How do street trees affect urban temperatures and radiation exchange? Observations and numerical evaluation in a highly compact city

Street trees are an important driver of street microclimate through shading and transpirative cooling, which key mechanisms for improving thermal comfort in urban areas. Urban canopy models (UCM) with integrated useful tools because they represent the impacts on neighborhood-scale climate, resolving interactions between buildings, atmosphere. In this study, we present results a measurement campaign where vehicle transects were completed along two similar parallel streets Barcelona different tree densities, recording upward downward radiation fluxes, air temperature humidity at level. These observations used to evaluate improve multi-layer UCM Building Effect Parameterization Trees (BEP-Tree). Prior simulations model revealed insufficient heat exchange canyon surfaces lowest vertical levels inside deep canyons, solve by including turbulent buoyancy driven wind velocity model. Air temperatures average 1.3 °C higher sparser when direction is perpendicular streets. The BEP-Tree demonstrate good agreement terms radiation, capture diurnal evolution