Asymmetries in Urban Weather Generator for Climate-responsive Design: The effect of vegetation on urban heat island

The Urban Weather Generator (UWG) is a widely utilised tool for modelling the influence of urban fabric on climate variables, recognised for its reliability. However, recent studies suggest limitations in its ability to accurately represent the effects of vegetation, particularly trees. This paper evaluates the potential and constraints of UWG, comparing versions 4.1 for Matlab and the Grasshopper plugin Dragonfly. Real and hypothetical scenarios with significant vegetation increases were analysed, revealing the model's limited sensitivity to vegetation changes in dense urban settings. Simulations showed minimal air temperature variations, indicating that while other parameters influence the Urban Heat Island (UHI), the limited representation of vegetation restricts its application in design scenarios. The difficulties in assessing the effect of greenery on the urban microclimate do not seize the opportunity of digital tools to propel performance-based climate-responsive design.