The Building Effect Parameterization with Trees (BEP-Tree) is used here to model the impact of trees on the energy balance of a street canyon during heat wave conditions. BEP-Tree is a neighbourhood-scale multi-layer urban canopy model (UCM) that explicitly includes the interactions between vegetation and built elements in a street canyon. We have implemented an advanced stomatal conductance model in BEP-Tree in order to consider the effects of environmental conditions (air temperature and humidity), soil moisture and vegetation species on transpiration.
The sensitivity of the canyon energy balance to tree transpiration controlling factors is estimated using observations from recent heat wave events in Switzerland. Flux measurements are used to assess the performance of the improved model. The results of this study show the importance of using an advanced stomata model in urban canyon energy balance modelling for street canyons with trees.