A building and tree resolving modeling framework for simulating , momentum, energy, pollutant dispersion, and moisture budgets in complex urban canopies over a wide range of spatial scales

Understanding the impact of urban form on energy use and evapotranspiration is critical towards evaluating the effectiveness of urban water and energy conservation projects. These projects come in many forms and are implemented at the individual lot scale. In general, they have goals of improving urban microclimate, reducing energy and water use, and mitigating pollutant emissions. The separation in length scales between the implementation of these projects and the processes that they seek to modify results in a general lack of knowledge about their impact on urban microclimate. Current models that can include important regional scales do not include detailed resolved local effects and therefore, have a limited ability to evaluate conservation projects. Other models can resolve three-dimensional urban geometry on a highly refined grid, but are not coupled to realistic meteorological forcing conditions and or cannot include more than a few buildings/trees. We have developed a highly efficient urban and plant canopy microclimate modeling framework that resolves building and tree scales across urban landscapes. This model is currently being coupled to the Weather Research and Forecasting (WRF) community model to establish the link between small- and large-scale features. Here, we will discuss the general framework and new submodels for the urban energy and water budgets. In particular, we will provide an overview of the main components of this new system called QUIC-EnvSim (Quick Urban Industrial Complex – Environmental Simulation). These components include wind and turbulence fields calculated using the QUIC modeling system, a ray-tracing based radiation model that explicitly calculates the impact of buildings on radiative fluxes, an urban tree model that explicitly includes the impact of trees and their interaction with the built environment and local micrometeorology, a heat and moisture advection model that explicitly computes the exchange of energy and water due to turbulence transport in the urban environment, and a land surface model that calculates the surface energy and moisture budgets over a wide variety of urban surface types (concrete, grass, asphalt, etc.) and the diffusion of heat and moisture into these surfaces. All of these components have been implemented using graphical processing unit (GPU) computing to provide an efficient system capable of calculating the complex interaction between energy and water and the built environment.