Efficiently Representing Thermal Processes in Urban Canopy Models

The task of modelling urban environments is challenging because each city is made up of a complex patchwork of structures and materials that dynamically interact with the atmosphere. Urban canopy models must be detailed enough to capture important physical phenomena, but simple enough so that computation can be completed within reasonable timeframes. Clever abstractions allow simple model environments to reasonably represent the complexity of urban climates. However, the act of abstraction, simplification and omissions means model performance may rely on unrealistic model parameters. For example, model performance can degrade if observed physical quantities for thermal characteristics of roofs and walls are used. This poses problems for studies that wish to ascertain the impact of future change to urban form or materials.

In this talk we present our current research revisiting representations in an urban street canyon model. We implement an alternative conduction scheme that improves the representation of heat storage and overall model performance for a wide variety of realistic and optimised walls and roofs. We also discuss current progress in representing internal thermal processes within buildings, which processes are important for the external climate, and the effects on thermal parameter choices for building envelopes.