Faithful modeling of interaction between flow and urban canopy is a key step to describing the water, heat and momentum transport in the urban atmospheric boundary layer. However, most Large Eddy Simulation (LES) codes for the atmospheric boundary layer are limited to cube shaped buildings on the flat land surface. The Immersed Boundary Method (IBM) as implemented at UCSD can be used to simulate flow around any obstacle without changing the pseudospectral numerical method on the cartesian grid. The Lagrangian dynamic Subgrid-scale (SGS) is implemented to model the effect of the unresolved scales on the resolved LES flow field through local scale-dependent auto-calibration of the Smagorinsky coefficient.

Numerical simulations of the flow over an urban canopy immersed into a two-dimensional sinusoidal land surface and were carried out. The effect of critical parameters such as building height to hill height and building spacing to hill spacing on the flow in and above the urban canopy was examined.