MLUCM BEP + BEM: an offline one-dimensional multi-layer urban canopy model based on the BEP + BEM scheme

The MLUCM BEP + BEM model advances urban microclimate modelling by combining a multi-layer canopy approach with Building Effect Parameterization (BEP) and a Building Energy Model (BEM). It includes updated turbulent length scales and eddy diffusivity coefficients that account for atmospheric stability, along with explicit representation of urban vegetation, such as street trees and green spaces. The model runs offline with low computational demands, making it suitable for standalone use, integration with climate projections, and long-term simulations to evaluate emission scenarios and adaptation strategies. Validation against data from the Urban-PLUMBER project at a suburban site in Preston (Melbourne, Australia) demonstrates that MLUCM BEP + BEM reliably reproduces shortwave (SWup) and longwave (LWup) radiation, as well as latent (Qle), sensible (Qh), and momentum (Qtau) fluxes. Its overall performance is on par with, and in several cases surpasses, that of other established urban models with particularly notable improvements in the simulation of momentum flux (Qtau). Some refinements are still needed, particularly in modelling tree-soil moisture dynamics to reduce surface energy budget imbalances. Thanks to its flexibility and efficiency, MLUCM BEP + BEM is well-suited for assessing urban overheating, building energy demand, and the effectiveness of mitigation strategies such as green roofs, cool materials, and photovoltaic systems under various future climate scenarios.