Small-scale human-biometeorological impacts of shading by a large tree

• Main Authors: Kántor Noémi, Kovács Attila, Takács Ágnes
• Format: Article
• Language: English
• Published: De Gruyter 2016-04-01
• Series: Open Geosciences
• Subjects: urban tree; shading; heat stress reduction; physiologically equivalent temperature
• Online Access: https://doi.org/10.1515/geo-2016-0021

This study provides evidences on the beneficial small-scale human-biometeorological effects of a large shade tree during the daytime in summer. We carried out detailed measurement from 10 am to 6 pm with two human-biometeorological stations on a popular square in Szeged, Hungary. One of the stations stood under a great Sophora japonica, while the other in the sun. Compared to the sunny location, we found 0.5°C lower air temperature, 2% higher relative humidity and 0.4 hPa higher vapor pressure under the tree. From human-biometeorological point of view, we observed more significant differences. The tree reduced the mean radiant temperature by 22.1°C and the physiological equivalent temperature by 9.3°C - indicating about two categories lower physiological stress on the human body. In order to demonstrate the background mechanisms of these differences, we analyzed separately the components of the radiation budget. The effect of tree crown on radiation components was found to be greater in the short-wave domain than in the long-wave domain. The extended foliage reduced the solar radiation from the upper hemisphere and thus lowered the radiation from the ground (the reflected short-wave and the emitted longwave flux densities) along with the radiation from the lateral directions.