The Vertical City Weather Generator

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Moradi, Mohsen
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University of Guelph

The increased rates of urban expansion and replacement of natural areas by artificial surfaces have drastically changed the land use and land cover, and consequently have brought numerous environmental issues at various scales. Urban climate models can predict the environmental impacts of cities through incorporating energy, mass, and momentum analyses. A comprehensive simulation of urban climate requires adequate representation of the essential physical processes that involve exchanges of momentum (via drag), heat (via radiation, convection, and conduction), and water (via precipitation, evaporation, or evapotranspiration) between the atmosphere and the impervious, vegetated, or soil surfaces. In this thesis, a new urban microclimate model, called Vertical City Weather Generator (VCWG), is presented, which attempts to overcome some limitations in the previous studies. It consists of a rural model, an urban vertical diffusion model, a building energy model, a radiation model with trees, an urban surface energy balance model, and an urban hydrology model. VCWG models the dynamic interaction between the mentioned sub-models to resolve vertical profiles of climate variables, including temperature, wind, and specific humidity; to compute temperatures and water content in urban surfaces and sub-surfaces; to compute building environmental variables such as indoor temperature and specific humidity; and to compute energy metrics such as building water/energy/electricity demands and the associated heat or humidity fluxes imposed on the outdoor environment. VCWG is evaluated against the Basel UrBan Boundary Layer Experiment (BUBBLE) field measurements conducted in Basel, Switzerland, in 2001-2002 and the Sunset neighborhood field measurements conducted in Vancouver, Canada, in 2008. The simulation results exhibit reasonable agreement with the measured datasets. The performance of VCWG is further assessed by conducting various explorations on the model’s components, which are in reasonable agreement with the previous studies. VCWG can be used as a design, prediction, or investigation tool to understand how urban climate variables are influenced as a function of forcing environmental conditions and urban configurations. It can be used for simulations to provide details at micro-scale, while it is very computationally-efficient and suitable for large spatio-temporal scale analyses.

Climate Change, Micro-climate Modeling, Urban Canopy Modeling, Urban Climate, Urban Hydrology, Building Energy
Moradi, M., Dyer, B., Nazem, A., Nambiar, M. K., Nahian, M. R., Bueno, B., Mackey, C., Vasanthakumar, S., Nazarian, N., Krayenhoff, E. S., Norford, L. K., and Aliabadi, A. A.: The Vertical City Weather Generator (VCWG v1.3.2), Geosci. Model Dev., 14, 961�??984,, 2021.