Abstract
We focused on thermal smartphone infrared cameras, which have become widely available, and used them to photograph trees in parks and green spaces. A total of 196 trees were photographed at two study sites in Japan's eastern and western regions at two different times of the day: daytime and evening. In this study, we inferred the relationship between crown radiant temper ature and various factors, including leaf density, tree shape, tree height, life form, and species, based on daytime survey results. Compared to the daytime air temperature, at the Western site, both tall trees and mid-to-low trees had crown surface temperatures about 1–3°C higher than the air temperature. Mid-to-low trees had higher radiant temperatures than tall trees, and sun-exposed sides were hotter than shaded sides, supporting the influence of radiation temperature that people are likely to perceive in daily life. On the other hand, at the eastern site, since there was no significant difference, the crown surface temperature on the shaded side was lower than the air temperature. By Phenotypic classification, at the western site, the crown surface temperatures of both tall and mid-to-low evergreen broadleaf trees were higher than the air temperature, with the difference being larger for mid-to-low trees on both sun-exposed and shaded sides. For mid-to-low trees, the air temperature difference for conifers was even smaller.
