EFFECTS OF ROADSIDE TREES ON TURBULENT AIRFLOW, AIR POLLUTANT DIFFUSION AND PEDESTRIAN THERMAL COMFORT WITHIN STREET CANYONS : Field measurements of summer thermal environment and air quality in the central part of Sendai (Part 1)

Abstract

This study aims to clarify the effects of roadside trees on turbulent airflow, air pollutant diffusion and pedestrian thermal comfort within street canyons in the central part of Sendai city, Japan. The detailed measurements were carried out within Jozenji-street in the summer of 2004. Measurements within Hirose-street were also conducted for comparison. Characteristics of flow pattern and distributions of turbulence quantities were investigated, and time-variations of spatial distributions of NO_X concentration and thermal environment, i.e. air temperature, globe temperature, air humidity and SET were shown. In Jozenji-street, many trees were planted on sidewalk and central walkway, and the density of trees was much higher than that in Hirose-street. The effects caused by roadside trees showed complex results which clearly improved thermal environment but also increased NO_X concentration simultaneously.