Evaluation of an Urban Canopy Model with Enhanced Hydrologic Processes in a Tropical City: the Role of Tree Evapotranspiration

A single layer urban canopy model (SLUCM) with enhanced hydrologic processes, which has satisfactory simulation of urban surface energy conditions in some urban areas, is now firstly evaluated in a tropical city, Singapore. The evaluation is conducted for an 11-month period in an offline simulation coupling with Noah land surface model in Weather Research and Forecasting (WRF) model at a high-density residential site in Singapore. Results show that the energy fluxes, latent heat flux in particular, have a significant improvement by considering the various hydrologic processes: (1) anthropogenic latent heat release and (2) urban oasis effect. However, simulated latent heat flux is still about 40% underestimated. Considering Singapore’s high green cover ratio, we introduce tree evapotranspiration process into this model. The simulation of latent heat flux further improves towards the observed data. This result suggests that planting trees may be a good way in cooling tropical areas. The roles that various hydrologic processes play in urban surface energy balance are also examined during a particularly dry spell (no precipitation for two months in the rainy season) in Singapore.