Journal of the Human-Environment System
Online ISSN : 1349-7723
Print ISSN : 1345-1324
ISSN-L : 1345-1324
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  • Tsuyoshi Hashimoto, Shinichi Watanabe
    2021 Volume 23 Issue 2 Pages 59-70
    Published: 2021
    Released: March 20, 2021
    JOURNAL FREE ACCESS

    Traditional settlements have been formed by adapting to local climate and natural features. This study aims to clarify the climatic characteristics of a settlement with a group of wooden storehouses in summer daytime from the viewpoint of environmental design. Waniura settlement in Tsushima Island, Japan was selected as the observation site of this study. The largest group of wooden storehouses in Tsushima Island is in Waniura settlement, and it is in the north of the settlement. About 150 storehouses are located near the port. The microclimate observations in the settlement and heat parameters measurements, including UV intensities at three representative points, were carried out in the summer of 2019. The wind direction in the northern part of the settlement had a different trend than that in the sky. The wind directions in Waniura settlement is affected by the topography when the wind in the sky blows in different directions from the valley line in the settlement. The layout of storehouses affects the wind environment of the group of wooden storehouses and the wind reducing effect appears when the wind blows orthogonally to the parallel storehouses. At the shaded path (point-C) on 1,000 W/m2 global solar radiation, the MRT reduction was -25.7 °C. The reason the MRT at the shaded path dropped significantly was that the storehouses built close to each other blocked the solar radiation on the shaded path significantly. Furthermore, less solar radiation on the shaded path might contribute to maintaining the low surface temperatures of the pathway and the storehouses. At the shaded path on 1,000 W/m2 global solar radiation, the UTCI reduction was -4.4 °C. This result emphasizes the importance of providing shade from buildings or other means and directing wind into those spaces to improve the outdoor thermal environment. At the shaded path in the group of wooden storehouses on 1000 W/m2 global solar radiation, the UV Index reduction was -5.4. This large UV Index reduction at the shaded path can be because the storehouses were built close to each other, thus blocking most direct and diffuse components of UV radiation. It has become clear that a heat island appears in the centre of the settlement with a population of about 200 people in the daytime on a clear summer day. In contrast, the heat island did not appear in the group of wooden storehouses, despite the dense construction of storehouses. This is probably because the storehouse is a low-rise wooden building with low heat capacity and because there is no energy consumption or waste heat there. It is evident that the cooling effect of the group of storehouses on the radiant environment, thermal environment and UV environment appears in the summer daytime. Based on the results of the field observations, it has been empirically shown that it is an effective environmental design method for mitigating the thermal environment in the summer daytime by composing a group of low-rise wooden buildings is concerned with taking into account their ventilation.

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  • Tsuyoshi Hashimoto, Jin Ishii
    2021 Volume 23 Issue 2 Pages 71-85
    Published: 2021
    Released: March 20, 2021
    JOURNAL FREE ACCESS

    In the Amami Islands, an original culture has been created and is still maintained. This study focused on the fields with Cycas hedges called “Sotetsu-Bate”, which means “fields with Cycas hedges”, in the Amami Islands. Sotetsu-Bate had established as a locality and specific cultural landscape, in order to protect farm products from wind and seawater. The objective of the present study is to clarify the effects of Cycas hedges on the thermal environment in the fields. Field observations of air temperature, humidity, wind direction, wind velocity, and solar and long-wave radiation were carried out in and around the fields with Cycas hedges in the Kasari area, Amami City, Amami-Oshima.

    In summer and winter, the wind reducing effect of Cycas hedges appeared in the field with Cycas hedges, and it is an effective countermeasure against damage of strong wind and seawater. The wind reducing effect of Cycas hedges against seasonal wind is particularly significant. It is cleared that wind velocity in the field with Cycas hedges was decreased with about 20% of that at the sandy shore, on average. The wind reducing effect of Cycas hedges did not appear clearly at observation points on the north-south main road, compared with the results of observation points in the field with Cycas hedges. This north-south main road was narrower in the old days. It is considered that the wind reducing effect in the fields with Cycas hedges was decreased by road extension.

    In winter and in the early morning of summer, the difference in air temperature, vapor pressure, and relative humidity in the observation site was small. In the daytime of summer, air temperature at observation points in the fields with Cycas hedges was higher than that at the sandy shore in many cases. It is considered that the outdoor sensible temperature formed in the fields with Cycas hedges is very hot and dangerous for human health in the daytime of summer because the air temperature is high and wind velocity is calm or very light. It is advisable to eschew a work in the fields with Cycas hedges in the daytime of summer.

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