De Ridder, K., Lauwaet, D. and Maiheu, B. (2015) 'UrbClim – a fast urban boundary layer climate model'. VITO, Mol, Belgium. Research manuscript.

UrbClim turns the urban atmosphere into an object that can be compared at a scale wider than the individual street but finer than conventional regional climate modelling. Its operation is selective simplification: an urban land-surface scheme, with representations of imperviousness, albedo, heat storage, roughness and anthropogenic heat, is coupled to a three-dimensional atmospheric boundary-layer model. Validation against observations from Toulouse, Ghent, Antwerp and Bilbao shows that this reduced architecture can reproduce important urban–rural climatic contrasts while running far faster than more elaborate mesoscale models. Its achievement is not an exhaustive reproduction of street-level experience; it is to make long integrations across urban domains computationally practicable. That distinction matters. Model resolution is an epistemic bargain, not a measure of observational completeness. A distributed European study could use such modelling to describe comparable background conditions, but must not mistake a grid-cell prediction for the microclimate a pedestrian encounters under a particular tree, beside a wall, or at a particular hour.