more on weekdays in the Tokyo office areas. This heating promotes the heat-island phenomenon in Tokyo on weekdays. Thus, it is shown that the energy consumption process (mainly with air conditioning) in buildings should be included in the modeling of summertime air temperature on weekdays in urban areas.
Abstract
A coupled model consisting of a multilayer urban canopy model and a building energy analysis model has been developed to investigate the diurnal variations of outdoor air temperature in the office areas of Tokyo, Japan. Observations and numerical experiments have been performed for the two office areas in Tokyo. The main results obtained in this study are as follows. The coupled model has accurately simulated the air temperature for a weekday case in which released waste heat has been calculated from the energy consumption and cooling load in the buildings. The model has also simulated the air temperature for a holiday case. However, the waste heat from the buildings has little influence on the outdoor temperatures and can be neglected because of the low working activity in the buildings. The waste heat from the air conditioners has caused a temperature rise of 1°–2°C or more on weekdays in the Tokyo office areas. This heating promotes the heat-island phenomenon in Tokyo on weekdays. Thus, it is shown that the energy consumption process (mainly with air conditioning) in buildings should be included in the modeling of summertime air temperature on weekdays in urban areas.
