Effects of roadside trees on the thermal environment within a street canyon

In this paper, the micro-climate and the sensible heat flux in a street with thick tree crowns was investigated from a series of observations during summer. The difference of air temperature is negligible throughout the day compared to a parallel street without tree crowns. However, for the radiation field, there is a clear shielding effect for solar radiation and downward long wave radiation, consequently the road surface temperature will differ. The sensible heat flux at three meters height above the road surface was measured by scintillation method. The heat flux in the street with tree crowns was similar to that without tree crowns, although there was a large difference in road surface temperature between them. The estimated exhaust heat was extremely large and the measured heat flux was dominated by this artificial heat flux. Such a large exhaust heat could partly be explained by the parked vehicles in both sides of the roadway which would keep the air conditioning running